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A field test procedure to
check GNSS antenna
calibration parameters
Ulla Kallio, Markku Poutanen, Hannu Koivula, Sonja Nyberg,
Paavo Rouhiainen, Ville Nikkonen
EMRP SIB60, Portugal 2014
Questions
• How well the individual antenna calibration values are valid
in the field ?
• What is the consistency between two sets of calibration
tables?
• Can we solve for the residual offsets of a GNSS-antenna?
• Residual offsets of the antenna should be zero if individual calibration values are
used in data processing. Some offsets may still be present. We call them residual
offsets.
• What is the effect of the changing the calibration table on
coordinates?
L1 chamber PCC minus robot PCC on pillar
440 for antenna11754 in doy 185 2014
L2 chamber PCC minus robot PCC on pillar
440 for antenna 11754 in doy 185
PCC in coordinates (L1)
Robot
Chamber
North
East
Up
RTKlib zero baseline between
calibration tables
Bernese zero baseline between
calibration tables
Simple test procedures
• Rotating the antennas without tilting (absolute N and E)
• Antenna swapping (relative)
• Comparing with ground truth (distances, height
differences, coordinate differences)
• Permutation method (relative)
• Antenna circulation (on three or more points)
• Full roving method (Bányai)
• Circulating and rotating antennas in a micro network
(relative Up, absolute N, E)
Our test procedure
• Measurements: Each antenna visits every pillar. On some
pillars antennas are rotated about the vertical axis 180
degrees.
• Session solutions with Bernese separately with L1 and L2
• SINEX files
• Coordinates and covariance matrices are combined into the
final solution with residual offset parameters for antennas
• The datum defect is solved for by using Moore Penrose pseudo
inverse of normal matrix or by constraining the parameters.
• Residual offsets and their covariance matrices are converted to
NEU
• Statistical significances of the residual offsets are tested
• Height differences between antenna pairs are compared with
levelled height differences
Revolver as a part of the Metsähovi
pillar network
The system of circulating and
rotating the antennas on
pillars (plan)
2
7
1
6
3
5
4
8
1
6
8
5
2
4
3
7
-1
-8
-7
-6
-5
-4
-3
-2
1
8
7
6
5
4
3
2
-2
-1
-8
-7
-6
-5
-4
-3
2
1
8
7
6
5
4
3
3
2
1
8
7
6
5
4
-3
-2
-1
-8
-7
-6
-5
-4
4
3
2
1
8
7
6
5
-4
-3
-2
-1
-8
-7
-6
-5
5
4
3
2
1
8
7
6
5
4
3
2
1
8
7
6
6
5
4
3
2
1
8
7
6
5
4
3
2
1
8
7
7#
6#
5#
4#
3#
2#
1#
8#
7#
6#
5#
4#
3#
2#
1#
8#
8
7
6
5
4
3
2
1
8
7
6
5
4
3
2
1
Measurement configuration
how we really measured
rec serial no
456285
456222
456210
456228
456260
456261
456263
456251
session
doy/marker
0440
0504
14000
14060
14120
14240
14300
14360
session1
185-187
11754
11772
-CR13995
-11988
11194
11963
11770
11959
session2
189
11959
11194
-11754
-CR13995
11988
11772
11963
11770
session3
191
11770
11988
-11959
-11754
CR13995
11194
11772
11963
session4
193-194
11963
CR13995
-11770
-11959
11754
11988
11194
11772
session5
196,224
11772
11754
-11963
-11770
11959
CR13995
11988
11194
session6
198
11194
11959
-11772
-11963
11770
11754
CR13995
11988
session7
200-201
11988
11770
-11194
-11772
11963
11959
11754
CR13995
session8
203
CR13995
11963
-11988
-11194
11772
11770
11959
11754
session9
205
11754
-11772
CR13995
11988
-11194
11963
11770
11959
session10
207-208
11959
-11194
11754
CR13995
-11988
11772
11963
11770
session11
210
11770
-11988
11959
11754
-CR13995
11194
11772
11963
session12
212
11963
-CR13995
11770
11959
-11754
11988
11194
11772
session13
214-215
11772
-11754
11963
11770
-11959
CR13995
11988
11194
session14
217
11194
-11959
11772
11963
-11770
11754
CR13995
11988
session15
219
11988
-11770
11194
11772
-11963
11959
11754
CR13995
session16
221-222
CR13995
-11963
11988
11194
-11772
11770
11959
11754
Bernese processing
• Separately L1 and L2 daily solutions
• Robot (IfE, Univ. Hannover) and chamber (IGG, Univ. Bonn) individual
absolute calibration tables
• Bernese GNSS software version 5.2.
