Selective Availability: the intentional degradation of the timing and position information transmitted by a GPS satellite

PDOP: (the position dilution of precision); describes the amount of error due to the geographic position of the GPS satellites.

Multipath: an error caused by a delay in the signal due to reflections from the surfaces before reaching the receiver.

DGPS: (differential GPS); a method of using a ground based correction in addition to  the satellite signals to determine position.

  • In normal everyday use accuracy of GPS is around 10-15 meters.
  • This is because of different factors causing delays in the transmission.
  • The biggest source of error was intentional.
  • The united states introduced selective availability to make the signal less accurate so that no one could use the GPS against the united states.
  • Selective availability introduced two errors.  

TYPES OF ERRAS 

  • In normal everyday use accuracy of GPS is around 10-15 meters.
  • This is because of different factors causing delays in the transmission.
  • The biggest source of error was intentional.
  • The united states introduced selective availability to make the signal less accurate so that no one could use the GPS against the united states.
  • Selective availability introduced two errors.  

SELECTIVE AVAILABILITY

  • In 2000, the United States decided to turn the selective availability off.
  • They also announced that they do not plan to make future satellites with the feature.
  • However the public GPS will still be less accurate than the military's.
  • The arrangement of satellites can have an effect on determining position.
  • The further satellites are spread out the more accurate the measurements will be
  • On the other hand the less spread out satellites are the less accurate the measurements will be.
  • MORE INFORMATION

This Content Originally Published by a land surveyor to Land Surveyors United Network

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