February 2, 2006

SOFTWARE TO TRANSFORM EPHEMERIS FILES AVAILABLE

Since January 29th, 2006 the International GNSS Service (IGS) began
making its precise ephemeris files available only in the SP3-c format.  
For the time being, NGS will continue to make available the precise orbits 
in both SP3-a (files with extension *.sp3) and 
SP3-c format (files with extension *.sp3c).

If anyone needs to convert a file from SP3-c format to the older SP3-a format, 
there is a Windows NT/2000/XP executable to do this available at:

    http://www.ngs.noaa.gov/CORS/Utilities/Orbits/NT/

There is also source code written in the C computer language that people can
compile and use on other computer platforms like Linux, Unix, etc.  This
C source code is available at:

    http://www.ngs.noaa.gov/CORS/Utilities/Orbits/Source/

This sp3csp3a program requires command line arguments; it can be run in a
DOS command prompt window on a PC.  The typical usage is:
sp3csp3a.exe  input.sp3c output.sp3a