•
•
•
•
Double-difference approach
IGS final orbits and earth orientation parameters.
Ambiguities were solved using the sigma strategy
The troposphere using the Global Mapping Function. (Site specific troposphere parameters
were not estimated)
• Antenna orientation table in use for rotated antennas
• Separate solutions for observation cut-off in 10 and 15 degrees.
• The datum was defined by constraining one of the pillar points (440) to its
ITRF2008 coordinates in mid-epoch of the measurement campaigns.
• Together eight SINEX files for each measurement day.
• L1 and L2, two calibration tables, two cut of angles
Variation in North on pillars 14000,14060,14120
and 504 The antenna orientation table were in use during Bernese
processing-> there shouldn’t be jumps due to the antenna
orientation
Robot L1
mm
14000 and 14060
rotated 180º
Chamber L1
14120 and 504
rotated 180º
Robot L2
Chamber L2
Estimation of residual offsets
Structure of the design matrix A
for three sessions
Functional model for a session
0440-0504
0440-1400
X 504 − X 440 + O 772 − O 754 = ∆ X 440 , 504
0440-1406
0440-1412
X 000 − X 440 + RO 995 − O 754 = ∆ X 440 , 000
0440-1424
X 060 − X 440 + RO 988 − O 754 = ∆ X 440 , 060
0440-1430
0440-1436
X 120 − X 440 + O194 − O 754 = ∆ X 440 ,120
X 240 − X 440 + O 963 − O 754 = ∆ X 440 , 240
X 300 − X 440 + O 770 − O 754 = ∆ X 440 , 300
X 360 − X 440 + O 959 − O 754 = ∆ X 440 , 360
Results:
Residual offsets, NE absolut, Up relative
Results:
Relative residual offsets
11194-11963
11772-11959
Comparison of the GPS height differences
between antenna pairs with the ground truth
11194-11963
After Bernese
Residual offset corrected
Robot L1
Chamber L1
11772-11959
Robot L2
Chamber L2
Comparison of the GPS height differences
between antenna pairs with the ground truth
After Bernese
Residual offset corrected
Comparison of pillar height differences in
Revolver with ground truth
mm
The mean height of the Revolver
pillar points is subtracted before
comparison
Residual offsets are corrected
Revolver pillars
mm
Residual offsets are not corrected
440
Chamber L2
Comparison of pillar height differences
in Revolver with ground truth
mm
• All height differences (altogether
28) are compared with levelled
height differences
• before applying the
corrections and
• after applying the corrections
mm
Height differences from 440
Height differences between Revolver pillars
• The pillar 440 has different
multipath environment than the
Revolver pillars.
• The site specific multipath
environment doesn’t change
significally between sessions
• We can separate the influence of
antenna/antenna calibration table
from multipath
Future plans
• To process the data gathered in July 2014 with splitted sessions in
order to find out the minimum time needed for the session
• To analyse the data with simpified configurations (swap and rotate) in
order to see if the residual offsets could be found quicker
• To develope (using the data already gathered) the test that can be
performed in reasonable time for practical use:
• It can be for example:
• Simple rotation and swapping with few sessions (few times a year or when needed) for
antenna pairs or group of antenna aimed to use in same project
• Or ground truth and reference antenna and rotation method
• If test results show significant residual offsets
• If the antenna is broken, change antenna
• If antenna is unbroken, use full permutation and rotating test or repeat the simple one
• If residual offsets are still more than the given
limits,
New robot or chamber calibration of the
antenna is needed
Acknowledgements
We gratefully acknowledge funding from
the European Metrology Research
Program (EMRP). The EMRP is jointly
funded by the EMRP participating
countries within EURAMET and the
European Union.

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Transcription

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