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240 Franz Barthelmes
Friday, September 08. 2017 11:40:15 UTC
Dear Yan, dear Prahladh, thank you for using our service. We try our best to answer questions. However, let me ask you: did you read our answers to frequently asked questions (FAQ) (see buttons on the left)? The article about global models could also be helpful (link at the main ICGEM-site): http://icgem.gfz-potsdam.de/GlobalModelsEncyclopedia.pdf Best regards Franz
239 prahladh kindangi
Friday, September 08. 2017 09:50:11 UTC
Hi ICGEM how can i calculate the grid space interval and i want to download gravity bouguer anomaly with half kilometer interval, please help me in this regarding and also i want to known which model is suitable for regional studies.
238 Yan
Thursday, September 07. 2017 02:52:39 UTC
Hi ICGEM: What is the formula for calculating the force of gravity? Best regards Yan
237 Qi
Thursday, September 07. 2017 01:31:37 UTC
Dear Franz, Sorry, I misunderstand the file. Thank you for the reply. Regards Qi
236 Franz Barthelmes
Wednesday, September 06. 2017 10:10:59 UTC
Dear Qi, sorry, I do not understand your question - maybe I'm too old (I use computers for more than 40 years) :-( . The *.gdf files are pure ascii text files. To open it you can use any plain text editor you like. What do you mean with "projection of the file" ? Best regards Franz
235 Qi
Tuesday, September 05. 2017 12:12:58 UTC
Hi ICGEM, I used the calculation service to obtain the EIGEN-6C4 Geoid. After the calculation, I downloaded a .gdf file. Could you tell me how can I open/load this file, particularly with matlab. In addition, what's the projection of the generated gdf file. Thanks. Qi
234 Franz Barthelmes
Monday, September 04. 2017 10:07:22 UTC
Dear Yan Zhixue, on our website (calculation service) the functionals "height_anomaly" and "height_anomaly_ell" are described as: height_anomaly: The so called "height anomaly" is an approximation of the geoid according to Molodensky's theory. It is equal to the geoid over sea. Here it will be calculated, as defined, on the Earth's surface approximated by Bruns’ formula on the ellipsoid plus a first order correction (eqs. 81 and 119 of STR09/02). height_anomaly_ell: The height anomaly can be generalised to a 3-d function, (sometimes called "generalised pseudo-height-anomaly"). Here it can be calculated on (h=0) or above (h>0) the ellipsoid, approximated by Bruns’ formula (eqs. 78 and 118 of STR09/02). Please let us know, what is unclear. As well as any gravity field model the normal potential can be represented as a spherical harmonic model plus the centrifugal potential. The spherical harmonic coefficients of the normal potential WGS84 are (in icgem-format): gfc 0 0 1.000000000000000E+00 gfc 2 0 -4.841667749599428E-04 gfc 4 0 7.903037334041510E-07 gfc 6 0 -1.687249611016718E-09 gfc 8 0 3.460524681471410E-12 gfc 10 0 -2.650022244590134E-15 These coefficients (plus the centrifugal acceleration) are used to compute the normal gravity for points lying above the ellipsoid (h>0). Best regards Franz
233 Yan Zhixue
Thursday, August 31. 2017 01:47:55 UTC
Dear ICGEM: What's the difference between height anomaly and height anomaly_ell? Best regards, Yan Zhixue
232 Yan Zhixue
Thursday, August 31. 2017 01:28:45 UTC
Dear ICGEM team: What is the normal gravity calculation formula for GNSS points in the equation of elevation anomaly? Kind regards,
231 João Motta
Saturday, August 12. 2017 23:53:39 UTC
Thanks for letting us now. Best regards, João
230 Elmas Sinem INCE
Tuesday, August 08. 2017 09:08:26 UTC
Dear all, Thank you very much for your messages. Currently, we are experiencing some technical issues with our server due to a power outage occurred on August 1 on the entire campus. We are expecting to fix this issue by August 15th. We are sorry for any inconvenience this situation may create and we would be more than happy to help if further assistance is needed. Best regards, ICGEM team
229 Joao Motta
Monday, August 07. 2017 22:11:10 UTC
Hi ICGEM maintainers. I am experience a shortage in the system since August 5. After inserting the parameters (e.g. defining area, degree/order, ...) an click to calculate the system goes 'waiting' with no response. Everytime I go to the calculation service for retrieving information I got stuck, even changing the model, parameters and functional. I tried from different computers and connections so I imagine it has something to do with the system itself. Is anyone reporting this as well? Cheers.
228 Cahyo Nugroho
Monday, August 07. 2017 04:12:57 UTC
Dear ICGEM, I would like to use the calculation services. Unfortunately it doesn't work. It only says 'waiting' without giving any progress. What could go wrong? Thank you. Best regards, Cahyo Nugroho
227 Agustina Pesce
Saturday, August 05. 2017 17:54:55 UTC
Dear ICGEM team. The Calculation Service is not working. Isthis possible? When will it be fixed? Regards, Agustina PEsce
226 Franz Barthelmes
Tuesday, July 04. 2017 11:15:51 UTC
Dear Judith, a sharp cut of the model will affect the computed geoid undulations. If the resulting oscillations are strong depends on what is "strong" :-) . The best way is probably (and this is my advise) to try it out. Compute the geoid undulations with sharp cut (Nmax = 89) and with different values for gentlecut. E.g. from 89 to 100, from 89 to 110, from 89 to 120 ... However, in doing so, not all wavelengths shorter than related to degree 89 are filtered. This is always the compromise of low-pass filtering: (1) sharp cut in the frequency domain but oscillations in the spatial domain (2) smooth cut (smooth transfer function in the frequency domain) with (unwanted) damping of wavelengths of the signal and (unwanted) "let through" of noise. Sorry for my late response. Kind regards Franz
225 Judith Flamme
Monday, June 26. 2017 08:21:13 UTC
Dear Dr. Franz Barthelmes, i was wondering about the parameters (gentle cut, max value) I can choose if i want to have a geoid (EGM2008) calculated only up to degree 89 (complete, the cut must be after this value) and without oscillations... Do you have any advice on that subject ? In case of a sharp cut, will the oscillations strongly affect the geoid, or not ? Thanks for helping me, Kind regards Judith Flamme
224 Franz Barthelmes
Wednesday, June 14. 2017 08:33:23 UTC
Dear Vassilios, please type the value for the grid step first with as many digits as necessary for you. Then it will be possible to write the values of the grid selection with the same number of digits. Best regards Franz
223 Vassilios D. Andritsanos
Wednesday, June 14. 2017 07:02:06 UTC
Dear Dr. Barthelmes. I noticed that the coordinates in the grid selection in the calculation service can be written with rounding up to the second digit after the decimal point while the grid spacing can be written without rounding (e.g. 0.083333333333). Is it possible to provide to the calculation service a grid with more than 2-digits rounding? Thank you in advance for you help. V.D. Andritsanos
222 Franz Barthelmes
Monday, June 12. 2017 08:19:53 UTC
Dear Ngole Moses, the format of the models is very simple (I think it is self-explanatory). You can read it with any text editor which can read plain text. Are you really not able to write a little software to read (or extract) the coefficients? A description of the format is here: http://icgem.gfz-potsdam.de/ICGEM-Format-2011.pdf Best regards Franz
221 Ngole Moses
Friday, June 09. 2017 17:04:53 UTC
How extracts records m n C s and sigma C of GOCO05c.gfc using matlab code or otherwise
220 Franz Barthelmes
Thursday, June 01. 2017 13:27:32 UTC
Dear Ojima Apeh, some (but not all) functionals can be calculated for different heights. Please see the description of the functionals on the calculation service. Unfortunately the input for the height over ellipsoid is active in any case. For the functionals which can not be computed at different heights the value will be ignored. Concerning the zero degree term please read the FAQs. Best regards Franz
219 Apeh O.I.
Wednesday, May 31. 2017 17:37:29 UTC
Dear Barthelmes, Thanks for your kind response. In calculating geoid heights using ETOPO1-2250(topography_shm) on WGS84 reference ellipsoid; (1) Is it necessary to input value for the 'height over the ellipsoid' and what is(are) the implications? (2) Should the Zero Degree Term checkbox remain 'checked' or should be 'unchecked' and what is(are) the implications? Simply put, how was ETOPO1-2250 used to calculate geoid heights used for calculating gravity_Anomally_Bg taking cognisance of 'height over the ellipsoid' and Zero Degree Term? Best regards
218 Franz Barthelmes
Monday, May 29. 2017 11:28:28 UTC
Here is the link to the Spherical Harmonic Coefficients for Earth's Elevation (Coeff_Height_and_Depth_to2190_DTM2006.0.gz - 49 MB) On the page: http://earth-info.nga.mil/GandG/wgs84/gravitymod/egm2008/first_release.html you find: http://earth-info.nga.mil/GandG/wgs84/gravitymod/egm2008/Coeff_Height_and_Depth_to2190_DTM2006.0.gz
217 Apeh O.I.
Friday, May 26. 2017 11:47:11 UTC
Really, you are rendering a great service. Please, can you send me a link on how to download DTM2006(for a given area of study) that you used for calculating the topography model for the GGMs. I want to carry out a terrain correction on some points to see if there will be significant improvement in the Bouguer anomaly. Best regards
216 Sven Reißland
Monday, May 22. 2017 15:02:26 UTC
Dear Aslınur, the G3-Browser will be renewed also. It should happen in the next two to three months. Best regards, Sven Reißland
215 Aslınur
Friday, May 19. 2017 21:38:58 UTC
Dear ICGEM researchers, I see that the website has been renewed but I could not find the G3 Browser. Is it temporary, where or when can I reach the G3 Browser? Best regards Aslınur
214 Daniel Arana
Tuesday, May 16. 2017 22:49:25 UTC
Dear ICGEM team. The link "http://icgem.gfz-potsdam.de/vis3d/gravity-field-tutorial.pdf" is not working. Regards, Daniel Arana
213 Abdel-Rahim
Sunday, April 02. 2017 15:13:23 UTC
Dear, Dr.Franz Barthelmes Thanks again for helping me What does it mean: The main Contributions of static solutions for the satellite-only model have been described the: unconstrained static solution or Kaula regularized (for example: from degree 121 to 200)? The satellite-only gravity field model: ITSG-Grace2014 (Mayer-Gürr et. al. 2014), derived from GRACE data and consists of two parts: 1. Unconstrained Static Solution ITSG-Grace2014s ITSG-Grace2014s: unconstrained static gravity field, complete up to degree and order 200. 2. Regularized Static Solution ITSG-Grace2014k ITSG-Grace2014k: complete up to degree and order 200, Kaula regularized from degree 121 to 200. Regards Abdel Rahim
212 Franz Barthelmes
Wednesday, March 29. 2017 08:46:25 UTC
Dear Abdel, usually the global models with a higher maximum degree fits GNSS/leveling points better. You can compare the table on ICGEM (here are the first models sorted according to their fit to all points):
Root mean square (rms) about mean of
GPS/levelling minus gravity field model derived geoid heights [m]
  Model               Nmax    USA      Canada    Europe   Australia   Japan    Brazil      All
                              6196      2691      1047       201       816      1112      12036
EIGEN-6C4             2190   0.247 m   0.126 m   0.121 m   0.212 m   0.079 m   0.446 m   0.2359 m
EIGEN-6C3STAT         1949   0.247 m   0.129 m   0.121 m   0.213 m   0.078 m   0.447 m   0.2364 m
GECO                  2190   0.246 m   0.131 m   0.123 m   0.216 m   0.080 m   0.451 m   0.2370 m
EIGEN-6C2             1949   0.249 m   0.129 m   0.123 m   0.214 m   0.080 m   0.445 m   0.2373 m
EIGEN-6C              1420   0.247 m   0.136 m   0.128 m   0.219 m   0.082 m   0.448 m   0.2380 m
EGM2008               2190   0.248 m   0.128 m   0.125 m   0.217 m   0.083 m   0.460 m   0.2395 m
GOCO05C                720   0.262 m   0.154 m   0.138 m   0.221 m   0.217 m   0.445 m   0.2539 m
GIF48                  360   0.319 m   0.209 m   0.229 m   0.236 m   0.275 m   0.474 m   0.3055 m
GGM05C                 360   0.321 m   0.213 m   0.225 m   0.239 m   0.282 m   0.461 m   0.3055 m
EIGEN-51C              359   0.335 m   0.234 m   0.248 m   0.234 m   0.312 m   0.476 m   0.3218 m
EIGEN-5C               360   0.341 m   0.278 m   0.266 m   0.244 m   0.339 m   0.524 m   0.3423 m
EIGEN-GL04C            360   0.339 m   0.282 m   0.309 m   0.244 m   0.321 m   0.541 m   0.3464 m
GGM03C                 360   0.347 m   0.337 m   0.301 m   0.259 m   0.316 m   0.513 m   0.3566 m
EIGEN-CG01C            360   0.351 m   0.335 m   0.349 m   0.263 m   0.351 m   0.543 m   0.3682 m
EIGEN-CG03C            360   0.346 m   0.373 m   0.337 m   0.260 m   0.326 m   0.534 m   0.3702 m
GO_CONS_GCF_2_TIM_R5   280   0.398 m   0.310 m   0.343 m   0.336 m   0.450 m   0.505 m   0.3900 m
ITU_GGC16              280   0.398 m   0.310 m   0.343 m   0.335 m   0.450 m   0.505 m   0.3900 m
GOCO05S                280   0.399 m   0.308 m   0.344 m   0.335 m   0.450 m   0.505 m   0.3902 m
Nevertheless, meanwhile the satellite-only models are rather good due to the GOCE mission. Remember, the model EGM2008 do not contain GOCE data (because it has been computed earlier). Compared to the other regions, your rms differences of 0.870 m (EGM2008) and 0.894 m (GOCO05s) for Egypt implies that there are probably some errors in the GNSS/leveling data. Best regards Franz
211 Abdel-Rahim
Friday, March 24. 2017 16:25:14 UTC
Dear, Franz Barthelmes Are the maximum degree and order of spherical harmonic model are the best from the lower? I used the combined model EGM2008 [Pavlis et al. 2012], with the maximum degree and order 2190, and the satellite-only model which called GOCO05s [Gürr et al. 2015], with the maximum degree and order 280, in Geoid modeling in Egypt. The resolution of EGM2008 about 5 Arc-minutes (≈ 9 km) globally, but I know that the Egyptian gravity data which have been used to establish the EGM2008 about 15 Arc-minutes (≈ 27 km) Corresponding to 720 degrees. The computation of the satellite-only model GOCO05s, no terrestrial gravity data used, because it’s the satellite-only model. Comparisons in Egypt, using the EGM2008 and GOCO05s model, have been carried out in terms of geoid undulations, where the geoid heights were computed from the both models and compared against the geoid heights with respect to the GPS/leveling stations. The results were as follows: The average and the RMS difference are 0.225 m and 0.870 m, respectively in case of EGM2008 The average and the RMS difference are 0.136 m and 0.894 m, respectively in case of GOCO05s What does mean that the average in case of the satellite-only model GOCO05s better than the high degree model EGM2008, although the EGM2008 contains terrestrial gravity data for Egypt? Regards Abdel Rahim
210 Franz Barthelmes
Thursday, March 23. 2017 14:43:30 UTC
Recollection Imagine the 3 gravity fields: (1) gravity field of the Earth, described in the rotating Earth fixed coordinate system, under the assumption that Moon and Sun do not exist ==> tide free gravity field model (2) gravity field of the Earth, described in the rotating Earth fixed coordinate system, plus the gravity fields of the Moon and the Sun averaged over a long time (which is called the permanent tidal effect), plus the effect of Earth's deformation, caused by Moon and Sun, on the gravity field (also averaged over time) ==> mean tide gravity field model (3) gravity field of the Earth, described in the rotating Earth fixed coordinate system, without the gravity fields of the Moon and the Sun, but, with the indirect effect of Earth's deformation ==> zero tide gravity field model The differences of these three gravity fields can be described (as the gravity field itself) in terms of spherical harmonics. Strictly, these spherical harmonic series go up to infinity. But, because the permanent (i.e. averaged over time) tidal effects change the gravity field only very globally, it turned out that it is sufficient to change only the coefficient C20, which describes the flattening of the equipotential surfaces of the gravity field.
