GPS over SDR

The thought occurred to me that perhaps the RTL-SDR dongle could be used to pick up GPS signals.  GPS L1 is 1575.42 MHz and L2 is 1227.60 MHz, which are within the range of the R820T tuner's 1700-or-so MHz.

Why, you ask?  Because an RTL2832U + R820T dongle is $10, which is a lot cheaper than most of the pluggable GPS modules out there (usually $40+).  If the base system is an SBC anyway, then this route is much more economical and flexible.  This would also have applications in an SBC-based telemetry system.

Wikipedia has the basic details on GPS and the signals used.  The C/A code is 1.023 MHz and the data is 50 bps, so when the SDR is tuned to the carrier this is well within the bandwidth of the RTL2832U.  Oddly enough, the R820T spec notes that it only supports up to 1002 MHz.

The University of Colorado has a useful GPS overview that includes more specifics, such as how to calculate the PRNs.

And of course there's already a guy who's been working on GPS over SDR, one Michele Bavaro.  Development seems to have stopped, though; and the GPS-SDR site has been converted into a lunch scheduler.