Methods for GNSS measurement

Since the 1980s, several methods and techniques for GNSS measurement have been developed. It has opened many new areas of application, in both research and commercial activities.

Basic principles for GNSS measurements

Most applications are based on the same basic principles:

  • GNSS measurement requires a clear view of satellites. The distance between receivers and satellites is determined using code measurement and/or carrier phase measurement on the GNSS signal. See also overview comparison of code and carrier phase measurement.
  • Code measurement and carrier phase measurement are affected by different sources of error. The impact of the sources of error can be reduced by measuring against many satellites, or by trying to estimate or model the sources of error.
  • Positioning of the GNSS receiver in relation to the satellites can be done with one or more receivers. If more than one receiver is used, some of them can be placed over points with an already known position. This is called relative positioning and makes it possible to reduce or eliminate sources of error and thus the measurement uncertainty of the receiver with an unknown position.

High-accuracy GNSS measurements

Geodetic measurement with GNSS today takes place almost exclusively with relative carrier phase measurements, either in real time or with post-processing of the position.

Ground-based GNSS infrastructure, for example SWEPOS, is common way of collecting and using the information from many GNSS receivers for accurate relative positioning. Such infrastructure enables positioning services which can facilitate or improve the positioning of GNSS users.

With only one receiver available, some sources of error can still be reduced by adding external information about these sources of error. This measurement method is called Precise Point Positioning.

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