This is an interactive Java Applet to visualize the Gravity. You have many options
to load other models, change grid resolution, viewpoint, zoom, light source parameters ...
You must enable Java for your browser to use it.
Netscape 6.xx, Mozilla, MS Internet Explorer are recommended browsers.
Older versions of Netscape will work, but much slower, because they do not have installed a
If you don't see it correctly on your browser, please inform us per Email (include the used browser version and operating system).
Please have some seconds patience for loading the applet. See below the applet for usage info.
Most buttons (or the button-labels) have a help option: if you move the mouse cursor
over it, a small popup will explain its function.
The Earth can be rotated either with mouse cursor dragging (sometimes a bit slow) or the keyboard actions (see below).
Please note, that the Applet must have the focus for keyboard actions!
If you want to experiment with certain display variables (as
light, model, lmax, zoom, viewpoint, ...)
it is probably the best way, to first use a small grid-resolution (2° or 4°).
Also 'rotating' and interactive motions will work more fluently with lower resolutions. After finding out the best display, you can set the resolution to the desired value. Doubling the grid size will produce a nearly four times increased update time (and memory requirements).
To use very fine resolutions < 0.5°, you should close all other browser pages, to have the maximum available Java heap space (e.g. a grid resolution of 0.2° needs about 540 Mb memory).
If you experience some odd behaviour of your applet (no reaction to buttons, no image updating, ...) you can inspect what is going wrong, if you have a look at the Java Console of your browser. For Netscape 6.xx you open it with the buttons Tasks → Tools → Java Console. There the main actions and errors are logged and you have the possibility to control the Java Virtual Machine (JVM).
One common error, which freezes the applet is the "OutOfMemoryError". It occurs
if the pre-allocated heap memory for your JVM is exhausted, usually already in the
step "generating sphere points". This can happen for grids < 0.5°, because
some older browsers only allocate 64Mb for Java.
(You can see the error message in the Java Console window of your browser.)
You can circumvent this failure e.g for Windows-PCs, if you change the default value in the browser preferences under
"Java" → "runtime environment" →
"runtime parameter -Xmx500m" to allocate eg. 500Mb heap space.
If you see only a blue sphere in the window but no geoid, then there is a network/server problem (eg. your local firewall blocks the connection). Please inform us about this, we try to help.
The Applet is loaded from the server host "icgem.gfz-potsdam.de" with "Potato.jar".
It requires a running potato-server listening on TCP-port 1891.
After start of the applet, it queries from the server the list of available models,
which build up the model choice of the
applet. Then it serves model queries in form of grid values.
The applet needs quite a lot of memory, depending on grid-resolution. In the default resolution of 1° × 1° it occupies approximately 16 Mb, resolution and about 60 Mb for 0.5° × 0.5°.