Javad TRIUMPH-1 Operator's Manual page 51

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 verti-
cal height (Figure).
2. Record the antenna height, point name, and start time in the field notes.
www.javad.com
SHMP
88.75
NGS ARP
1. All dimensions are in mm
2. * Reference dimension
3. ARP - Antenna Reference Point
SHMP - Slant Height Measurement Point
Description and Operation
Setup and Survey
Measure Antenna Height
51