Setup and Survey
Receiver Setup
Measure Antenna Height
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4.1.2. Measure Antenna Height
The location of the antenna relative to the point being measured is very important for both surveys
in which the elevation of the points is important and in surveys for horizontal location only.
Horizontal surveys are often larger in area than can reliably fit on a flat plane, therefore the
antenna adjustment must be done in three dimensions and then projected onto a two dimensional
plane.
The receiver calculates the coordinates of the antenna’s phase center. To determine the
coordinates of the station marker, the user must specify the following:
• Measured height of the antenna above the station marker
• Method of measuring the antenna height
• Model of the antenna used
Antennas have two types of measurements:
• Vertical – measured from the marker to the antenna reference point (ARP) located on the
bottom of the receiver at the base of the mounting threads.
• Slant – measured from the marker to the lower edge of the antenna slant height measure
mark (SHMM) located on both end panels of the receiver.
The point to which surveying with GNSS measures is called the Phase Center of the antenna. This
is analogous to the point at which a distance meter measures in a prism. A user must enter the
prism offset to compensate for this point not being at a physical surface of the prism. For a GNSS
antenna, the offset is entered depending on the type of measurement taken.
• For vertical, the offset is simply added to the measured vertical height to produce a “true”
vertical height.
• For slant height, the vertical height must first be calculated using the radius of the antenna,
then the offset can be added.
The offsets are different because of the difference in location between the slant measuring point
and the vertical measuring point.
1. Measure the antenna height above the control point or marker, either the slant height or the
vertical height (Figure).
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