This is a hackish port from the ode provided in A Software-Defined GPS and Galileo Receiver, make sure you install octave core and octave-signal in debian systems. Things seems to work at least for PRN, fix point had not been tested Some sampled data can be obtained from: http://downloads.qi-hardware.com/people/kristianpaul/GNSS_signal_records.tar.gz Will be nice also take a look to the code at: http://kom.aau.dk/~borre/matlab/