GlobalPositioningSystem

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Global Positioning System (GPS)

GNU Radio can be used to create GNSS receivers. The DBSRX daughterboard for the USRP is capable of receiving signal from all contemporary GNSS systems.

Requirements

  • 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)
  • GPS Support Center Website (Less flashy website for U.S. military GPS users?)

Links to papers with details about software GPS implementations

Overview of GPS Operation

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).
  • http://gpstrackit.com/blog/
  • A regularly updated blog on the applications of GPS and GIS technology

SBAS/WAAS/EGNOS/MSAS information here

OpenGNSS Community Information

Projects

The Russian GLONASS

  • http://www.glonass-ianc.rsa.ru/pls/htmldb/f?p=202:1:12061333542270124939 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&A

Q: What about DGPS for GPS positioning accuracy improvement?

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?

A: WAAS is broadcast on the same L1 frequency as GPS itself. So WAAS support is a pure software feature.