209 Abdel-Rahim
Monday, March 20. 2017 10:38:58 UTC
Why use the coefficient C2,0 to Conversion between different permanent tide systems in any spherical harmonics model?
208 Abdel-Rahim
Thursday, February 02. 2017 11:23:38 UTC
Dear, Franz Thanks you very much for helping me, and I hope very much that in the following I want to get more information about applications and use of global gravity field models in Geodesy or in general . Regards Abdel Rahim
207 Franz Barthelmes
Wednesday, February 01. 2017 18:36:59 UTC
There are three tide systems that are considered in the computation of a geoid model (see, e.g., https://cddis.nasa.gov/926/egm96/doc/S11.HTML). The geoid in the three systems can be summarized as follows: • Tide-free (or nontidal): This geoid is considered for a tide-free Earth with all (direct and indirect) effects of the Sun and Moon removed. • Mean-tide: This geoid is considered in the presence of the Sun and the Moon (or, equivalently, if no permanent tidal effects are removed). • Zero-tide: This geoid is considered if the permanent direct effects of the Sun and Moon are removed, but the indirect effect component related to the elastic deformation of the Earth is retained. The transformation between the different tide systems in our Calculation Service only changes the coefficient C 20
206 Abdel-Rahim
Sunday, January 29. 2017 19:02:03 UTC
What is meant of: the spherical harmonic model of the Earth's gravitational field have been described as different tide systems such as Tide free, zero tide and mean tide? More clarification is needed.... how it's done
205 Clauri
Saturday, December 10. 2016 04:25:47 UTC
i would like to ask about how many way, WGS2008 is generated, i mean may be by directly measured terestrially or by sattelite or as combination.THx
204 Franz Barthelmes
Monday, September 19. 2016 16:36:45 UTC
Dear Yawen She, why do you think that the differences between gravity_anomaly_sa and gravity_anomaly calculated with our service are to big? How big are they in your computation? The formulas for the computation are described in our STR 098/02, available at: http://icgem.gfz-potsdam.de/ICGEM/theory/str-0902-revised.pdf The formulas for the gravity anomaly according to Molodensky (functional "gravity_anomaly") are (31),(32),(101) and (121) to (124). The formulas for the gravity anomaly in spherical approximation (functional "gravity_anomaly_sa") are (100) and (126). The differences between both for the model EIGEN-6C2 are shown in figure (14). They range from min = -189 mgal to max = 302 mgal. Kind regards Franz
203 yawen she
Sunday, September 18. 2016 08:40:14 UTC
Dear researchers: I calculated the gravity_anomaly, gravity_anomaly_sa and geoid with EIGEN-6C4 model by using your calculating service in WGS84 reference frame. The difference between the gravity_anomaly_sa and gravity_anomaly should be due to the geoid as your description. However, the large difference between these two anomalies cannot be explained by the geoid. Thus, I wondered that is the calculation of the gravity_anomaly is right?
202 Franz Barthelmes
Monday, September 12. 2016 10:18:41 UTC
Dear Abdel-Rahim, I will contact you by email. Best regards Franz Barthelmes
201 Abdel-Rahim
Friday, September 09. 2016 05:54:08 UTC
What is meant by Anomaly degree variances of Global Geopotential Models? Anomaly degree variances and error degree variances used to Evaluation of the Global Geopotential Models to choose the best for geoid determination or others applications
200 Franz Barthelmes
Tuesday, April 19. 2016 07:57:39 UTC
Dear Eugenia, the monthly Equivalent Water Heights (EWH) at the G3 Browser are computed from the spherical harmonic coefficients of the monthly models minus the coefficients of a mean model (EIGEN-6). These difference-coefficients can be used after filtering or without filtering. The formulas for computing EWH from spherical harmonic coefficients of a gravity field model are described in: Wahr, J., M. Molenaar, and F. Bryan (1998), Time variability of the Earth's gravity field: Hydrological and oceanic effects and their possible detection using GRACE, J. Geophys. Res., 103(B12), 30205–30229, doi:10.1029/98JB02844. and John M. Wahr Time-Variable Gravity From Satellites http://igpphome.ucsd.edu/~mrsiegfr/wahr2007.pdf Why do you want to transform EWH into height anomalies? The G3 Browser offers both: EWH and height anomalies. Best regards Franz
199 Maria Eugenia Gomez
Monday, April 18. 2016 17:33:38 UTC
Dear ICGEM team, I was looking into your G3 Browser and I wonder how you estimate the equivalent water hight from you monthly grace models. Which formualtion do you use. And if you can suggest some reading about how to transform equivalent water height into height anomalies. Kind regards, Eugenia
198 Franz Barthelmes
Wednesday, April 13. 2016 12:10:35 UTC
This is an answer to frequently asked questions concerning the computation of the geoid from a gravity field model and the so called "zero degree term". Unfortunately the meaning of "zero degree term" is not unique. Let's recapitulate what the geoid is and how it will be calculated from the spherical harmonic coefficients of a gravity field model. A spherical harmonic model of the Earth's gravitational field consists of the coefficients Clm and Slm, a value for the geocentric gravitational constant GM, and a value for R. For the model, R is nothing more than a mathematical reference parameter. GM is an essential part of the model, multiplied by the coefficient C00 (which usually is near 1) it is the mass of the Earth as it has been estimated for this model. Additionally the tide system must be known. These values represent the 3-dimensional function of the geopotential W(x,y,z) (outside the masses). The Geoid is one particular equipotential surface of the gravity potential of the Earth. (Remember: the gravity potential is the gravitational potential plus the centrifugal potential). Among all equipotential surfaces, the geoid is the one which coincides with the undisturbed sea surface and its fictitious continuation below the continents. If we know the gravity potential W we know all equipotential surfaces, but we don't know which one is the geoid. To calculate the geoid from a selected model we must know which potential value W = constant = W0 the real geoid has. Therefore, usually the geoid is given as geoid undulations or geoid heights with respect to a reference system which consists of a geometrical rotational ellipsoid (normal ellipsoid) and an associated ellipsoidal normal potential U = U(x,y,z). The geometrical ellipsoid should approximate the real geoid as good as possible (in the least squares sense). The normal potential is defined in such a way that its value on the normal ellipsoid is U = constant = U0 and approximates the real value W0 as good as it is known (at the time when this reference system is defined). Hence, the reference system also defines the value W0 = U0. A reference system is defined by 4 defining parameters, which are usually the following ones: - equatorial radius of the Earth: R - flattening: f - geocentric gravitational constant: GM (mass of the Earth * Newton's gravitational constant) - angular velocity of the Earth: omega In this case U0 is a derived parameter. Sometimes U0 is used as defining parameter instead of GM. ⇒ Consequently, it makes no sense to say: "geoid heights of the model xy (e.g. EGM2008)"We must say: "geoid heights of the model xy with respect to the reference system abc (e.g. WGS84)" Of course, our philosophy is not to change ("improve") any coefficients of the models including the value of GM of the model and not to change ("improve") the defining parameters of the reference system with respect to which the geoid should be calculated. ⇒ our "zero-degree-term" is only caused by different values of GM*C00 of the model, and GM of the normal potential, i.e. the reference system. Sometimes additionally the effect of a new (better) value for W0 (which differs from the reference system's value U0) is included into the "zero-degree-term". But we do not do that because in this case it is not possible to say: "geoid heights of the model xy with respect to the reference system abc. To use an improved value of W0 ( ≠ U0) we think it is better to change the reference system (such that U0 = W0) instead of adding a correction term afterwards. If you want to do so you can use your own reference system (user_defined) in the calculation service of ICGEM.
197 Franz Barthelmes
Tuesday, March 15. 2016 10:18:11 UTC
Dear Peter, this model (GOCO05S) is not a static model. It depends not only on the spatial coordinates (x,y,z) or (radius, longitude, latitude) but also on time. A static model consists of the spherical harmonic coefficients C(l,m) and S(l,m) where l is called degree, and m order. The potential W (of such a static model) at a given position, i.e. W(r,long,lat), is calculated by summing up over degree and order of a spherical harmonic expansion (see, e.g. equation 108 of the report: http://icgem.gfz-potsdam.de/ICGEM/theory/str-0902-revised.pdf ) In the model GOCO05S each coefficient (up to degree and order 100) has a static part, a linear trend with time and a sinusoidal time change with an annual period. If G(t) is a coefficient Clm(t) or Slm(t) its value for the time t is: G(t)=gfct(t0)+trnd*(t-t0)+asin*sin(2pi/T*(t-t0))+acos*cos(2pi/T*(t-t0)) where gfct(t0) is the static part at time t0 trnd is the linear trend asin is the amplitude of the sine-part acos is the amplitude of the cosine-part T is the annual period (Remember that the amplitude and phase of a sinusoidal wave with fixed period can be transformed mathematically into a sine-amplitude and a cosine-amplitude together with the same period) (see also posting 111) "V(t)" in the description of GOCO05S is (in my opinion) misleading. The formula delivers the value of each coefficient for the time t and not the potential which is is denotated by "V". For more details concerning the model GOCO05S contact the authors. I hope this will be helpful (?). Best regards Franz
196 Peter Ntimoah
Friday, March 11. 2016 15:40:33 UTC
Hi There, I would like to thank you so much for the service you provide through ICGEM website. I am doing my research on geoid and gravity field. I am using my own software (in Matlab). I am wondering about GOCO25S geopotential model, how can I solve the following information that are mentioned in the gfc file "To compute a gravity field functional at an arbitrary time t, the expression V(t) = gfct + trnd * (t-t0)/T + acos*cos( 2pi * (t-t0)/T ) + asin*sin( 2pi * (t-t0)/T ) with t0 as the reference epoch and T as the annual period (365.25 d), has to be used. The reference epoch is 2008-01-01 (MJD 54466)" I can not understand it well Your help is much appreciated, Thank you, Peter
195 Jesse Jones
Tuesday, February 23. 2016 21:29:04 UTC
Impressed, a lot of effort and research involved. Keep up the Great work.
