Hi prof hwang,

Q1: can you demonstrate how to wrap a world map onto the circle(sphere) in 3D view ?
http://science.nasa.gov/Realtime/JTrack/3d/JTrack3D.html
[img]http://66.7.205.91/~lookangc/forum/index.php?action=dlattach;topic=174.0;attach=18[/img]
there is a non rotating Earth

many people can't visualize the meaning of geostationary orbit, i hope to help make an applet.

Q2: why is the xml file you declare GM = R*R instead of using the G = 6.67*10^-11 and M = 6.0x10^24 ?

the rest still thinking, those i know i post here for others to learn  ;D

Model constraint page:
cta=-Math.atan2(x,y); // cta is angle of satellite from origin which is earth comment lines by weelk
r=Math.sqrt(x*x+y*y); // r is radius of rotation comment lines by weelk
if(r>xmax*scale)scale=r*1.2/xmax; // just a way the scale the simulation 1.2 times bigger if the radius in getting bigger than xmax*scale instead of autoscale all the time comment lines by weelk

Model custom page:
double r,r2,r3,cst;
public double getA (double x, double y) {
r2=x*x+y*y;
r3=r2*Math.sqrt(r2);
return -GM*x/r3; //clever way of function getA (x,y) acceleration along each axis comment lines by weelk
}

I was hoping i can modify your codes to make a realistic earth with satellite in 3D view.

i will later add potential versus distance, mass of satellite changeable.

and others can use your template to make applets to suit their needs.  ;D

thanks