Estimate GPS satellite coordinates' at given instant

Orekit usage
1

Hi everybody, I’m trying to understand how Orekit could be used to estimate the (x,y,z) coordinates of a GPS satellites at a given instant using a YUMA file.

My knowledge is very limited at the moment, I’d like to explain what I have understood so far. Using YUMAParser I can generate a GPSAlmanac for the target satellite. Knowing the orbital parameters and when the almanac was generated I should create an Orbit instance (maybe creating a KeplerianOrbit instance) providing the right Frame instance. Using a Propagator, I can then estimate the SpacecraftState at the target instant and lastly get the coordinates I’m looking for.

Am I on the right path? Thank you very much!!

2

Hi @giulioscattolin

First, welcome to the Orekit forum!

In order to compute the satellite coordinates’ from a GPSAlmanac, you have to use a GPSPropagator. Here, an example demonstrating how to initialize the GPSPropagator:

final GPSPropagator propagator = new GPSPropagator.Builder(almanac).build();

Where almanac is the GPSAlmanac that you generated from the YUMAParser.

Kind regards,
Bryan