A Software GPS decoder, going from raw 1-bit ADC samples to position fix. This isn't designed to be super-fast, it is designed to let you experiment and improve the methods used, and test out new ideas.

It can also serve as a known-to-work implementation for you to compare your own implmentation against. For me, it was designed for testing algorthms before moving to an FPGA implementation.

If you want to test it out:

• Build the fsgps program

• Download the data file from http://www.jks.com/gps/gps.html

• Process it with the following command:

  fsgps -s 5456000 -i 4092000 gps.samples.1bit.I.fs5456.if4092.bin

After a while you should start seeing location fixes

01, LOCKED, YES,YES, 1609, 77797, 4688, 269, 50 7 24 8 12345 02,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 03,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 04,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 05, LOCKED, NO, NO, 0, 53294, 4676, 921, 39 2 0 2 ....5 06,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 07,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 08,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 09,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 10,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 11,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 12,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 13,ACQUIRE, NO, NO, 0, 5, 5404, 0, 8 0 -1 0 ..... 14,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 15,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 16, LOCKED, NO,YES, 1609, 77797, 4683, 436, 18 2 29 3 12.4. 17,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 18,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 19,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 20,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 21, LOCKED, YES,YES, 1609, 77797, 4683, 47, 27 7 24 3 12345 22,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 23,ACQUIRE, NO, NO, 0, 0, 0, 0, 11 0 -2 0 ..... 24,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 25, LOCKED, YES,YES, 1609, 77797, 4682, 242, 3 7 24 2 12345 26,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 27,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 28,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 ..... 29, LOCKED, YES,YES, 1609, 77797, 4688, 946, 7 7 24 8 12345 30, LOCKED, YES,YES, 1609, 77797, 4690, 741, 46 7 24 10 12345 31, LOCKED, YES,YES, 1609, 77797, 4687, 430, 62 7 24 7 12345 32,ACQUIRE, NO, NO, 0, 0, 0, 0, 0 0 -2 0 .....

Location is ( 10796441.72686, -11059550.95575, 21468769.87626) @ 466786.68844515 Location is ( 25624920.03297, 5493913.05874, 6376813.14970) @ 466786.68314817 Location is ( 17562608.84385, 17600783.06751, 9306656.31975) @ 466786.68228779 Location is ( 12436678.35329, 8851464.38357, 21813028.15234) @ 466786.68876178 Location is ( 18466438.20510, 6615544.19174, 17512994.82941) @ 466786.69042944 Location is ( 20893698.98803, -8968194.45015, 14090804.00502) @ 466786.68741330

Solved is ( 3851785.003462, -78309.097013, 5066312.772752) @ 0.003504 (alt 6364739.204313) Lat/Lon/Alt : 52.934773, -1.164697, 176.8

Signals from eight space vehicles have been obtained, but three have had marginal reception.

SV 01 has a lock, and all NAV data retrieved SV 05 has a lock, and only a minimal amount of data has been received. SV 13 was attempted to be locked, but the lock was dropped as good BPSK data was not being received. SV 16 has a lock with some data, so must have lost sync SV 25 has a lock, and all NAV data retrieved SV 29 has a lock, and all NAV data retrieved SV 30 has a lock, and all NAV data retrieved SV 31 has a lock, and all NAV data retrieved

The calcuated locations of the space vehicles are printed, as well as the ECEF solution for position: 3851785.003462, -78309.097013, 5066312.772752

With the last Lat/Lon/Alt fix of:

Lat/Lon/Alt : 52.934773, -1.164697, 176.8