new anechoic chamber results and comparison with field and ... · new anechoic chamber results and...

1IGS Meeting Bern 2004 Görres et al.: New anechoic chamber results and comparisons ...

New anechoic chamber resultsand comparison

with field and robot techniques

B. Görres, J. Campbell, M. SiemesGeodätisches Institut der Universität Bonn

M. BeckerUniversität der Bundeswehr, München


German bench mark test 2002

Trimble microcenteredwith Ground PlaneTRM33429.20+GP

Leica AT withRadome

LEIAT303 LEIC

Leica AT 502

LEIAT502

Trimble Zephyr geodetic

TRM39105.00

Novatel 503 Choke Ring

with Radome

NOV503 NOKE

�Feldmann-Westendorff 2002)

Motivation: get better insight into the performance of different calibration methods

by calibration of a set of identical antennas at different institutions

GNPCVrobot –absolute

University ofHannover

not availablein spring ´02

chambertest

University ofBonn

Bernese GPSSoftware

relative fieldcalibration

University ofBonn

WaSoft/Kalibrelative fieldcalibration

University ofDresden

WaSoft/Kalibrelative fieldcalibration

State Survey...Niedersachsen

GNPCVrobot –absolute

Geo++Garbsen

usedSoftware

CalibrationMethodInstitution


German bench mark test 2002Results for Leica AT303

(Schmid et al. 2002)


0

0,20,4

0,60,8

11,2

1,41,6

(mm

)

IfE Geo++ LGN TUD GIB

RMS(Ele) L1 RMS(Ele) L2

German bench mark test 2002Results for Leica AT303

(elevation-dependent PCV)

the robot measurements (IfE and Geo++) agree on the level of 1mm

the standard field calibrations display larger variations of 2 mm (L1) and 4mm (L2)

? Confirmation of absolute results by an independent technique and identical antenna ?


EMV-Testzentrum der Bundeswehr in Greding

Largest anechoic chamber in Europe

• 41 x 16 x 14 m

• absorbing material suited for

frequencies > 0.5 GHz


GDI-bus

received GPS signal

trans

mitt

edsi

gnal

L1/L2

network analyser

test antenna

s � 18 m

Antenna measurement setup (pilot phase)

in the Greding chambertransmitting

antenna

control of themotion of

antenna mount


dr(�,�) = a · ro + �·d�(�,�)

with PCO: a(�) = (ax, ay, az)

Antenna Calibration Model

Two - Step Processing

1. Estimation of mean phase center offset (PCO) a with respect to the ARP: � d�(�,�) ² = Min!

2. PCV directly (no fit required!)

ARP

E

a

PCV =d� * � /360°

az

axr0

x

z

�

IdealePhasenfront

reale Phasenfront


geometric situation within the Chamber setup (pilot phase)

to get information about the scatter:

3a. Definition of a model function for the PCVe.g.: harmonic function dr(�) = � (akcos � + bksin �) , k = 0,...3, or 5

3b. Reprocessing of step 1 and re-estimation of normalized RMS

=> ay , az

=> ax , az

Estimation of PCO and PVC


Antenna Type IGS-Code

Trimblecompact

Trimble Zephyrgeodetic

stealth groundplane(anti-reflex)

LEIAT504 Dorne Margolin Antennawith chokerings(designed after D/M T)

LEIAT303_LEIC micropuls antennawith chokerings(identical to AT503)

TRM22020.00+GP with groundplane

TRM41249.00

Trimble geodetic TRM14532.00

Leica AT 303

Leica AT 504

Tested Antenna Types


-10

-8

-6

-4

-2

0

2

4

6

8

-90 -75 -60 -45 -30 -15 0 15 30 45 60 75 90

Zenit [Grad]

Phas

e [m

m]

Leica AT303 Leica AT504 Tr Geod Tr Zephyr Tr Compact

Phase pattern L1 (Elevation - Dependence)

measureded PCV values, no fitting function !


