ADWR GPS Equipment and
Surveying Techniques
The Geophysics/Surveying Unit uses Trimble 4800
and R8 GNSS Series survey-grade GPS receivers. The GPS
equipment includes:
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Static GPS Survey in the Pinal AMA
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- 3 Trimble 4800 Rover Receivers
and 3 Trimble TSC1 Controllers
- 1 Trimble 4800 Base Receiver
- 1 Trimble R8 GNSS Rover
Receiver and TSC2 Controller
- 1 Trimble R8 GNSS Base
Receiver and TSC2 Controller
- 1 Trimble Trimmark II Radio
- 1 Trimble HPB450 Radio
- 2 UHF Omnidirectional Antennas
with a 5dB Gain Tip
- 4 SECO 2.000 meter Fixed
Height Tripods
- 2 SECO Adjustable Height
Tripods
- 3 Trimble 1.800 meter Carbon
Fiber Bipods
- 1 Trimble 2.000 meter Carbon
Fiber Bipod
- Trimble Geomatics Office (TGO)
Version 1.63 Software
The Geophysics/Surveying Unit performs three primary types of
GPS surveys to determine the horizontal and vertical position
of discreet points: Static surveys, Real Time Kinematic (RTK)
surveys and Post Processed Kinematic (PPK) surveys.
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WQARF RTK GPS Survey |
The Static survey method requires long
occupation times (1 to 8 hours), multiple receivers logging
data simultaneously, repeat observations, and significant
post-processing to produce final results. The Static survey
method is the most accurate GPS survey technique available
today. The level of accuracy achieved in the final results is
based on a number of factors (e.g. equipment type, occupation
time, baseline distance, satellite availability and
constellation geometry, and physical receiver environment). We
primarily use the Static survey method when performing our
land subsidence measurements.
The Real Time Kinematic (RTK) Survey style
requires very short (seconds to minutes) occupation times and
no post-processing of the GPS data. However, this method
requires that a base station (GPS receiver occupying a
location with known coordinates) is operating and broadcasting
a correction signal that can be received by the GPS rover
receiver. The RTK survey style is used to measure a large
number of survey points, in a relatively small geographic
area, in a short period of time. There is a decrease in the
accuracy of the final result when compared to the static
survey style, but these measurements are not normally used for
land subsidence monitoring.
The Post Processed Kinematic (PPK) Survey style
requires an occupation time of at least thirty seconds. This
method is similar to the RTK Survey style but it does not use
the broadcasting correction signal from the base station. It
uses the static survey data from the base station to post
process the initial point survey data.
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Trimble 4800 RTK Base Station
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The Trimble manufacturer's
published errors  associated with the Static and Real
Time Kinematic Survey Styles for the R8 GNSS and 4800 Series
receivers are:
RTK Errors: +/- 1cm + 2ppm
Horizontal
+/- 2cm + 2ppm Vertical
Static Errors: 5mm + 1ppm (times baseline length)
Horizontal
10mm + 1ppm (times baseline length) Vertical
PPK Errors: 1cm + 1ppm (times baseline length)
Horizontal
2cm + 1ppm (times baseline length) Vertical
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