Spectra Precision ProMark 800 Reference Manual - Manual (Page 70)

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Precise Surveying - Field Applications & Concepts
To compute the position of the mark instead of the antenna,
it is necessary to instruct the rover to perform an antenna
reduction. In an antenna reduction, the antenna heights are
taken into account when computing the rover position.
Whether you are performing an RTK or post-processing
survey, the antenna heights of both the base and the rover
should be entered in the system so the correct ground
positions can be determined.
There are two different ways of measuring the antenna height:
• Slant height measurement
• Vertical height measurement.
Slant Height
Measurement
Slant measurement is typically performed at the base
because the classical vertical measurement is not possible
owing to accessories (tripod, tribrach, etc.) being usually in
the way of the vertical path from the antenna to the landmark.
Rather than performing a bad vertical measurement, it is a
better idea to use a slant measurement, which is much more
accurate, provided the antenna parameters are also
accurately known and the specific Spectra Precision
measurement tape is used for this purpose.
Measured Vector
Phase Center
Phase Center
Ground Vector
Reference Point
Survey Point
Base
Rover
Base
Antenna
Height
Rover
Antenna
Height