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G1-m1TM Static White Paper.docx rev 1.0, October 2013
G1-m1TM GNSS Mobile System
Field Testing - Static Case
WWW.GEOMATICS.US
October 2013
© 2013 Geomatics USA, LLC All Rights Reserved
Purpose: This document is for the G1 GNSS system users.
It shows the achieved accuracy of the G1-m1TM system
data in static mode. For instructions on how to acquire
the GNSS data, refer to the G1 receiver quick guide; for
instructions on how to process the acquired data, refer to
the HorusTM software guide.
Requirements: This document presumes that you have
at least one G1 GNSS receiver (the rover). Optionally,
users can collect correction data on a known base station
(the base). Or, you can request to download the
correction data from the closest Continuously Operating
Reference Station (CORS), as described in the HorusTM
software guide.
Note: By GNSS data, we mean raw ranges between the
G1 receiver and the respective GPS/GLONASS satellites in
the form of C/A code and carrier phase observations. The
raw ranges are readily available on a uSD card in the form
of a binary data file after a successful data acquisition
mission using the G1 receive.
Test Objective
The G1-m1TM receiver has an L1-only GNSS engine. It is
capable of acquiring data in static and kinematic
positioning modes. This test is to show the achievable
positioning accuracy of the G1-m1TM system in static
mode, i.e. when the system is stationary over a point for
a while. The G1-m1TM system used is configured for 1-s
interval and GPS-only mode. The antenna used is a G1-
A311TM patch with a 3.75” ground plane.
Figure 1: G1-m1TM System on a mini Tripod over a GCP Check Point
G1-m1TM Field Testing – Static Case
Test Site
The test was conducted in June 2013 at the parking lot of
the Santa Fe Community College in Gainesville, FL. The
site was chosen because of its relative openness and its
suitable satellite visibility, see Figure 2.
Reference Network
A network of three control stations were surveyed with
Trimble 5700 geodetic-grade receivers to establish a
reference for the survey, as shown in Figure 3.
The reference network was adjusted using Trimble
Business Center. The summary of the network adjustment
report is shown in Table 1. The reference network
provides a benchmark solution accurate to a few
millimeters both horizontally and vertically. For the
purpose of this evaluation, we shall consider the reference
network stations to be fixed (errorless.)
GNSS Loop Closure Results Summary
Legs in Loop = 3 Length
(Meter)
ΔHoriz
(Meter)
ΔVert
(Meter) PPM
Pass/Fail Criteria 1
Best 0.001 -0.003 5.743
Worst 0.001 -0.003 5.743
Average Loop 590.814 0.001 0.003 5.743
Standard Error 0.000 0.007 0.000 0.000
Adjustment Statistics
Number of Iterations for Successful Adjustment: 2
Network Reference Factor: 1.00
Chi Square Test (95%): Passed
Precision Confidence Level: 95%
Degrees of Freedom: 3
Post Processed Vector Statistics
Reference Factor: 1.00
Redundancy Number: 3.00
A Priori Scalar: 0.26
Adjusted Geodetic Coordinates
Pt ID Latitude Longitude Height
(m)
Height
Error
(m)
Fixed
NE N29°41'05.37214" W82°26'06.77104" 24.679 ? LLh
NW N29°41'05.61902" W82°26'14.56092" 28.765 0.002
SE N29°41'00.94168" W82°26'07.22740" 23.597 0.002
Adjusted GPS Observations
Observation
ID Observation
A-
posteriori
Error
Residual Standardized
Residual
NE --> NW
(PV3) Az. 272°04'45" 0.543 sec
0.160
sec 0.892
ΔHt. 4.086 m 0.002 m -0.001 m -1.725
Ellip
Dist. 209.577 m 0.001 m 0.000 m 0.657
NW --> SE
(PV1) Az. 126°08'42" 0.420 sec
-0.044
sec -0.267
ΔHt. -5.168 m 0.002 m -0.001 m -1.720
Ellip
Dist. 244.167 m 0.001 m 0.000 m -0.876
NE --> SE
(PV2) Az. 185°08'23" 1.199 sec
-0.327
sec -0.749
ΔHt. -1.082 m 0.002 m 0.001 m 1.705
Ellip
Dist. 136.968 m 0.001 m 0.000 m 0.833
Error Ellipse Components
Point ID Semi-major axis
(Meter)
Semi-minor axis
(Meter) Azimuth
NW 0.001 0.001 120°
SE 0.001 0.001 119°
SFe-NE SFe-NW
SFe-SE
GNVL
Figure 2: Test Site of a Base and Three GCPs
Figure 3: Test Reference Network
Base
NW NE
SE
SFe
15 km
Table 1: Reference Network Adjustment Report Summary
G1-m1TM Field Testing – Static Case
Test Procedures
Two G1-m1TM receivers were used along with a G1-
A311TM antenna in this test. Each receiver was running
on the SFe-NW check point concurrent with two Trimble
base receivers on the SFe-NE and SFe-SE stations which
allowed for acquiring two data sets for testing. Figure 4
shows the satellite visibility and DOPs as acquired by the
G1-m1TM system.