194 Ologun Fermi
Friday, January 22. 2016 05:43:56 UTC
It is quiet a good job done here. weldone
193 Wolfgang Köhler
Monday, November 23. 2015 09:18:24 UTC
Dear Duanlin, Mohsen and other ICGEM-users with similar problems, downloading the model gfc-files to your PC with a usual web browser is very easy:
  1. Click the link "Table of Models" on the left navigation tab of our ICGEM-homepage. This opens a table with all global gravity field models.
  2. Then goto the line with the model of your interest and click on the blue link labelled "gfc" in the column "download" with the left mouse button. This opens a new tab on your browser displaying the model gfc-file as text. (Please consider, that downloading models with high maximal degree can take some time, since they are quite large files. So it is preferable to download them as compressed files using the blue "zip" link.)
  3. Then use the button "Save page As" in your browser and write it to the directory, where you want it to be placed on your PC.
That's all. kind regardsW. Köhler (administrator)
192 Duanlin Lin
Saturday, November 21. 2015 09:32:11 UTC
I am intrested in some model in this place,but sometimes I do not know how to donwlode the data in this place.I will be very appreciated if you can sent the Guest Book Formular to me. Thank you.
191 mohsen
Saturday, September 19. 2015 18:02:08 UTC
Hi, How can I open gfc files ??
190 gambhir Singh
Monday, September 07. 2015 09:20:15 UTC
Very good site,It gives us all the information required
189 Franz Barthelmes
Tuesday, June 16. 2015 07:06:43 UTC
Dear Wei You, yes, of course, it is allowed to download all models. It depends on your browser how you manage it. For Firefox the addon "DownThemAll" will do it. Best regards Franz
188 Wei You
Wednesday, June 10. 2015 10:15:19 UTC
Dear experts in ICGEM, Recently, I want to dowoload all the monthly gravity field models from the ICGEM website. But I can only download one file at one time. So how can I download all the files together at one time? Is it not allowed? Thanks. Best regards Wei You 10/6/2015
187 Carol G. Bently
Friday, May 29. 2015 08:28:04 UTC
I enjoy whyour website is uр too. Thіs is some kind of hard and clever wоrk but results into an exposure! Keep up the good work.
186 Carol Bently
Thursday, May 14. 2015 07:38:59 UTC
I'll say this website must be read by others. For instance, students that make a research on something like this. It's a big help for them. Thanks.
185 Michael Raftery
Monday, May 11. 2015 12:29:11 UTC
Excellent site. Thank you for all the hard work you do on this important topic.
184 Abdelrahim
Saturday, May 09. 2015 15:25:21 UTC
Hi all, I am a new user of ICGEM. Are all coefficients of all model are fully normalized and unitless Connect Abdel Rahim Ruby Abdel hamid Hassanain Demonstrator Department of Surveying Engineering Faculty of Engineering Shoubra - Benha University Univ. e-mail: abdelrahim.ruby@feng.bu.edu.eg E-mail: abd_roby87@yahoo.com Website: http://www.bu.edu.eg/staff/abdelreheemroby3 108 Shoubra St. - Cairo – Egypt Postal Code: 11629 Tel: 01114812396
183 Abdelrahim
Saturday, May 09. 2015 15:18:47 UTC
I have local Gravity Data.....the question here, How to use this data to improve or update Global Gravity Field Models (GGMs)? Like EGM96 or how to combining an EGM with terrestrial data Connect Abdel Rahim Ruby Abdel hamid Hassanain Demonstrator Department of Surveying Engineering Faculty of Engineering Shoubra - Benha University Univ. e-mail: abdelrahim.ruby@feng.bu.edu.eg E-mail: abd_roby87@yahoo.com Website: http://www.bu.edu.eg/staff/abdelreheemroby3 108 Shoubra St. - Cairo – Egypt Postal Code: 11629
182 Franz Barthelmes
Tuesday, May 05. 2015 09:08:25 UTC
Dear Craig, it is always the same problem with "reduced" gravity data. They are reduced somehow and nobody knows exactly how :-) . If you know the reductions, than you can use the table with the descriptions of the functionals (at the site "calculation service") to find out which is the best functional. Or reverse all reductions. The result should be the full measured gravity value at the defined coordinates at the Earth surface (ellipsoidal lat, long, height). The according functional is "gravity_earth". Or reverse all reductions and subtract the normal gravity for the same coordinates (including ellipsoidal height!). The result should be the gravity disturbance at the Earth's surface. The according functional is "gravity_disturbance". Or reverse all reductions and subtract the normal gravity for the same lat. and long. but at the telluroid (Earth's surface minus height anomaly). The result should be the gravity anomaly according to Molodensky's theory. The according functional is "gravity_anomaly". Or reverse all reductions and apply the free air reduction down to the geoid and subtract the normal gravity computed at the ellipsoid (same lat. and long). The result should be the classical gravity anomaly. (Maybe your terrestrial data are reduced in this way?) The according functional is "gravity_anomaly_cl". The exact free air reduction should be the exact downward continuation. Usually it will be approximated by dg/dh * H and, hence, it will be not exact. The classical gravity anomaly can be approximated by the spherical approximation (the differences of some approximations are shown in STR 09/02 available on the ICGEM site). The usual definition of the simple Bouguer anomaly is: classical gravity anomaly minus the attraction of the Bouguer plate. Because the difference of the classical gravity anomaly and the spherical approximation of the gravity anomaly is much smaller than the uncertainty (the error) of the influence of the Bouguer plate, we use the spherical approximation to compute the "gravity_anomaly_bg". So, you see, there are different possibilities to compare measured and reduced "gravity data" with computed ones :-) . Kind regards Franz
181 Craig Miller
Monday, May 04. 2015 18:10:19 UTC
Hi Many thanks for providing this service! I have a couple of questions about the EIGEN6C4 model functionals. I would like to use these functionals to provide "regional" data for a terrestrial data set I have. My terrestrial data is reduced using modern ellipsoid based formulas and heights. Which of the model functionals would be the closest approximation of terrestrial freeair data reduced using ellipsoid heights? Secondly in your description of the gravity_anomaly_bg functional you say that " ... it will be calculated by the spherical approximation of the classical gravity anomaly minus 2πGρH". I'm confused by the "spherical approximation of the classical anomaly" bit. In the description of the spherical approximation (gravity_anomaly_sa functional) it states that it is reduced to the ellipsoid, however the classical anomaly description says it is reduced using the geoid. Is this a contradiction or have I missed something? Finally, I don't expect the terrestrial data and model functionals to be exactly the same, but over a small area (say 50 x 50 km) would you expect the difference to be a simple DC offset or a more complicated shape. ie would it be possible to merge the terrestrial and EIGEN6C4 data sets or should they be treated individually? Regards Craig
180 Michael E. Chapman
Thursday, April 30. 2015 03:08:42 UTC
This is an absolutely marvelous service. Keep up the good work!!
179 Franz Barthelmes
Wednesday, April 15. 2015 10:52:46 UTC
Dear Abdelrahim, I will contact you per e-mail. Kind regards Franz
178 Abdelrahim
Wednesday, April 15. 2015 08:54:19 UTC
How development Global Gravity Field Models like EGM96? I have some questions about Global Gravity Field Models (ICGFM). Where How to Calculate Coefficients of this model? I.e. I need the program to compute spherical harmonic analysis of EGM model.
177 Guy Bouyrie
Tuesday, April 07. 2015 09:39:29 UTC
A wonderful job that allows no longer make use of Java JRE ! Thank you ! Guy Bouyrie UdPPC - Bordeaux (France)
176 Li Yongsheng
Monday, March 16. 2015 04:57:53 UTC
175 Tadesse Tujuba
Wednesday, March 11. 2015 07:52:57 UTC
Dear Sir, You are offering a very nice service freely. That is great. I want to use the Java Applet free service. How can I use it? Thank you
174 Franz Barthelmes
Monday, March 02. 2015 10:59:46 UTC
Dear John Ryan, I use the GMT-routine xyz2grd to convert the ICGEM-grids into GMT-grids. There are many examples and tutorials about GMT on the net. Kind regards Franz
173 John Ryan
Tuesday, February 24. 2015 22:52:59 UTC
Thank you very much for providing this resource to the research community! As you do for the Image-File option in the model calculation utility, I would like to use GMT and be able to use different map projections. For this purpose it would be very helpful to learn about (1) converting the gdf file into something GMT can read, and (2) example GMT script(s). Is this information available somewhere on the web site?
172 Franz Barthelmes
Friday, January 16. 2015 13:24:58 UTC
Dear Hakim SAIBI, I will contact you per e-mail. Kind regards Franz Barthelmes
171 Hakim SAIBI
Thursday, January 15. 2015 00:38:32 UTC
Hi all, I am a new user of ICGEM. I want to generate monthly Bouger anomaly maps. Please help me with one example. Thanks
170 Jessica
Wednesday, November 26. 2014 22:22:36 UTC
error: connection to ICGEM: server at port 1891 could not be established.
169 Wolfgang Köhler
Tuesday, November 11. 2014 11:01:23 UTC
Dear Dawit, in principle, this should be no problem. Do you have any suggestions? kind regards W. Köhler (administrator)
168 Dawit
Tuesday, November 11. 2014 10:08:40 UTC
Hi Sir/Madam, I have just visited your webpage and was impressed with contents and practical applications in water resources management. Do yo mind expanding the list of basins in Australia? Thanks Dawit
167 Wolfgang Köhler
Friday, November 07. 2014 07:49:47 UTC
Dear ICGEM users, Oracle's new security policy since Java version 8 by default inhibits the TCP connection to our server socket, which is the basis of our service. Without this connection no data transmission between server and client works. If possible, avoid upgrading to Java 1.8! Please note, that our ICGEM service never requests a Java update - such requests are always originated by your internet browser. If you have to upgrade anyway, we can offer an intermediate solution, to circumvent this problem. However, that requires some administrative action on your client computer. You have to modify the central 'java.policy' file on your PC (see also java.net.SocketPermission in Applets). It is not very simple to find and edit this file under Windows, but this modification solves the problem. The actual location of this file depends on your operating system and Java version, it is something like "C:\Program Files\Java\jre7\lib\security\java.policy" (or similiar, eg. C:\Program Files (x86)\Java\jre1.8.0_25\lib\security) and you have to add an entry:
    permission java.net.SocketPermission "*", "connect, accept ,resolve";
to allow your PC the TCP-connection to our ICGEM-server (IP= Here you can download a tested java.policy file. This should work for all Java versions. Wolfgang Köhler (administrator)
166 Ernest Berkman
Thursday, November 06. 2014 15:39:01 UTC
It appears as if you are using Java Plug-in and I am Using JRE version 1.7.0_65-b20 Java HotSpot(TM) Client VM so the appelet does not run. Any suggestions. Windows 7 64 bit
165 Deepika
Monday, November 03. 2014 04:52:02 UTC
This is great new security policy simply great.
