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8. GPS in land surveying

principle of GPS



source: https://gisgeography.com/trilateration-triangulation-gps/

systems: GPS (31), Glonass (23), Galileo (22), Beidou (50), QZSS, IRNSS, EGNOS, WAAS ...

major error sources:

  1. orbit
  2. satellite clock offset
  3. atmosphere: troposphere and ionosphere
  4. receiver clock offset
  5. geometry, dilution of precision
  6. multipath
  7. jamming, spoofing


source: http://www.wirelessdictionary.com/Wireless-Dictionary-GPS-Errors-Definition.html

typical accuracy of everyday application versus accuracy requirement in land surveying

in order to reach cm accuracy:

  1. phase measurement instead of code one
  2. relative positioning instead of the absolute one
  3. real-time, communication between the base and rover receivers. Internet or radio.
  4. GNSS-infrastructure (e.g. https://www.gnssnet.hu/)
  5. transformation


source: https://www.e-education.psu.edu/geog862/node/1725

Nowadays many projects in land surveying are done by GPS. It is not really expensive, it might be very efficient but not suitable for everything. Limitations:

  • satellite visibility
  • accuracy, especially the vertical one