-10

-8

-6

-4

-2

0

2

4

6

8

-90 -75 -60 -45 -30 -15 0 15 30 45 60 75 90

Zenit [Grad]

Phas

e [m

m]

Leica AT303 Leica AT504 Tr geod Tr Zephyr Tr compact

Phase pattern L2 (Elevation - Dependence)

Asymmetry


-3

-2

-1

0

1

2

3

0 30 60 90 120 150 180 210 240 270 300 330 360

Azimut [Grad]

Phas

e[m

m]

Leica AT303 Leica AT504 Tr Geod Tr Zephyr

L1

Phase pattern (Azimuth - Dependence)Elevation 12.5°

-3

-2

-1

0

1

2

3

0 30 60 90 120 150 180 210 240 270 300 330 360

Azimut [Grad]

Phas

e[m

m]

Leica AT303 Leica AT504 Tr Geod Tr Zephyr

L2


0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

Leica AT504 Leica AT303 TRM Comp +GP TRM Geodetic TRM Zephyr

sig0(Azi) L1 sig0(Azi)L2

notavailable

�mm)

Normalized RMS of PCV (mm)gives information about the scatter

after implementation of a harmonic function

0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

Leica AT504 Leica AT303 TRM Comp+GP

TRMGeodetic

TRM Zephyr

sig0(Ele) L1 sig0(Ele) L2

�mm)

of azimuth-dependent PCVof elevation-dependent PCV

�mm)


-6,0

-4,0

-2,0

0,0

2,0

4,0

6,0

8,0

10,0

12,0

0 15 30 45 60 75 90 105 120 135 150 165 180

Elevation [Grad]

PCV

[mm

]

Greding Geo++

Comparison ofPhase pattern L1 (Elevation - Dependence)

Chamber (Greding) - absolut field calibration with robot (GEO++, Hannover)

Leica AT 303 (identical antenna)


-6,0

-4,0

-2,0

0,0

2,0

4,0

6,0

8,0

10,0

12,0

0 15 30 45 60 75 90 105 120 135 150 165 180

Elevation [Grad]

PCV

[mm

]

Greding Geo++

Comparison ofPhase pattern L2 (Elevation - Dependence)

Chamber (Greding) - absolut field calibration with robot (GEO++, Hannover)



-3,0

-2,0

-1,0

0,0

1,0

2,0

3,0

0 30 60 90 120 150 180 210 240 270 300 330 360

Azimut [Grad]

PCV

[mm

]

Greding L1 Geo++ L1

Leica AT 303 L1

Comparison of Phase pattern(Azimuth - Dependence, Elevation 12.5°)

Chamber (Greding) - absolut field calibration with robot(GEO++, Hannover)


-3,0

-2,0

-1,0

0,0

1,0

2,0

3,0

0 30 60 90 120 150 180 210 240 270 300 330 360

Azimut [Grad]

PCV

[mm

]

Greding L2 Geo++ L2

Leica AT 303 L2


Comparison of the Offsets between Chamber(Greding) and robot (GEO++)

=> �antcal2 = �PCO/PCV

2 + �D2

critical moment:

together with definition of ARP

Leica AT504 L1

-6,00

-4,00

-2,00

0,00

2,00

4,00

6,00

8,00

10,00

12,00

14,00

0 15 30 45 60 75 90 105 120 135 150 165 180

Elevation [Grad]

PCV

[mm

]

Greding L1 Geo++ L1

Leica AT504 L1

-8,00

-6,00

-4,00

-2,00

0,00

2,00

4,00

6,00

8,00

10,00

12,00

14,00

0 15 30 45 60 75 90 105 120 135 150 165 180Elevation [Grad]

PC

V [m

m]

Greding L1 Geo++ L1

-6

-4

-2

0

2

4

6


TRM Geodetic TRM Zephyr

(mm

)

D(az) L1 D(az) L2

Residual-Offsets

from best-fit between both patterns


0

0,2

0,4

0,6

0,8

1

1,2

(mm

)


TRMGeodetic

TRM Zephyr

sig0(Ele-comp) L1 sig0(Ele-comp)L2

Scatter between two different PCV patterns

after best-fit

Comparison of PCV

between Chamber (Greding) and robot (GEO++)

0

0,2

0,4

0,6

0,8

1

1,2

(mm

)

LeicaAT504

LeicaAT303

TRM Comp+GP

TRMGeodetic

TRMZephyr

sig0(Az-comp)L1 sig0(Az-comp)L2

not available

elevation-dependent azimuth-dependent


High potential for (receiver) antenna calibration in the anechoic chamber• Absolute calibrations from chamber measurements and robot agree on the

1 mm - level (identical antenna)• Significant variations in quality between antennas of different design• Anechoic chamber and robot permit homogenous distribution

of observations and quality of the PCV resultswith regard to the antenna hemisphere

• Direct representation of the measured PCV values(no fitting function needed)=> possibility to study the characteristics of the patterns in detail

Future: Develop operational procedure for chamber measurements by improved control of the motion of antenna mount => measure the whole hemisphere in an automatic mode

Conclusion

new anechoic chamber results and comparison with field and ... · new anechoic chamber results and...

Documents