164 Hakim
Thursday, October 30. 2014 00:10:39 UTC
Hello everyone, my name is Hakim Saibi from Kyushu Univ. I am here to use and learn more about GRACE models. Thanks
163 Wolfgang Köhler
Monday, October 20. 2014 06:25:10 UTC
Dear Afri, the same advice as in the last posting given to Arinda (just below in posting 161). Please read the listed references. W. Köhler
162 Afri Yudhawan
Monday, October 20. 2014 02:59:55 UTC
Dear administrator, I have some problems about showing the visualization of geoid. The plugins showed me only a blue sphere. I've installed the newest java version but the site still only shows the blue sphere. Could you help showing the visualization for me, please? Or do you have some advices for me? Thanks for your kindly attention. Afri Yudhawan +6281315126209 Geodesy and Geomatics Engineering Bandung Institute of Technology Indonesia
161 Wolfgang Köhler
Friday, October 17. 2014 09:59:46 UTC
Dear Arinda, please read the information given at the bottom of the visualization page under the topic 'Troubleshouting' and the posting 147 in this guestbook below. If nothing of the hints works for you, please send me an Email. kind regards Wolfgang Köhler
160 Arinda
Friday, October 17. 2014 05:31:59 UTC
Hello, I tried to access this site for my lecture assignment. I need to see geoid model in visualization part. But, I just saw blue sphere although I've tried it over 10 times. Could you please tell me, is it something wrong with my laptop or my connection. I've tried some connection, but it didn't help. Thank you, I hope for your kind response. Sincerely, Arinda
159 Tang Kieh Ming
Thursday, October 16. 2014 23:28:04 UTC
Dear, After finish computing and unable to get gridfile from calculation services. Any solution? Thks & Rgds. kiehming
158 Franz Barthelmes
Monday, August 11. 2014 08:07:52 UTC
Dear Petros, our service offers the possibility to compute the topography from a spherical harmonic model or from the etopo1 grid (as described in the table on the calculation service site). It doesn't offer the calculation of the gravitational attraction of these topography. Kind regards Franz
157 Petros Manousakis
Friday, August 08. 2014 04:53:04 UTC
Dear administrators, It is the second time I contact you. The first time was by email about a problem I had and your answer had been very helpful! This time, I would like to ask if your applet could calculate the topographic correction (TC) in grid fore some region,(e.g. using a topography model), so to use it in Remove-Restore method. If not, is there an internet site that does it so? Thank you in advance, Petrow Manousakis
156 Franz Barthelmes
Monday, July 21. 2014 06:36:01 UTC
Dear Victorino Garcia, please see postings No. 142 and 143. Kind regards Franz Barthelmes
155 Ramon Garcia
Friday, July 18. 2014 13:37:48 UTC
This website is great. One can evaluate practically any GGM produced so far. Would be very helpful if you allow to evaluate the GGMs for not gridded points, so one can only put the coordinates file to get the geoid or other functions of the geopotential. Or, Could you tell me where can I get a program to do this type of geoid evaluations. Thanks Victorino Garcia
154 Franz Barthelmes
Friday, July 18. 2014 08:03:06 UTC
Dear Sai, it is a little difficult for me to understand what you mean. The details of the computation of the monthly solutions are documented in the Report: http://ebooks.gfz-potsdam.de/pubman/item/escidoc:108022:2/component/escidoc:108023/1202_rev_ed.pdf?mode=download (also available on the ICGEM-Site "Models from Dedicated Time Periods"). Yes, the monthly solutions also contain the change in gravity (or geoid heights, or equivalent water heights) before and after big earthquakes. A good idea to get an overview if such effects are visible is the use of one of the tools: http://www.thegraceplotter.com/ or http://icgem.gfz-potsdam.de/Google-Plotter/Grace_Plotter.html If you put the marker, e.g., at the position near the big earthquakes in the Sumatra region (end of 2004) or near Japan (first part of 2011) you will see the jumps in the graph. Kind regards Franz
153 sai
Thursday, July 17. 2014 08:25:30 UTC
I have a doubt regarding GSM-2 data, it contains dynamic field alone or both static n dynamic(variation due to ocean, atmosphere and geodynamic processes like earthquakes).I want to use this data for calculating gravity variations before and after the earthquake.Please kindly help me in this regard.Thank you very much in advance.
152 Wolfgang Köhler
Monday, June 30. 2014 06:30:48 UTC
Answer to Ajeet Kumar: Please read my posting #147 in this Guest Book below. It should help you solving your problem with Java. Kind regards Wolfgang Köhler
151 Ajeet Kumar
Saturday, June 28. 2014 11:42:53 UTC
My browser does not support Java Applets. To use this applet, How can i Enable Java for my browse I am using Windows 8 , Ram- 4 GB, System Type- 64 bit, Processer -Intel (R) Core TMI i7 37770 CPU @3.4 GHz
150 Franz Barthelmes
Wednesday, May 07. 2014 07:07:53 UTC
Dear Tongong Ayuba Badung, we are a service for global gravity field models and not for gravity measurements. The service for gravity measurements is the Bureau Gravimétrique International / International Gravimetric Bureau (see: http://bgi.omp.obs-mip.fr/ ). Our service ICGEM offers the possibility to compute different functionals (e.g.: gravity, gravity anomalies, gravity disturbances or geoid undulations) from one of the global models on a grid of your choice (see the calculation service of ICGEM). I would recommend to use the most recent combination model EIGEN-6C3stat (which contains satellite data, terrestrial gravity measurements and data from satellite altimetry). If you have questions please contact me. Kind regards Franz Barthelmes
149 Tongong Ayuba Badung
Wednesday, May 07. 2014 04:46:30 UTC
I wish to know more on how to obtain terrestrial gravity data in large quantities covering a large area
148 Joe Olliver
Tuesday, April 01. 2014 10:58:20 UTC
I was very pleased to be able to access the GOCE results on your website after all efforts to cut throught the bureaucratic jungle of the ESA download procedure had failed. Please keep up the good work. Regards Joe Olliver Earth Sciences Oxford University
147 Wolfgang Köhler
Monday, March 10. 2014 09:25:34 UTC
Dear Alberto Benavidez, the problems you mention are due to a new security policy, that Oracle has introduced with the new Java version (7u51) by January 2014. From this version the browser refuses to execute Java applets, which are the basis of our service, by default. The easiest way to fix this problem is to stick (or go back) to older versions of Java (1.6). Another way is to use the Java Control Panel and add our site to the Exception Site List: You may either add all HTML-pages which you want to use (eg. icgem.gfz-potsdam.de/ICGEM/potato/Service.html), or yet better add the Jar-file (which includes all applets of our service) as http://icgem.gfz-potsdam.de/ICGEM/potato/Potato.jar. The third possiblity is to reduce the Java security level to the lowest value. And, last but not least, there are open source alternatives to Oracle's Java, namely "IcedTea". Kind regards Wolfgang Köhler
146 Alberto Benavidez
Sunday, March 09. 2014 23:30:38 UTC
Dear Dr. Frank Barthelmes, I have been working using the ICGEM's resources for some years, as I let you know on May 2012 (Postings 121 and 122). I used Windows XP and Java 6 in my computer. However recently I upgraded them to Windows 8.1 and Java 7. As a result I am able to get a connection with the Calculation Service and the literature and figures of the "Calculation of Gravity Field Functionals on Ellipsoidal Grids" but the location of the form to input request data and obtain the outputs remains blank, and the following error warning appeared: ClassNotFoundException ServiceApplet.class I tested several forms of the command: java -cp, but I coudn't get the correct answer. Do the Calculation Service already have a solution to fix this problem? Sincerely. Alberto Benavidez
145 Franz Barthelmes
Wednesday, February 05. 2014 10:42:57 UTC
Dear Alexander, do you mean GOCE-data in the sense of "measurements" or gravity field models derived from GOCE data? Our service only offers the models and do not offer measurements. Kind regards Franz
144 Alexander Marchenko
Wednesday, February 05. 2014 09:45:46 UTC
Dear Colleagues, More than 10 yr ago I was working into GFZ Potsdam. Today I decided to came back to the LEO satellites, in particular, to the GOCE data processing. Could you help me with GOCE data, since ESA data format require especial transformation or corresponding software. Best regards, Alexander Marchenko
143 Franz Barthelmes
Monday, January 27. 2014 09:26:25 UTC
Dear Ruth, I understand your question. But in our calculation service we only offer the possibility to calculate values on a lat.-long.-grid. Values on a regular grid can be calculated from spherical harmonics much more efficiently than for irregularly distributed points. The software of the calculation service can only produce regular grids. Unfortunately, up to now, we don't have the time to offer the additional possibility to calculate values for irregularly distributed points. Best regards Franz
Friday, January 24. 2014 15:39:55 UTC
Hi, I would like to to make a suggestion about the way we have obtain the values of the functionals on calculation service. I have to obtain the values for specific points, not for a grid. There is no a way to do this quickly, like put an archive *.txt or similar with the coordinates I need and obtain the values. I have to do this point by point, and there are many points, what takes me a lot of time. Could you consider the possibility of doing a function to solve this dificulty? Thank you so much. Yours sincerely, Ruth
141 Grzb
Thursday, November 28. 2013 11:30:52 UTC
Hello from Jarmul's Cave
140 xiaole
Thursday, November 14. 2013 08:17:03 UTC
Thank you very much for the work you have done! And I think the guest book will be usefull.
139 Franz Barthelmes
Monday, May 13. 2013 05:54:22 UTC
Dear Nabila, on the page "Models from Dedicated Time Periods" of our service below the headline "Non-isotropic smoothing and subtracting of a mean model" are the coresponding references. Why do you use release 04? The releases 05 are available and are better! Kind regards Franz
138 Nabila
Sunday, May 12. 2013 11:27:40 UTC
Hi, I'm using GRACE data GFZ release-04 DDK2 for my thesis. But what is DDK2 filter? My supervisor told me to use DDK2 filter, but I can't find clear description about it. Thank you. Nabila
137 Lei Qiu
Friday, December 14. 2012 06:44:05 UTC
service is very good,but it is a little bit slow to open the website
136 Dr. Ioannis Haranas
Wednesday, October 24. 2012 16:34:53 UTC
Very useful site!
135 Franz Barthelmes
Thursday, September 20. 2012 05:38:55 UTC
Dear Stanid Song, the models consist of coefficients of spherical harmonics (search for "spherical harmonics" at google :-) ). L is degree M is Order C stands for even coefficient S stands for odd coefficient sigma stands for standard deviation Kind regrards Franz
134 Stanid Song
Wednesday, September 12. 2012 12:37:42 UTC
what does ¡°L,M,C,S,sigma C,sigma S¡± stand for ?
133 Franz Barthelmes
Monday, September 10. 2012 11:01:30 UTC
Dear Prof. Lopes, thank you for using our service. I am afraid that I did not understand your question correctly. What do you mean with "routine for data manipulation"? You write that you use the harmonic coefficients. For that you need a routine to compute the geoid from the coefficients, thus I guess you have such a routine. Then you write: " however I'm not getting a routine that calculates the model derived from geoid as EINGEN-6C". What do you mean? The gravity field model is the set of coefficients. From this model (i.e. from these coefficients) you can calculate different functionals of the (model of the) gravity field. One functional is the geoid with respect to a defined reference system (there is no "EIGEN-6C-geoid without defining a reference system). You can use our "calculation service" to calculate geoid heights from one of the models (plus a reference system) on a grid of your choice. If you need help in using the calculation service, please let me know. (I will also answer per e-mail.) Kind regards Franz
132 Alexandre B. lopes
Friday, September 07. 2012 16:50:39 UTC
Dear, First I would like to commend the work of ICGEM. It is very good and useful. I'm a user of the geoid models. I use them in determining geostrophic currents in the South Atlantic Generally work with the harmonic coefficients, however I'm not getting a routine that calculates the model derived from geoidas EINGEN-6C. How do I proceed in this case? I leave it as a suggestion to place a routine in FORTRAN for data manipulation. Cordial greetings. Thank you. Alexandre B. Lopes
131 Franz Barthelmes
Friday, July 06. 2012 06:33:07 UTC
Dear Kelly, it is nice to hear that our site is useful for you. Basically our service consists of 3 parts: - collecting of global gravity field models (sets of spherical harmonic coefficients) - visualisation service - calculation service The visualisation service calculates the grid on our computer and transfers it (together with the java program) to your computer. Thus, the visualisation depends on the possibilities of java and the resources of your computer. The calculation service calculates grids on our computer and provides them for downloading. The format of the grids should be (hopefully) self-explanatory. Additionally we offer (tick at PS-File at the bottom of the input mask) a plot of these grids. You can use these grids as input to rendering programs on your computer. All things we offer are based on the global models. The computation, estimation, determination of the global models is not a task of our service. If new data (containing gravity field information) become available (regional terrestrial or global satellite measurements) it could (and will) be used to compute a new improved global model by the groups responsible for that. Then we will include this new model into our service :-) . Thanks again for using our service. If you have further questions, please contact us. Kind regards Franz Barthelmes
130 Wolfgang Köhler
Thursday, July 05. 2012 10:43:46 UTC
Dear Kelly, many thanks for your positive feedback to our service! The problem with the visualization that you mentioned is clearly a memory overflow. Grids of 0.2° or 0.1° require huge amounts of PC-memory (8GB or more) and also a Java-implementation, which is able to use it. I am not quite sure, if I understand your first question correctly, but one option is, to use our "Calculation Service". It allows you, to compute a high-resolution grid (up to 0.1°) of plenty of models and then download it to your computer. Then you can use any rendering program to display it as 3D-surface. Please tell us, if this is what you wanted. The second question, regarding the acceptance of outside gravity data will be answered soon by another collegue of our service. kind regards W. Köhler
129 Kelly Bellis
Thursday, July 05. 2012 07:39:31 UTC
Love this site! THANK YOU!!! THANK YOU!!! If this is the wrong forum for posting these questions, please forgive me, but I'm hoping that others might benefit from this discussion / questions / answers. Aside from getting the PotatoApplet to utterly crash when attempting to render at .2, or it simply freezes (see console transcript below) what I'm searching for is the highest resolution 3D surface available of the most current (static) geoid model so that it might be rendered in another program. Deciding upon the "boost" or level of height exaggeration ahead of that creation like what the PotatoApplet allows would be fantastic. Separately, the second thing I'm curious about is if the ICGEM might accept outside gravity data to model, in particular; gravity data produced through the GRAV-D program. generating sphere with 900x1800 points nt = 1800 Exception in thread "Thread-12" java.lang.OutOfMemoryError: Java heap space at Sphere3D.build_triangles(Sphere3D.java:90) at Sphere3D.(Sphere3D.java:35) at Potato3D.(Potato3D.java:11) at Scene3D.make_potato(Scene3D.java:189) at Scene3D$3.run(Scene3D.java:179)
128 Franz Barthelmes
Friday, June 15. 2012 13:11:03 UTC
Dear Andrew Richardson, I will answer by email. Regards Franz Barthelmes
127 Andrew Richardson
Friday, June 15. 2012 00:38:58 UTC
Hi, My name is Andrew Richardson. I run a Hydrographic survey company in Perth Australia. I have been looking through your Calculation of Gravity Field Functionals on Ellipsoidal Grids on-line applet. What do I need to do, if possible, to replicate N values for Australia. Do the models you provide figures for match in any way the AUSGeoid09. I have been testing values for onshore and offshore and comparing to AUSGeoid09 values and cannot get them to match in any way. Can you explain how the on-line service can provide figure that will be relevant for me. I am just trying to find the Geoid separation between the ellipsoid. Hope you can help Regards Andrew Richardson Director Surrich Hydrographics
126 Franz Barthelmes
Thursday, May 31. 2012 10:54:42 UTC
Answer to the question from Dr.Sanjit Kumar Pal (which could be of general interest) ================================================ Frequently asked questions are: (1) "Which series of monthly models shall be suitable? (for some particular problem)" and (2) "How should I filter these models?" Answer to (1): The software packages of the 3 analysis centres CSR, GFZ and JPL are independent. But they use the same processing standards to generate the GRACE Level-2 products. From point of view of ICGEM it is not possible to say that the models from one centre are better (for some particular problem) than the others. Best idea is to use all 3 and compare them :-) . Answer to (2): The monthly solutions of the 3 centres are produced (basically) unconstrained and are provided without any filtering. The reason is that it depends on the specific application how and how strong filtering is necessary. Only the user can decide how to filter.
