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The principal product of arc is the GPS satellite ephemeris. Historically called the "u_file", this is a binary file to minimize file size and time reading this file. arc is capable of generating strictly the ephemeris or, as it is more commonly used, the ephemeris with the appropriate partial derivatives for adjusting the ephemeris.
The u_file begins with a few lines of descriptive information which includes:
This is followed by the epoch-by-epoch information of the ephemeris. Each line contains all terms for all satellites. No time or descriptive information is include on these lines since all pertinent information was given in the header lines. All values on these lines are double precision and all terms for a satellite are grouped together. Remember that all information for each epoch is held on a single binary line. The FORTRAN pseudocode to read one of these lines would look something like
read( lu ) (( vector(i,j), i= 1, "terms per satellite",), j= 1, "satellites")The terms are, in this order:
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