Hi Martin,
Martin <martin.spel@rtech.fr> a écrit :
I am looking at how to transform an initial condition defined by (longitude,
latitude, altitude, relative velocity, flight path angle and orbit
inclination
angle), to orbital parameters that can be used by Orekit. Is
somebody already
using such transformation or can has some reference on a transformation that
can be used?
You can use a trick to achieve this result: use a TopocentricFrame.
First, set up the frame using the latitude, longitude and altitude
(using an intermediate GeodeticPoint object). You can build the
relative velocity from velocity amplitude and spherical angles
flight path and inclination in this frame, knowing that its X axis
is towards East, and Z axis towards zenith. In this frame, your
spacecraft coordinates are (0, 0, 0) for position and (vx, vy, vz)
for velocity. You just have to transform it to any other frame like
EME2000 using the standard frame transforms. Here is a rough
skeleton of this process:
GeodeticPoint gp = new GeodeticPoint(latitude, longitude, altitude);
TopocentricFrame frame = new TopocentricFrame(earth, point, "initial");
Vector3D relativeV = new Vector3D(....);
Transform t = frame.getTransformTo(FramesFactory.getEME2000(), date);
PVCoordinates pv2000 =
t.transform(new PVCoordinates(Vector3D.ZERO, relativeV));
best regards,
Luc
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