125 Franz Barthelmes
Wednesday, May 30. 2012 08:59:52 UTC
Dear Sheda, the transformation between the different tide systems in our software only changes the coefficient C20. The formulas which we use are: c20zt = c20tf + rk*x (zero tide <= tide free) and c20mt = c20tf + (1d0+rk)*x (mean tide <= tide free) with x = -1.39d-8 rk = 0.3d0 Kind regards Franz
124 Dr S K Pal
Saturday, May 26. 2012 11:44:47 UTC
Good afternoon...! This site is scientifically very resourceful I am interested in Satellite Gravity data for possible correlation with earthquake Occurrence/ ground base GPS data of stain accumulation over land I want to fetch one data set of 5 Degree x 5 Degree Gravity data of July,2008 and another set of data of December,2008 over Himalayn Region. 1. Which monthly model(Monthly/JPL-RLl05/JPL-RLl04/CSR-RL05/GFZ-RL04)shall be suitable? 2. Which MODELFILE (filtered models begin with "kfilter_DDK" / "GSM-2")shall be suitable? Thanks to you all. sanjit
123 she.daa
Friday, May 25. 2012 15:11:51 UTC
Hello, thank you for ICGEM help me about result of the calculation. I had a new problem, can I know what description about tide system in calculation services. Tide free, zero tide and mean time. I guest mean tide setting is when the value of the tide halfway between mean high water and mean low water.
122 Franz Barthelmes
Monday, May 21. 2012 07:14:38 UTC
Dear Alberto, on our calculation service site (scroll down on the site) is a short description which formulas we use for the Gaussian Filtering. Gaussian filtering of the gravity field values on the sphere is equivalent (for small filterlength) to multiplying the spherical harmonic coefficients with an appropriate Gaussian function depending on the spherical harmonic degree. That is what we do. More details can be found in: Jekeli, C. (1981), Alternative methods to smooth the Earth’s gravity field, Tech. Rep. 327, Dep. of Geod. Sci. and Surv., Ohio State Univ., Columbus. Kind regards Franz
121 Alberto Benavidez
Thursday, May 17. 2012 22:59:26 UTC
I have been applying your resources in order to calculate the gravity parameters for Uruguay. For such task I mainly use the EIGEN-6C geopotential model (need to say that in the past I did the same job with the GOCE's results). Recently I have been quite interested to filter that data and utilize it in geophysical investigations. Therefore I employed the related gaussian option you offered and obtained several outputs. However I am not completely able to grasp the mathematical procedure and tools (convolution or FFT2D) applied there. For that reason I'd truly appreciate your help to get some information about the topic.
120 Franz Barthelmes
Wednesday, April 25. 2012 10:45:10 UTC
Dear Jaydragon, can you please explain what kind of research do you want to do and which software do you need? Kind regards Franz Barthelmes
119 Leo
Thursday, April 19. 2012 13:25:47 UTC
I want to do some research about the GRACE, where I can get the code of program?
118 Wolfgang Köhler
Wednesday, April 18. 2012 06:58:34 UTC
Dear Sheda, I have checked your last usage of the "Calculation Service" and can find no error on our site. It was the calculation "gif48-174500.inp" with input parameters: ... gridstep 0.0166667 longlimit_west 98 longlimit_east 105 latlimit_south 0 latlimit_north 9 .... The calculated grid "gif48-174500.gdf" was exactly the requested one. It spans the rectangle long=[98.000 - 104.9833] * lat=[9.000 - 0.000]. Also the corresponding PS-file "gif48-174500.ps" seems correct to me. Could you please give us some more information, which calculation actually went wrong? And please (this applies to all requesters) give as reference the name of the calculated file! (The name of the file, which you see after calculation in the yellow status line). This would allow us an easier check. kind regards Wolfgang Köhler
117 she.daa
Tuesday, April 17. 2012 15:53:05 UTC
hello, i had using calculation service for gravity anomaly, my grid is between 1 to 10 for longitude, 1 to 7 for latitude. But the data only calculate the last grid. (10 , 7). I very appreciated if this problem can solve it. Thank you.
116 Franz Barthelmes
Tuesday, April 10. 2012 06:19:54 UTC
Dear Sreejith Kattumadam, thank you for using our service. The "gentlecut"-possibility in our calculation service is described in the document: "Low Pass Filtering of Gravity Field Models by Gently Cutting the Spherical Harmonic Coefficients of Higher Degrees" and can be downloaded at: http://icgem.gfz-potsdam.de/ICGEM/potato/gentlecut_engl.pdf You can cite it by citing the service ICGEM. Kind regards Franz
115 sreejith
Monday, April 09. 2012 10:04:39 UTC
Hi, Can anybody suggest hoew to how to cite the gentlecut_engl.pdf doccument with regards sreejith
114 Igor Protsenko
Monday, December 26. 2011 18:48:35 UTC
Thanks a lot! Gaint job and frendly interface.
113 Wolfgang Köhler
Friday, December 09. 2011 13:13:05 UTC
Dear Sheda, please have a look at our main page ('ICGEM Home'). There you will see under the topic Some ICGEM related documents a link Description of the ICGEM-format There you will find what you need. kind regards W. Köhler
112 she.daa
Thursday, December 08. 2011 13:31:58 UTC
my name is sheda from Malaysia and I'm a degree student at Faculty of planning and surveying-UiTM I'm currently testing global geopotential model(gravity data) with local gravity data. I had download data GGM but I not very understand the format. Is there any format that I should refer it? can I know what is the link? Kind regard, sheda
111 Franz Barthelmes
Friday, November 18. 2011 10:22:19 UTC
Dear Marko, I understand your question and we are aware of the (minor (?)) problem. I think, this is of general interest and I'll try to explain it briefly: Our knowledge about the global gravity field (i.e. the accuracy of the global models) became better and better and now it is possible to calculate not only mean models over a long period of measurements but also time variations of the gravity field. One result is that also models from short time periods (one month or shorter) are calculated and provided to the public. These models have, naturally, lower spatial resolution. On the other hand, the French-German group (GRGS and GFZ), which calculates the EIGEN-models, found that it is possible to use all the available measurements of a long time span to estimate some additional parameters describing time variations without losing the accuracy of the usual (static) coefficients (i.e. without losing the high spatial resolution). As a result the models EIGEN-6S and EIGEN-6C contain, additionally to the (traditional) spherical harmonic coefficients, also some parameters which describe some basic time variations of these spherical harmonic coefficients. These additional parameters are the amplitudes of sine and cosine shaped time variations with annual and semi-annual periods as well as values for the linear trends of all coefficients up to degree and order 50. (Remember that the amplitude and phase of a sinusoidal wave with fixed period can be transformed mathematically into a sine-amplitude and a cosine-amplitude together with the same period). These new parameters are important e.g. for exact orbit calculations or special investigations of time variations of the gravity field. To calculate functionals from such a model, strictly speaking, you have to know for which time you want to have it. Then, in a first step, use the formulas given in the header of the model to calculate the coefficients for the epoch of interest and, in the second step, use the coefficients of this epoch in the same way as for the static models. Up to now the calculation service of ICGEM do not offer this possibility. The main reason (apart from finding time to change the software :-) ) is that I think people who need it have their own software so that only few users will really need it at ICGEM and I'm afraid that all the others could be confused. Simply ignoring these additional parameters will not result in the mean model over the time span of the measurements. It will also not result in the model for the reference epoch (t=t0) because the sinusoidal oscillations (of the two periods) are (in general) not zero at t=t0 (the cosine terms in the formula are 1 for t=t0). It will result in a model from which the annual and semi-annual periods are subtracted (and without trend). This is probably better than a mean model over a time span which is not an integer multiple of the periods. Best regards Franz
110 Marko Pavasovic
Thursday, November 17. 2011 10:18:37 UTC
Dear ICGEM Team, My name is Marko Pavasovic and I'm a PhD student at Faculty of Geodesy - University of Zagreb, Croatia. I'm currently testing global geopotential models by comparing height anomalies obtained from global geopotential modelas (combined solutions) with GNSS/levelling undulations at the territory of our country and having trouble with understanding EIGEN-6C time depended coefficients. For height anomalies computation at exact point with known coordinates from certain global geopotential model I'm using "f477s_B.for" Fortran program written by Professor R.H. Rapp. I don't quite understand which coefficients to use regarding to time depended ones in EIGEN-6C model so can You please help me with that and give me short explanation how to use this model to calculate height anomalies?. Thank You. Winh Kind Regards, Marko Pavasovic
109 Jisun Lee
Thursday, November 10. 2011 12:23:26 UTC
I've sent a e-mail to ask sth about the models. Please check the e-mail having a title of "Question for the result (EGM2008 and EIGEN-6C)"
108 Wolfgang K�hler
Sunday, November 06. 2011 08:30:25 UTC
Dear Leejs, I do not understand exactly, what is the problem. You should open the link 'Table of Models' on the left side. Then you click on the 'Download' button X inside the table, in the model of your choice and you have it on your computer. kind regards wolfk
107 leejs
Sunday, November 06. 2011 07:15:26 UTC
I would like to check the new geopotential model to calculate the local geoid in Korea. Please let me download the latest model "eigen-6c"
106 Franz Barthelmes
Wednesday, November 02. 2011 09:11:49 UTC
Dear Sreejith, yes, it is a good idea to use the gentlecut option to avoid oscillations due to sharp truncation. But, the lower limit for "start_gentlecut" is 8. The (internal) reason for that is the subtraction of the normal potential in terms of spherical harmonics up to degree 8. In my opinion it make no sense to start with "gentlecut" lower than 8. If you really want to damp also the very low degrees you can use the option of the Gaussian filtering, e.g. with flength_definition = halfresponse" and filterlength_degree = 10. Kind regards Franz
105 sreejith
Wednesday, November 02. 2011 05:48:15 UTC
Hi, I am trying to use ICGEM calculation service to generate EGM2008 filed tuncated at n=12. To avoid oscillations due to sharp truncation at n=12, I want to roll of coeficients between n=2 and 25. When I use truncation option with start gentlecut = 2 and max_usd_degree=25, i get the out put showing trucation starting at n=8. Can anybody help to solve this issue. with best regards sreejith
104 Franz Barthelmes
Monday, September 19. 2011 06:39:53 UTC
Dear Lester, thank you for using our service and thank you for the suggestion. Although I understand your wish to have the GOCE gradient data on our service too, I must disappoint you. We are the centre for global Earth MODELS, thus we offer gravity field MODELS (up to now only in form of spherical harmonic coefficients) and not the DATA which were used to derive the models. We have the models (spherical harmonic coefficients) which have been derived on the basis of the new GOCE measurements and you can use our calculation service to calculate different gravity field functionals from these models. But regrettably the calculation of all second derivatives of the potential (the full tensor) are not included in our software. We continuously improve our software but the tensor of the second derivatives are not on the "to do list" for the next future. The reason is that we think this is something very specific and only few users would need our service for it. Kind regards Franz Barthelmes
