Topcon GR-5, Operator'S Manual

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GR-5 Receiver Setup and Survey
GR-5 Operator’s Manual
4-4
Step 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, 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 surveying point that GPS/GLONASS to measure satellite
systems is called the “Phase Center” of the antenna. The antenna
Phase Center is analogous to the calibrated point to which a distance
meter measures inside of a prism; i.e. it cannot be directly measured
to in the field. For precision Topcon GPS/GLONASS antennas
− such
as the one inside the GR-5 − the antenna Phase Center must be
modeled using a detailed calibration in order to achieve optimal
survey results. This model information consists of phase center offset
(PCO) and phase center variation (PCV) components, and is applied
internally by field software such as TopSURV for RTK operations,
and by Topcon Tools software for post-mission operations
1
.
1. This antenna calibration information (PCO and PCV data) does not
need to be entered in the field.