20
www.javad.com
the multiple log files created in AFRM mode.
• Phase – specifies the phase (i.e., constant time
shift) of the multiple log files created in AFRM
mode.
• Enable Oldest Log-file removal – if active, the re-
ceiver will remove the least recent files if no free
space is available in the receiver memory to record
the current file
SETUP AND SURVEY
After configuring the receivers for surveying, each
receiver needs to be setup up and the receiver’s height
measured and the survey can begin. The MinPad pro-
vides quick access for logging data, changing receiver
modes, and viewing general data logging and satel-
lite information during a survey.
A typical GPS survey system consists of a Base sta-
tion set up over a known point and a Rover receiver
set up to be a mobile data collector. After setting up
the Base and Rover receivers, the antenna height
must be measured.
Before collecting data, make sure the Base and
Rover receivers contain a current almanac and cur-
rent ephemeris data.
The Base station must be set up, logging data, and
transmitting data before setting up the Rover receiv-
er. Receiver setup for either post-process or RTK sur-
veys is the same.
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 sur-
veys 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 an-
tenna’s phase center. To determine the coordinates of
the station marker, the user must specify the follow-
ing:
• Measured height of the antenna above the sta-
tion 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 an-
tenna 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 anal-
ogous to the point at which a distance meter mea-
sures in a prism. A user must enter the prism offset to
compensate for this point not being at a physical sur-
face of the prism. For a GNSS antenna, the offset is en-
tered depending on the type of measurement taken.
54.4
88.75
182*
L2 Up Offset: 90.77
L1 Up Offset: 89.19
236.4*
1. All dimensions are in mm
2. * Reference dimension
3. ARP - Antenna Reference Point
SHMP - Slant Height Measurement Point
NOM - North Orientation Mark
ARP
SHMP, NOM
For vertical, the offset is simply added to the mea-
sured 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.
Measure the antenna height above the control
point or marker, either the slant height or the vertical
height.
Record the antenna height, point name, and start