103 Lester Anderson
Thursday, September 15. 2011 06:54:50 UTC
Hello, I have a suggestion that would be useful to many. Would it be possible to include in the table of models and calculation service, the GOCE gradient data for all the tensors? So we could then get Gzz, Gxx, Gyy, Gxz, Gyz, Gxy with the results in Eotvos. I know that the raw data is available through ESA but it is not convenient or user friendly. ICGEM already has the gravity data for GOCE so it seems logical to include the gradients too. The calculation service does allow the computation of Gzz as the second derivative of the potential (I believe that is the correct function). I would be interested in your response. Regards Lester Anderson B.Sc M.Sc DIC
102 Wolfgang Köhler
Tuesday, March 15. 2011 09:26:09 UTC
Dear Mr. Ashraf, I will answer you per email. But since this is a common cause of problems, here also again. I cite from the bottom of our HTML-page "Calculation Service": If all applets on this service are not working at all, the problem might be your local firewall. Some newer, very restrictive, firewalls block also outgoing connections. The applets need to contact the server icgem.gfz-potsdam.de, on port 1891 to query data. Please contact your network administrator to allow this connection for you. As described there, I assume, that your local firewall blocks the connection to our server. You have to open that port, to enable it. Kind regards W. Köhler, administrator
101 ashrafrateb
Tuesday, March 15. 2011 08:26:15 UTC
Dear dr Wolfgang My Greetings iam Ashraf rateb from NARSS,Cairo , Egypt My research is to study the african-arabian plate boundaris based on Gravitational model (EGM2008) I want to inquery about the funcationals of the gravitational model but there are some errors. it take me this masseage no connection to ICGEM - server at port 1891 what this meaning? and how to solve it all regards ashraf
100 Franz Barthelmes
Monday, February 14. 2011 16:30:26 UTC
Dear FALAYI OLUSEYE SEINDE, thank you for using our Service. Unfortunately I do not understand your request. I will contact you by e-mail. Kind regards Franz Barthelmes
Thursday, February 03. 2011 18:25:51 UTC
My names are FALAYI OLUSEYE SEINDE, I live in Nigeria Africa and i’m 24, I’m a fresh graduate of Physics with option in Geophysics and presently I’m serving in one of the state in Nigeria and I will be through with the National Youth Services in October 2011. Sir I did my project on the Recovery of Earth Gravity Field using Grace. Grace is a cycle satellite mission where the inter-satellite range, range-rate and range acceleration are derivable from a K-band microwave device , but the monthly data collected was not explanatory to me and I wish to acquire more knowledge on the work especially in the variation in availability of underground water in Africa. I am anticipating for positive response. Thank you sir God bless you
98 Franz Barthelmes
Tuesday, January 25. 2011 11:08:42 UTC
Dear Maria, the default values in the input mask of the calculation service are longlimit_west = 0 and longlimit_east = 360. Do you see something else? the positive direction of the longitudes is eastwards. The keywords "longlimit_west" and "longlimit_east" of the input mask of the calculation service means the following: The value for "longlimit_west" must be smaller than (or equal to) the value for "longlimit_east". The longitudes can range from 0° to 360° (0 to 2*pi) or from -180° to +180° (-pi to+pi), i.e. negative values are also allowed. If both values are negative, 360° will be added for internal reasons. Here are some examples: longlimit_west = -180° longlimit_east = +180° produce a global grid as well as longlimit_west = 0° longlimit_east = 360° but in both cases the longitudes 0° = 360° or -180° = +180° are twice in the calculated grid (which is not necessary for plotting but it doesn't matter). For gridstep = 2° a global grid can be calculated with: longlimit_west = 2° longlimit_east = 360° For regional grids all combinations are possible as long as longlimit_west < longlimit_east: e.g. longlimit_west = 13.123° longlimit_east = 27.456° longlimit_west = -80° longlimit_east = -60° will internally be changed to 280° to 300° in the grid file. Is this the answer to your question? Kind regards Franz
97 Maria Alejandra Saume
Sunday, January 23. 2011 21:40:18 UTC
Good afternoon, I am wondering about the coordinate system. I really dont understand how longitude is changing, because the page said that the eastern longitude is 0 and the western is 360, and I see this in the other way. I need to answer this question because I need to explain the input data for my thesis. I appreciate your help Maria Saume Caracas, Venezuela
96 Franz Barthelmes
Tuesday, September 28. 2010 08:01:51 UTC
Dear Leyla, I will answer per e-mail. Kind regards Franz
95 Leyla Sugaipova
Tuesday, September 28. 2010 06:03:16 UTC
Hello! Many thanks for your useful service, indeed. I have a question: In section "Evaluation of the models: Spectral Comparison with the Model EIGEN-51C" you give figures showing "... the signal amplitudes per degree of the model and of EIGEN-51C, the amplitudes of the difference to EIGEN-51C per degree and as a function of maximum degree". Could you, please, explain the last part "... as a function of maximum degree". What maximum degree is meant here? Thank you very much
94 Victor Zlotnicki
Sunday, August 29. 2010 22:30:29 UTC
You provide an extremely useful service.
93 Franz Barthelmes
Wednesday, July 21. 2010 14:01:33 UTC
Answer to all questions concerning the GOCE-models: =================================================== Yes, we will include all published GOCE-models into our service. We have the first 3 GOCE models presented at the ESA Living Planet Symposium 2010, Bergen, June 27 - July 2, 2010, Bergen, Norway. Our ICGEM-pages are prepared. But up to now ESA didn't officially released these models, so we have to wait. Kind regards Franz Barthelmes
92 Nils
Wednesday, July 21. 2010 12:11:53 UTC
Moin! Vielen Dank für den Service, der mich bisher fast jeden Tag zuverlässig mit Daten und auch Fragen versorgt. :) Eine simple Frage habe ich noch: Werden in nächster Zeit auch die GOCE Schweremodelle eingebunden? viele Grüße aus Kiel Nils
91 Franz Barthelmes
Wednesday, July 14. 2010 11:39:30 UTC
Dear Moamen Awed Habib, you can use our calculation service (button "Calculation Service") to calculate different functionals from global Earth gravity field models. A short description of the available functionals are on the calculation service site. A more detailed description is under "Theory". The model with the highest spatial resolution is EGM2008 but we don't know which terrestrial gravity measurements from the area of your interest (Egypt) are in the model. Kind regards Franz Barthelmes
90 Moamen awed habib
Wednesday, July 14. 2010 10:51:53 UTC
I would like to introduce my salf My names :moamen awed habib Country: Egypt Mob :0020115404736 Add: 1st gala rezek elmaleka faysal giza Egypt I am post guarded and I prepare research about evaluation of three newly geopotential model for my country Egypt and if you can i need gravity anomaly based on terrestrial observation and undulation based on ellipsoidal height and orthometric height data With my best regard
89 Bhupendra Thakor
Tuesday, July 06. 2010 03:29:13 UTC
Hi, Good Knowledge provider for the people who really dedicated thinking for gravity , & As i think this would be only the solution for the next generation for clean energy and innovation.
88 W. Koehler
Monday, May 24. 2010 16:33:32 UTC
Dear Mr. Clauser, I prefer to answer your question in English, because it might be of interest for other readers. At first, thank you very much for your commendation of our website! Your remark that some links on our table of models are dead, has two aspects: these links are usually given by the producers of the models and thus not under our control. When they are changed, we are in general not informed. On the other hand, the special models "eigen-xx" you mentioned are models of GFZ, and we are responsable for them ourselves ;-( We will update them asap. Kind regards W. Koehler
87 Christoph Clauser
Monday, May 24. 2010 13:15:52 UTC
Vielen Dank für die außerordentlich nützliche Seite! Eine Fehlfunktion trat auf: Wenn ich im "Table of Models" auf die Namen klickte (z. B. eigen-5c) gab es eine Fehlermedlung vom GFZ-Server, der die verlinkte Seite nicht fand. Freundliche Pfingstgrüße! C. Clauser
86 Hajo
Saturday, May 08. 2010 14:01:49 UTC
Hallo Kollegen, ... das ist einfach eine tolle Seite mit so vielen guten didaktischen Hinweisen und numerischen Möglichkeiten! Der "Besuch" gehört zum regelmäßigen Programm meiner Übungen und ist für viele BSc/MSc/Dipl.-Arbeiten unersetzlich! Vielen Dank - wie früher schon einmal mitgeteilt, Hajo Götze
85 Franz Barthelmes
Thursday, April 29. 2010 13:20:29 UTC
Dear Varuna, sorry, I fear I can't really answer your 4 questions. Question (1): There are similar questions (with answers) in the guest book. The model EGM2008 is (up to now) the only model with a resolution of degree and order 2190 and with terrestrial data which are not available for others. The real resolution of the model in an area of interest (e.g. India) depends on the data which have been used from this region to establish the model. We are not the authors of EGM2008. I good idea to get an impression of the resolution of a model in an area of interest is to generate a plot of this area using our calculation service. Question (2): Please ask an expert in this field :-) . Question (3): Use the internet for searching and study the literatur (sorry :-)) Question (4): The improvement is very easy ;-) If you want to improve a global gravity field model for a specific area you must have gravity field data relevant for this area which are not yet in the model. Then use one of the well-known mathematical methods (techniques, algorithms) to calculate an improved model. Kind regards Franz
Tuesday, April 27. 2010 07:04:03 UTC
Dear Sir, For Indian region, which model is best suitable? Regarding gravity measurements, using relative gravimeter CG-3 , is it necessary to close the loop every day for computation of drift? References / Software for development of a regional Geopotential model or Global Geopotential model? How to improve the accuracy of EGM96 or EGM2008 for the Indian region? With regards, Varun
83 W. Koehler
Monday, March 22. 2010 08:54:20 UTC
Dear Rajesh, please use the button "Calculation Service" on the left side. Kind regards.
82 Rajesh Kumar
Monday, March 22. 2010 06:26:33 UTC
I wanted to use "Service for Computing Data from Models" under software but unfortunatitly i am unable to find that option . how can i use this service? Appreciated if you reply soon.Thanking you.
81 Bill Oberg
Thursday, February 18. 2010 16:46:31 UTC
I am working on a project with other scientists that hopefully will predict earthquakes using Iasobergs. I will try to integrate these images with my study. Thank you. Bill Oberg
80 Victor Glaznev
Saturday, February 13. 2010 07:24:47 UTC
Fine! I often use yours Calculation and Visualization Service for education and science purposes. Million thanks for authors!
79 Hunja Waithaka
Thursday, February 11. 2010 04:06:20 UTC
This is quite a resourceful site. Keep up the good work.