Data Set 1: In this case, the G1-m1TM AAC receiver was
setup on check point SFe-NW. 30 minutes of static data
was collected at 1-s interval, a total of 1972 epochs.
Data Set 2: Receiver G1-m1TM AAA was then setup on the
SFe-NW check point. It collected data for about 15
minutes at 1-s interval, a total of 760 epochs.
Test Results
HorusTM GNSIS post-mission processing software was
used to process the acquired data against the base
station data.
Short vs. Long Baselines: The acquired data was first
processed in static mode and the calculated position was
compared to the ‘known’ surveyed coordinates of the
occupied station (SFe-NW); table 2 summarizes the
results of the static processing of the two data sets.
As shown in Table 2, the results are consistent for the
short baselines between the systems and the SFe base (<
250 m). The horizontal error is in the cm-level, while the
vertical error has maxed to 3 cm.
The long baselines between the systems and the
Gainesville airport CORS station (GNVL) 15 km away yield
mixed results. While cm-level accuracy was not
achievable over the shorter duration of less than 15
minutes, the 30 minute session was, however, acceptable
with cm-level horizontal accuracy and 5 cm vertical.
Baseline DN [m] DE [m] Dh [m]
AAC Receiver
AAC11-SE 0.001 0.009 0.009
AAC11-NE 0.000 0.007 0.000
AAC11-GNVL 0.004 0.002 0.050
AAA Receiver
AAA06-SE 0.007 0.002 0.034
AAA06-NE 0.009 0.003 0.013
AAA06-GNVL 0.021 0.226 0.247
Static vs. Kinematic Data Processing: To evaluate the
behavior of the acquired data between epochs, the static
data sessions were processed one more time in kinematic
positioning mode, i.e. as if the receiver was moving.
As shown in Figure 5, the ground track of the system
position conforms to the results of the static processing.
Apart from a couple of epochs, almost 100% of the
positions were calculated based on carrier phase integer
ambiguity (green color) with a standard deviation and
RMSE in the cm level both horizontally and vertically; this
achievable for both data sets.
The acquired carrier phase ranges did not show any
particular pattern for this case, as shown in Figure 5. The
root-mean-squared error of the carrier phase residuals is
5 mm in this case, as expected.
Figure 4: Satellite Visibility and DOPs during the Test
Table 2: Summary Results of the Static Baselines (6 total)
G1-m1TM Field Testing – Static Case
The ground track and the residual errors, however,
showed some pattern in the longer baseline case, as
depicted in Figure 6. Almost 100% of the carrier phase
ambiguities were not resolved to integer value and a float
solution was used (amber color.)
The quasi-sinusoidal pattern is most likely due to the
atmospheric errors between the GNVL CORS and the SFe-
NW station (~ 15 km). The residual errors are
pronounced more in the up component, which indicates a
higher tropospheric effect. The other possible reason is
the relatively short session duration (~ 30 min.) over the
relatively long baseline length, where satellite-receiver
geometry was not allowed to change to de-correlate the
errors.
Conclusion
The results of this test show that cm-level horizontal and
vertical positional accuracy is achievable with the G1-
m1TM receiver in static mode over short baseline.
Although the collected data was relatively short in time
(only 15&30 minutes), it was adequate to show the
system potential.
On the other hand, cm-level positional accuracy over long
baseline was only achieved with longer data sessions;
sub-foot positional accuracy is always achievable. Longer
static sessions of the G1-m1TM system of two hours or
more is recommended for long baselines.
Figure 5: Ground Track and Residual Range Errors (Short Baseline)
Figure 6: Ground Track and Residual Range Errors (Long Baseline)
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