Antenna Calibration

The antenna calibration process attempts to answer very important question where do I receive the signal? The result is an offset value applied to the antenna reference point (ARP).

What is Antenna Calibration?

Why do I need calibrations?

By not receiving the signal exactly at the phase center, antenna introduces several millimeters to centimeters of phase advance/delay which cause range errors. Omitting calibrations may introduce significant error (particularly in height component) when processing long baselines or when combining multiple antenna models.

Antenna calibration values are typically used for precision measurements (surveying, geodesy, precise monitoring, etc.); in GIS, such calibration is usually not took into account.

Calibration Models: Relative or Absolute

In a relative calibration model, all antenna offsets (PCO) and phase center variations (PCV) are computed with respect to a reference antenna which is normally assigned zero PCV values.  A relative calibration is therefore biased by the phase advance/delay experienced by the reference antenna.

In an absolute calibration model, all antenna offsets and phase center variations are independent of the reference antenna.  To conduct an absolute calibration, the antenna being tested is moved via a robot so that a particular satellite is received at different angles by the test and reference antennas.  This angular separation enables cancelation of the reference antenna effects, leaving behind only the antenna offsets and phase center variations of the test antenna.

Since these 2 methods are very different in their approach, they cannot be combined.

Why Go to Absolute?

Since absolute calibration model offers a better/fuller description of phase behavior, the GNSS community is evolving towards using absolute antenna calibration.

Typical robot used for absolute antenna calibration.

Article: 000111

Related Products: EZSurv

Last Update: 2016-07-14 18:44:15

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