78 Franz Barthelmes
Tuesday, January 26. 2010 14:41:33 UTC
Please address questions about the accuracy of the models to the authors of the models. Kind regards Franz
77 Ghadi Younis
Monday, January 18. 2010 07:29:59 UTC
Dear Franz, thanks for clearing the confusion, I think a description of the height system (ellipsoidal or Orthometric) can solve the confusion in the future. other question: what is the accuracy of gravity data from EIGEN04c EIGEN05c and EGM2008? best regards, Ghadi Younis
76 Franz Barthelmes
Friday, January 15. 2010 13:21:42 UTC
*** The height coordinate *** Hello Everyone, the question of Ghadi Younis showed me that my item from 15. August 2009 in "Latest Changes" was not correct. For the functionals: - gravity_disturbance - gravity_anomaly - gravity_earth - height_anomaly a column with the height coordinate of the point where the functional are calculated were added. This height coordinate is not the ellipsoidal height as stated. It is the bi-linear interpolation of the digital terrain model which is the height above sea level (i.e. above the geoid). The calculations are (and were) correct. During the calculation from spherical harmonic models the positions have to be transformed into ellipsoidal height coordinates (and then into spherical coordinates) and for that the geoidal heights are added. But the output is (and was) the unchanged bi-linear interpolation of the digital terrain model (and I think it is the more useful information). ==> So the mistake was only the description. *** Sorry for the confusion. *** Kind regards Franz
75 abdullah susanto
Thursday, January 14. 2010 04:31:16 UTC
my name abdullah susanto I'm student S1 in Geodesy-ITS Surabaya, Indonesia
74 Franz Barthelmes
Friday, January 08. 2010 11:07:04 UTC
Dear Ghadi Younis, I was a little incorrect in my last answer. I said: "The grid coordinates are always ellipsoidal coordinates." and "The topography of the Earth's surface is calculated by bilinear interpolation of the etopo2v2-grid." --> This is correct. But: The heights of etopo2v2 refer to sea level and not to the ellipsoid (as far as I know ;-) ). Therefore, in the program geoid heights are added to the interpolated etopo2-heights to get the height coordinates of the Earth's surface with respect to the ellipsoid. Kind regards Franz
73 Franz Barthelmes
Wednesday, January 06. 2010 16:53:53 UTC
Dear Ghadi Younis, the grid coordinates are always ellipsoidal coordinates. The topography of the Earth's surface is calculated by bilinear interpolation of the etopo2v2-grid. The heights there are ellipsoidal heights (as far as I know). Kind regards Franz
72 Zakarneh
Wednesday, January 06. 2010 11:42:51 UTC
Dear Franz. I need to have deflections of Vertical sincerely yours, Zakarneh
71 Ghadi Younis
Wednesday, January 06. 2010 11:40:09 UTC
Dear Franz, thanks for your answer. when I calculate gravity_earth .. is the given height in the output file Orhomrtic or ellipsoidal height? because differeces ib BadenWürttemberg are +-50 meter. I am working in local Gravity and Geoid modelling .. in TU-Darmstadt and HS-Karlsruhe. I get additional observations to direct observations from. DFHBF(www.dfhbf.de),EGG97 , egm2008 and Eigen-05c models. all provide deflections of vertical. except eigen-model using Calculation service. Regards, Ghadi Younis
70 Franz Barthelmes
Tuesday, January 05. 2010 13:58:32 UTC
Dear Ghadi Younis, yes, you are right, the calculation of grids of deflections of the vertical would be useful. We are working on that - it is a question of priorities :-). Is there anybody else who need it? ;-) Kind regards Franz
69 Slim Pickens
Monday, January 04. 2010 18:41:54 UTC
Thanks for this site!
68 Ghadi Younis
Monday, January 04. 2010 17:38:43 UTC
Hallo , it would be nice if the caculation service can also calculate deflections of vertical in the given grid.. added to geoid or heights anomalies grid or seperstely in a seperate grid computation
67 Franz Barthelmes
Friday, November 20. 2009 09:41:29 UTC
Dear Henry Codallo, there are functionals of the Geopotential which are defined in space (as e.g. the potential itself or the second r-derivative) and there are functionals which are defined only as 2-d functions depending on longitude and latitude (as e.g. the geoid or the classical gravity anomaly). For the latter it makes no sense to ask to which surface it refers. Look at the table on the calculation site or the report available under "Theory of the Calculation Service" to see how the functionals are defined. Take it as an exercise course to find out what kind of functional the Bouguer anomaly is :-) . Kind regards Franz
66 henry codallo
Thursday, November 19. 2009 11:29:27 UTC
Ok I Know, but if i want a grid of anomaly bouger , this grid will be referenced to the ellipsoid and not to the geoid?? or it doesnt matter?? (height ellipsoid value 0) thanks henry codallo
65 Franz Barthelmes
Wednesday, November 18. 2009 10:10:52 UTC
Dear Henry Codallo, "height over ellipsoid" means: height over the ellipsoid of the used reference system (e.g. wgs84), measured along the direction of the normal gravity vector (along the ellipsoidal normal). If you use h=0 (which is not possible for all functionals) the functional is calculated on the ellipsoid. You can find more about that in the report: http://icgem.gfz-potsdam.de/ICGEM/theory/str-0902.pdf Kind regards Franz
64 henry codallo
Tuesday, November 17. 2009 21:51:32 UTC
hello friends, what the height over ellip means??? what happen if i let the default value 0 when i'm computing a grid for example for all venezuela??? thanks best regards henry codallo
63 David Philip
Sunday, October 25. 2009 12:01:05 UTC
Superb is my first impression. The graphics and the explanations are excellent. I hope to learn a lot. Best regards David Philip
62 Franz Barthelmes
Friday, October 02. 2009 10:57:05 UTC
Dear Johnny, the short answer is: The grids are calculated without any interpolation. Why do you think there could be interpolation? With the coefficients of the model, together with the spherical harmonic functions, we can calculate the functionals at any arbitrary point in space. The functionals are calculated exactly at the gridpoints of your choice without any interpolation. The calculation (estimation, approximation) of the coefficients is another problem. Kind regards Franz
61 Johnny Merchan
Thursday, October 01. 2009 15:49:12 UTC
Greetings, I'm Johnny Merchan - Venezuela Another question, taking into account the issue of spherical harmonics. In the Calculation Service exist interpolation?. What is that interpolation?. For example Krigging, bilinear, minimum curvature, Natural neighbor, etc. Again, thank you
60 Franz Barthelmes
Monday, September 28. 2009 14:31:42 UTC
Dear Johnny Merchan, the generation of a global gravity field model in spherical harmonic coefficients is much more complicated than simply converting an equidistant grid into spherical harmonics. Usually the computation of the spherical harmonic coefficients of a so-called combined model (there are also "satellite-only models") is a sophisticated combination of gravity field information from satellites, from altimetry over the oceans, from irregularly distributed terrestrial measurements and a lot of additional information about the atmosphere, the ocean etc. The maximum degree and order of the mathematical representation of EGM2008 in spherical harmonics is 2190. That means formally (mathematically) the resolution can not be better then about 10km half-wavelength (hills or dales). The real resolution of the model in an area of interest (e.g. Venezuela :-)) depends on the data which have been used from this region to establish the model. We are not the authors of EGM2008. I good idea to get an impression of the resolution of a model in an area of interest is to generate a plot of this area using our calculation service. Kind regards Franz Barthelmes
59 Johnny Merchan
Thursday, September 24. 2009 17:14:45 UTC
Greetings, I'm Johnny Merchan It's great Calculation Services of ICGEM. I am currently using the Earth Gravity Model 2008 to a gridstep of 0.5 degrees for Venezuela. I ask. What is the Earth Gravity Model 2008 gridstep without interpolation?. Originally, what is the spacing of the data Earth Gravity Model 2008 without interpolation? ó know what the sampling rate model of the data Earth Gravity Model 2008?. Thank you very much Caracas - Venezuela
58 Nadezhda Konanova
Wednesday, July 22. 2009 09:06:48 UTC
your posting
57 W. Koehler
Monday, June 22. 2009 08:01:30 UTC
Dear Rogers, you are right, this possibilty was broken due to an implementation mistake. Now it is possible again, to compute one point and one line of points. kind regards wolfk
56 rogers
Friday, June 19. 2009 13:49:08 UTC
Isn't it more possible to calculate information about only one point? Before it was possible utilizing the same point in the grid... Thanks. Rogers
55 Wolfgang Köhler
Friday, June 12. 2009 19:10:00 UTC
Dear Paolo, sorry, I have checked my logfiles and see that you are right. The problem is, that I had to install a safety-check today, that prevents the server from massive parallel usage by some users. This check obviously failed in your case. I have to see what exactly is going wrong there, but this will have to wait until Monday. Sorry for the trouble. wolfk
54 Fernando Paolo
Friday, June 12. 2009 16:00:54 UTC
Please, what is going on??? I have waited for the calculation service, and now all the time I try to perform some calculation I receive the message: * sorry, you have already 3 processes running at the moment...* I DO NOT HAVE ANY PROCESS RUNNING! 3 process? I could not started even one. Fernando Paolo University of Sao Paulo.
53 Liang Fang
Friday, June 05. 2009 14:52:53 UTC
I want to use this model to do some test.
52 Liang Fang
Friday, June 05. 2009 14:50:02 UTC
your posting
51 Franz Barthelmes
Thursday, May 28. 2009 10:08:42 UTC
Dear Carolina, the topography in spherical harmonics (model DTM2006) is used to calculate the geoid undulations from pseudo height anomalies considering the topographical effect (spherical shell approximation) for the functionals: geoid gravity_anomaly_cl and additionally a digital terrain model is used (bi-linear interpolation of the ETOPO2v2-grid) to calculate the exact height on the Earth's surface (geoid + topography) for the functionals: height_anomaly gravity_disturbance gravity_anomaly gravity The zero degree term is a constant offset due to a possible difference between the GM-values of the model and the reference system (normal potential). Kind regards Franz Barthelmes
50 Carolina
Wednesday, May 27. 2009 21:25:31 UTC
your posting I want to know to calculate disturbance whether the calculation includes a digital terrain model and what is the diferncia of calular or not the term of order zero thank you very much
49 Victor Zlotnicki
Thursday, May 14. 2009 05:52:43 UTC
Extremely useful. Although I have the spherical harmonic reconstruction code, and I use it routinely to convert GRACE to water equivalent, the evaluation of various functionals, with various Tide systems and with various smoothing radii, done so quickly, is extremely valuable and saves me a lot of time. Thank you very much! Victor
48 Franz Barthelmes
Monday, May 11. 2009 12:12:38 UTC
Dear Rogers, can you formulate your question more precisely, please? In our Calculation Service we offer the calculation of Molodensky-gravity anomalies, classical gravity anomalies and the spherical approximation. For more information please look at the short description on the site "Calculation Service" or at "Theory of the Calculation Service". Kind regards Franz Barthelmes
47 rogers
Friday, May 08. 2009 17:53:36 UTC
How to reduce gravity anomalies from ellipsoid to surface of earth?
46 Franz Barthelmes
Monday, April 20. 2009 10:17:43 UTC
Dear Alexandre B. Lopes, it is nice to hear that our service is useful. If you have any questions don't hesitate to contact me (e-mail: bar@gfz-potsdam.de). We are always interested to know how the service could be improved. So if you have critics or suggestions for improvement - let us know. Kind regards Franz Barthelmes
45 Alexandre B. Lopes
Monday, April 13. 2009 22:23:18 UTC
The service is very good. I use to calculate and to compare geoid models. I work with ocean dynamics topography (MSS-N) and geostrophic circulation. I use follows geoidal models: 1 - EIGEN-5C; 2 - EGM2008. thanks
44 Franz Barthelmes
Tuesday, April 07. 2009 11:34:25 UTC
Dear Francisco Palominos, on the web pages of our service you can also find the model references (button "model references") and a link to the original site of the model (if available). I will send you information about the eigen-1 model per e-mail. Kind regards Franz Barthelmes
43 Francisco Palominos
Tuesday, April 07. 2009 00:26:54 UTC
Hello my name is Francisco Palominos , I am a student of Engineer Geomátic of the University of Concepción Chile, and I need information about geoidal models in especial EGM96, EGM2008, and eigen 1. can you answer me in Spanish please? If you do not can , no matter thank you...
42 Alpay ABBAK
Sunday, March 01. 2009 14:20:07 UTC
Dear colleage, 'E' symbol is not written in degree 2 order 0 of GGM03s coefficients. Best regards...
41 Franz Barthelmes
Friday, January 09. 2009 08:34:39 UTC
Dear Alpay ABBAK, the spectral behaviour of each model is shown on our service (button "evaluation of models"). How the curves of signal amplitudes per degree look like depend on how the models have been calculated (input-data, mathematical method of approximation, stabilisation method etc.). I don't understand the question: "What rule checks the signal amplitude of the model, absolutely?" May be your question is: "What is the rule of thumb of the signal amplitudes per degree of the REAL gravity field of the Earth?" Kind regards Franz Barthelmes (ICGEM-Team)
40 Alpay ABBAK
Sunday, December 28. 2008 13:34:56 UTC
dear colleague, I wonder what is the rule of thumb in signal amplitudes per degree of any model? Namely, What rule checks the signal amplitude of the model, absolutely? thanks for your interest.
