= GlobalPositioningSystem or GPS =
'''Q:''' Is it possible to use GNU Radio to decode GPS signals?BR
'''A:''' Eventually it will be possible. Civilian accuracy GPS takes less bandwidth and processing power then ATSC reception.
- For civilian accuracy, the equivalent of $100 GPS receivers, the signal of interest (C/A) is at 1575.42MHz(L1) with a bandwidth of ~2.046MHz.
- For surveying accuracy, the signals of interest (C/A & P(Y)) are at 1575.42MHz(L1) and 1227.6MHz(L2) with a bandwidth of ~20.46MHz at each frequency.
- For military accuracy, you have to add the restricted decrypting hardware on top of the surveying requirements.
The Complete Specification * U.S. Coast Guard Website (This looks like where civilians should go) * http://www.navcen.uscg.gov/gps/geninfo/ICD-GPS-200C%20with%20IRNs%2012345.pdf * http://www.navcen.uscg.gov/gps/default.htm * GPS Support Center Website (Less flashy website for U.S. military GPS users?) * http://www.schriever.af.mil/GpsSupportCenter/documents/icd_gps_200c_irn001thru005.pdf * http://www.schriever.af.mil/GpsSupportCenter/
Links to papers with details about software GPS implementations * http://www.datafusion.com/gps/baselinereceiver.pdf * http://gps.ece.cornell.edu/swreceiver_paper5_ION.pdf * http://csc.postech.ac.kr/publication/archive/comm-choi2002.pdf * http://www.navsys.com/Papers/
Overview of GPS Operation * http://www.collaborium.org/onsite/jos2000/related/GPS/DECODING.HTM * http://gpsinformation.net/main/gpslock.htm
General GPS Information * http://gpsinformation.net/ * A decent introduction to GPS, and even better, SDR implementations thereof, is "Fundamentals of Global Positioning System Receivers: A software approach", by James Bao-Yen Tsui (ISBN 0-471-38154-3).
SBAS/WAAS/EGNOS/MSAS information here * http://www.faa.gov/ASD/international/GUIDANCE_MATL/2892b_c1.pdf - FAA WAAS Specification (non-canonical link, a C version exists somewhere) * http://gps.losangeles.af.mil/prn/sbas_ranging_codes.htm - currently registered C/A PN codes for SBAS satellites * http://www.rtca.org/downloads/doclist_1004.htm#_Toc86220673 - RTCA/DO-229 (What is this?) * <put your tidbits here>
OpenGNSS Community Information * Mailing List: http://lists.psas.pdx.edu/mailman/listinfo/opengnss * Wiki: http://psas.pdx.edu/GPS/OpenGnssProjects
Projects * There is an OSS implementation of the decoding part in OpenSourceGPS at http://home.earthlink.net/~cwkelley/ * There is a project at the proof-of-concept stage at http://www.kamieniecki.com/krys/gps/ which currently processes simulated signals with software correlators.
The Russian GLONASS * http://www.glonass-ianc.rsa.ru The Russians added needless complications when they selected a silly time-scale for their system and decided to share the spreading codes between satellites. GLONASS also consumes a lot more bandwidth. However, this would be an excellent demonstration of an SDR's adaptability, since a working software GPS receiver has all the necessary components that a GLONASS receiver requires. One just rearranges them differently. GALILEO falls into the same category.
'''Q:''' What about DGPS for GPS positioning accuracy improvement?BR
'''A:''' For the continental US, WAAS is more reasonable. The marine DGPS beacons that operate at LF (~300kHz) would require another RF path and related antenna.
'''Q:''' What about WAAS, EGNOS (Europe), MSAS (Japan / Asia) for GPS positioning accuracy improvement?BR
'''A:''' WAAS is broadcast on the same L1 frequency as GPS itself. So WAAS support is a pure software feature.