GNSS pos processado - open source ou free

Spectra Solutions GNSS

OPUS
https://www.ngs.noaa.gov/OPUS/  - processamento online

RTKLIB
http://www.rtklib.com/

GPSTk
http://www.gpstk.org/bin/view/Documentation/WebHome

GAMIT/GLOBK/TRACK
http://www-gpsg.mit.edu/~simon/gtgk/index.htm

GIPSY-OASIS II
https://gipsy-oasis.jpl.nasa.gov/