39 Franz Barthelmes
Tuesday, December 02. 2008 12:55:47 UTC
Dear Olalekan Isioye, yes we want to improve our service step by step and we are greateful for all proposals. Unfortunately I don't understand what you mean with: "...that users can download specifically what they want from little information that can be provided by users" So please be so kind and tell us what you would like to download? Kind regards Franz Barthelmes (ICGEM-Team)
38 olalekan ISIOYE
Monday, December 01. 2008 10:37:39 UTC
Your calculation service should be inprove on. such that users can download specifically what they want from little information that can be provided by users
37 wolfk
Friday, November 14. 2008 10:24:59 UTC
36 Franz Barthelmes
Thursday, October 30. 2008 09:44:50 UTC
Dear Robert Onslow, thank you for using our Service and thank you for calling our attention to the mistake. Uo to now nobody has noticed it because missing coefficients usually will assumed to be zero by the software. After talking to the authors of GGM03s it has been corrected on our service. Kind regards Franz Barthelmes
35 Robert Onslow
Wednesday, October 29. 2008 14:55:56 UTC
Also, GGM03 l=1 m = 1 is missing Robert
34 Robert Onslow
Wednesday, October 29. 2008 14:48:36 UTC
Is the ICGEM version of the GGM03 model correct? Please see l=180, m = 179 and l = 180, m = 180. Robert
33 Franz Barthelmes
Tuesday, October 14. 2008 14:21:50 UTC
Dear William Rose, thank you for using our service. The calculated (predicted) gravity relates to the Earth's surface calculated by the geoid from the gravity field model plus the topography model. The topography model is necessary for two different purposes: (a) to calculate the geoid undulations from height anomalies by adding a topography dependent correction term, and (b) to calculate the exact coordinates on the Earth's surface (if needed for the functional - e.g. gravity). For (a) a spherical harmonic expansion of the topography is used with the same resolution (maxed_used_degree) as the used gravity field model, and for (b) we use bi-linear interpolation of the original ETOPO2-grid to calculate the elevation of position as accurate as possible. If you specify the functional "topography" our service calculates the topography from the spherical harmonics. Unfortunately up to now the grid interpolation of the topography is not provided as output, we will think about offering it too. Some hints: I would use the new high resolution gravity field model EGM2008. The coordinates should be as accurate as possible. For Johannesburg I get with EGM2008: for lat: -26.2 long: 28.08333 => elevation from shm: 1538.4 m => elevation from grid: 1712.5 m => gravity: 978545.95868 mgal for lat: -26 long: 28 => elevation from shm: 1669.9 m => elevation from grid: 1402.99 m => gravity: 978586.956722 mgal If you have better values for the elevation it is a good idea to use the gravity gradient for correction. A general question is: how accurate do you need the gravity at the point of interest? I hope this helps a little, if you have further questions please contact me at bar@gfz-potsdam.de Kind regards Franz Barthelmes
32 William Rose
Monday, October 13. 2008 18:03:07 UTC
I'm not a geologist. I'd like to know the gravity in Phildelphia, USA and Johannesburg, SA for purposes of calibrating an accelerometer. I have entered the lat & long of each location in your calculator to get two "grids" with one point each. I specify "gravity" as the functional to be computed. Is the gravity which is then computed the predicted gravity for "sea level" at that lat & long? If so, I will subtract 0.197 mGal/m*actual city elevation, to adjust for elevation of each city. Or does the software report the gravity at the "predicted elevation" for that location (the elevation reported when I specify "topography" as the output)? In that case, the elevation correction will be smaller. For example, "topography" reports an elevation of 1450 m for Jo'burg's lat & long, so I would subtract 300m*0.197 mGal/m, since Jo'burg is at 1750 m, 300 m higher than the "topography" mdoel. Thank you.
31 'Franz Barthelmes
Thursday, September 04. 2008 14:02:21 UTC
Dear Sekhar, the formal resolution of a model in spherical harmonics depends on the highest degree and order of the development. The real resolution in the area of your interest depends on the data, which are included in (approximated by) the model. We are not the authors of the model EGM2008. Our "table of available models" have links to the original sites of the models. For EGM2008 it is: http://earth-info.nima.mil/GandG/wgs84/gravitymod/egm2008/index.html Kind regards, Franz Barthelmes
30 'Sekhar'
Thursday, September 04. 2008 02:20:59 UTC
Dear sir, what is the accuracy of EGM-2008 model in case of land. If i want to utilise this data, what could be minimum area, minimum grid interval i can select, if i do it through your calculation service. My interest was analysis of geoid at different degrees over extent of 5degreex 5 degree for geodynamic studies related to himalayas. Can u suggest any literature related to this. sekhar
29 Ahmad
Tuesday, August 05. 2008 17:37:59 UTC
it will make more sence if you show the COMMENTS in the HTML page not into a Text Area.
28 Ahmad
Tuesday, August 05. 2008 17:36:24 UTC
Nice guest book :)
27 Franz Barthelmes
Monday, June 30. 2008 11:45:41 UTC
Dear Terepaima Tabare, I tried to write you an e-mail to "terepaimatabare@gmail.com" but it failed. So please write me an e-mail to "bar@gfz-potsdam.de". Kind regards Franz Barthelmes
26 Terepaima Tabare
Thursday, June 26. 2008 15:18:44 UTC
My e- mail is terepaimatabare@gmail.com , thak you for helpme and your service is very good, and the grids is of great utility for gravity maps of my country.
25 Terepaima Tabare
Thursday, June 26. 2008 15:09:05 UTC
Hello I am the engineer Terepaima Tabare, I write to request information about training courses and training in the use, handling in applications of satellite data derived from satellites and Grace CHAMP. I write from the agency Bolivarian for space activities in which Venezuela institution work. As an institution we are interested in training in this area. Where you can find such courses?; if there is no possibility that there is a design according to our needs?. Thank you very much Caracas- Venezuela
24 Franz Barthelmes
Tuesday, May 20. 2008 16:41:36 UTC
Dear Rajasekhar, I guess with "at different harmonics" you mean the band-pass filtering of the geoid by calculating geoid-grids using only the coefficients of a "band" of degrees l: lmin < l < lmax. You can do this by using our calculation service to generate grids with different values for "max_used_degree" and computing the grid-differences as a second step by yourself. If you have further questions, do not hesitate to contact me at "bar@gfz-potsdam.de". Kind regards, Franz Barthelmes
23 Rajasekhar
Tuesday, May 20. 2008 14:00:39 UTC
Dear sir, i want to analyse the geoid at differnet harmonics from recently available models EGM2008; EIGEN-GL04C. This will helpful to study geoid at different wavelengths. Can u suggest is there any program or software to do this exercise. Rajasekhar
22 Franz Barthelmes
Friday, May 16. 2008 08:55:09 UTC
Dear Ariel Silva Hidalgo, thank you for using our service. Unfortunately in our ICGEM-Team nobody speaks spanish. I guess you ask for a manual in spanish? - No, all things are in english (as usual in science ;-)). Kind regards, Franz Barthelmes. My e-mail is: bar@gfz-potsdam.de
21 Ariel Silva Hidalgo
Thursday, May 15. 2008 20:51:43 UTC
Gracias por realizar sitios como éste. Felicitaciones por el trabajo realizado, me ha sido de extrema utilidad. ¿Publicarán algún manual en español?
20 Franz Barthelmes
Monday, April 14. 2008 10:57:06 UTC
Dear Terepaima Tabare, on our site "calculation service" is an explanation, what the functionals are. For example: "The gravity anomaly (according to Molodensky's theory) is defined as the magnitude of the gradient of the potential on the Earth's surface minus the magnitude of the gradient of the normal potential on the Telluroid (Earth's surface minus height anomaly). Here it will be calculated as exact as possible." I think this is non-ambiguous. To help you, please tell me what you don'nt understand. Best regards Franz Barthelmes. My e-mail is bar@gfz-potsdam.de
19 terepaima
Friday, April 11. 2008 20:23:48 UTC
HI, I an Ing. Terepaima Tabare from Venezuela. I am a bit new to this, I like know information of gravity product that your seriously.. I would like to clarify that which anomaly you offer in the calculation service?? air free anomaly or Bouguer anomaly? and I like to read abaut the kind of corrections applied to the data for example in the model EIGEN-GL04C. I want to Modeling gravimetric with this type of satellite data!! Thank you..
18 Alpay ABBAK
Friday, February 01. 2008 08:42:02 UTC
Hi, I am PhD student of Turkey. I would like to know if there is any paper about evaluation of models and methods in your site. Thanks... my e-mail: aabbak@selcuk.edu.tr
17 Franz Barthelmes
Wednesday, November 14. 2007 10:14:35 UTC
Dear Maria Eugenia, a short description what the functionals are is on the calculation service site. A poster with the formulas can be downloaded from: ftp://ftp.gfz-potsdam.de/pub/home/sf/bar/publications/Poster-ICGEM-Formulas.pdf A description of the theory behind the calculation service is in preparation. If you have more detailed questions please contact me on bar@gfz-potsdam.de (I don't know your e-mail address).
16 Maria Eugenia
Wednesday, November 07. 2007 16:33:02 UTC
Hi, I am a PhD student of Argentina. I would like to know if there is any paper with the explanation of the formulation involved in your calculator, as exist for EGM96. Thanks
15 rodrigo abarca del rio
Thursday, December 28. 2006 11:29:21 UTC
HiThe Evaulation service is not working, nor the software download service.regards rodrigo abarca del rio dgeo universidad de concepcion chile
14 Steve Kaye
Wednesday, November 15. 2006 10:35:20 UTC
This is a first-class site and data - excellent service. Thank you.A little feed-back. I'm using EIGEN-GL04C, in combination with Scripps Institute satellite derived gravity and my own data from some islands, to produce Bouguer anomaly regional and residual images and maps for the Banda Arc area in Indonesia. Using your data removes (partially) the subjectivity typically present in the old 'classical' methods for producing regionals and residuals. The results are very promising and I look forward to extending the work over land masses once the 'geoid-height' function is available. You can see soem of this work at http://www.stevekaye.nadsl.net/regional_and_residual_gravity.htm - be careful, large images!
13 phani
Friday, July 28. 2006 04:49:09 UTC
I am PhD student at National Geophysical Research institute, India. Iam interested work with satellite gravity data as a part of my PhD work. Iam interested in analysis of satellite gravity anomalies and geoid over India and anomalies. Recently i seen a paper in Gondawana Research by Choi at al.,, they analysed Grace data over north eastern China and korean peninsula. They used GRACE-CHAMP gravity data of 130,317 spherical harmonic coeffiecints to degree and order 360. Iam also interested in same kind of qualitative work over India, which is part of my PhD work. for this how can i extract from the site http://icgem.gfz-potsdam.de/ICGEM/ICGEM.html.Iam confused to provide min_degree used, max_degree used and orders only_start, orders _only end, start gentle cut. Can u suggest in this regard to over come this problem. Can u suggest any literature related to these parameters.
12 jenny
Friday, June 23. 2006 04:15:05 UTC
I enjoyed staying with your site, will surely come back to learn more.
11 Franz Barthelmes
Tuesday, June 06. 2006 14:27:23 UTC
Hi hluzo, tide system transformation is basically a C20 change.For further details contact me: bar@gfz-potsdam.de
10 hluzo
Friday, June 02. 2006 13:39:04 UTC
Great idea to have ICGEM.I have also questions about tide systems. How can I transform the global gravity model from one tide system to another? Is it only C20 transformation? Does it exist a universal formula for tide system transformation?
9 David Sandwell
Friday, May 05. 2006 17:13:08 UTC
This is a nice service. I'm computing height anomaly and gravity anomaly for EIGEN04.
8 chris
Sunday, April 16. 2006 19:34:12 UTC
can i get this applet?
7 wolfk
Monday, February 13. 2006 23:00:00 UTC
Of course, you can use this applet, if you keep the copyright notice. However, please note that it needs data transfer from the server.
6 Alex
Monday, February 13. 2006 09:58:02 UTC
Can i use this applet or does it have copyright etc?
5 Franz Barthelmes
Thursday, December 08. 2005 16:32:52 UTC
Answer to the question by Peter Löwe concerning the computation of geoid undulations: Up to now we offer the possibility to calculate the height anomaly on the ellipsoid, which is often called the "pseudo height anomaly". To calculate the geoid from the pseudo height anomaly it is necessary to know the density distribution of all topographical masses above the geoid. A simple approximation is to consider the influence of an equivalent Bouguer plate. This is what we plan to offer soon. Don't overestimate the accuracy of this approximation and note that the spherical harmonic models up to degree and order 360 (e.g. eigen-cg03c) do not contain structures (bumps) smaller then ca. 50km.
4 Peter Löwe
Thursday, December 08. 2005 09:41:07 UTC
when will it be possible to use the "Service for Computing Data from Models" for computation of geoid undulations referred to EIGEN-CG03C ?
3 Franz Barthelmes
Tuesday, July 26. 2005 14:42:48 UTC
Answer to M. Sadiq: Thank you for your interest. You can use the software under the button "Service for Computing Data from Models". There you can calculate grids for areas of your choice. For further questions please contact me: bar@gfz-potsdam.de Kind regardsFranz
2 M Sadiq
Saturday, July 23. 2005 12:57:11 UTC
I am Ph.D. Student at Quaid-i-Azam University Islamabad, Pakistan. My topic of study is Gravitational geopotential modeling. I need the Gravity field parameters of EIGEN CG03C gravity model e.g. Height anomaly, Gravity anomaly and Geoid Undulations etc. Is there any software to calculate these parameters of the model. Could it be provided to me for research purpose. I need data for the whole area of Pkistan of above mentioned parameters.Kind regardsM Sadiq
1 hans
Tuesday, May 10. 2005 00:42:30 UTC
It is very nice.