Interesting. My B 1 is very different, but B 2 is mostly the same. Looks like B 1 may be the ephemeris and B 2 the almanac. Only problem is that 1153 bytes is not enough to hold the 15k bit message. Perhaps this is due to error correction overhead in GPS messages? Another possibility is that only the non-empty part of the almanac is stored.

I bet with some effort we could decipher the format and come up with a homebrewed A-GPS solution. It would work something like this:

- When N810 is connected to the network, fetch the latest ephemeris data once an hour and store it in nvd_data. There are lots of free sources of ephemeris data on the internet.

- Approximate position would default to last known position. Time doesn't need to be very accurate for warm fixes I think.

- If you use the GPS in your N810 within a couple of hours of being connected to the network, time to first fix should be ~10 seconds.

Am I missing something? Is there more to A-GPS than I imagine?

This would be a cool project to work on.