### Computing Satellite Velocity using the Broadcast Ephemeris (includes C code)

The technical paper which describes the bc_velo.c program is published inGPS Solutions, Volume 8, Number 2, 2004 (in press). "Computing Satellite Velocity using the Broadcast Ephemeris", by Benjamin W. Remondi

A set of equations has been derived which allows one to compute the velocity

vector for a GPS satellite using time derivatives of the Keplerian elements

and correction terms broadcast from the GPS satellites, as described in the

GPS Interface Control Document (ICD-GPS-200). This document is available

from the U.S. Coast Guard website at

http://www.navcen.uscg.gov/pubs/gps/icd200/default.htm.

A complete main program written in C (bc_velo.c) is included here to

illustrate how these equations can easily be incorporated into source code

to yield accurate velocity components. The reader can use this C code to

create a similar subroutine or function which will compute the position and

velocity of a satellite given the broadcast ephemeris data, the PRN name,

and a requested GPS time (transmission time) in units of GPS week and

seconds-of-week. In practice, a pointer to a broadcast structure would be

passed to a similar C function. It should be pointed out that the ambiguity

with respect to the GPS week has been ignored in this simple example

program.

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