New anechoic chamber results and comparison with field and robot techniques

Transcription

1 1 New anechoic chamber results and comparison with field and robot techniques B. Görres, J. Campbell, M. Siemes Geodätisches Institut der Universität Bonn M. Becker Universität der Bundeswehr, München

2 2 German bench mark test 22 Motivation: get better insight into the performance of different calibration methods by calibration of a set of identical antennas at different institutions Institution Calibration Method used Software Leica AT with Radome LEIAT33 LEIC Novatel 53 Choke Ring with Radome NOV53 NOKE Trimble microcentered with Ground Plane TRM GP University of Hannover robot absolute GNPCV Geo++ Garbsen robot absolute GNPCV State Survey... Niedersachsen relative field calibration WaSoft/Kalib University of Dresden relative field calibration WaSoft/Kalib University of Bonn relative field calibration Bernese GPS Software University of Bonn chamber test not available in spring 2 Leica AT 52 LEIAT52 Trimble Zephyr geodetic TRM3915. (Feldmann-Westendorff 22)

3 German bench mark test 22 Results for Leica AT33 IGS Meeting Bern 24 Görres et al.: New anechoic chamber results and comparisons... (Schmid et al. 22) 3

4 4 German bench mark test 22 Results for Leica AT33 (elevation-dependent PCV) (mm) 1,6 1,4 1,2 1,8,6,4,2 IfE Geo++ LGN TUD GIB RMS(Ele) L1 RMS(Ele) L2 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?

5 5 EMV-Testzentrum der Bundeswehr in Greding Largest anechoic chamber in Europe 41 x 16 x 14 m absorbing material suited for frequencies >.5 GHz

6 Antenna measurement setup (pilot phase) IGS Meeting Bern 24 Görres et al.: New anechoic chamber results and comparisons... 6 transmitting antenna in the Greding chamber L1/L2 test antenna s 18 m transmitted signal GDI-bus network analyser control of the motion of antenna mount received GPS signal

7 7 Antenna Calibration Model PCV = dϕ * λ /36 z E Ideale Phasenfront a x r β reale Phasenfront dr(α,β) = a r o + λ dϕ(α,β) with PCO: a(ϕ) =(a x, a y, a z ) a a z ARP x Two - Step Processing 1. Estimation of mean phase center offset (PCO) a with respect to the ARP: Σ dϕ(α,β) ² = Min! 2. PCV directly (no fit required!)

8 8 Estimation of PCO and PVC geometric situation within the Chamber setup (pilot phase) => a y, a z => a x, a z to get information about the scatter: 3a. Definition of a model function for the PCV e.g.: harmonic function dr(β) = Σ (a k cos β + b k sin β), k =,...3, or 5 3b. Reprocessing of step 1 and re-estimation of normalized RMS

9 9 Tested Antenna Types Antenna Type IGS-Code Trimble compact TRM222.+GP with groundplane Trimble Zephyr geodetic TRM stealth groundplane (anti-reflex) Trimble geodetic TRM Leica AT 54 Leica AT 33 LEIAT54 LEIAT33_LEIC Dorne Margolin Antenna with chokerings (designed after D/M T) micropuls antenna with chokerings (identical to AT53)

10 1 Phase pattern L1 (Elevation - Dependence) measureded PCV values, no fitting function! 8 Leica AT33 Leica AT54 Tr Geod Tr Zephyr Tr Compact Phase [mm] Zenit [Grad]

11 11 Phase pattern L2 (Elevation - Dependence) 8 Leica AT33 Leica AT54 Tr geod Tr Zephyr Tr compact 6 4 Asymmetry 2 Phase [mm] Zenit [Grad]

12 12 Phase pattern (Azimuth - Dependence) Elevation Leica AT33 Leica AT54 Tr Geod Tr Zephyr L1 3 2 Leica AT33 Leica AT54 Tr Geod Tr Zephyr L2 P h a s e [m m ] 1-1 Phase [m m ] Azimut [Grad] Azimut [Grad]

13 13 Normalized RMS of PCV (mm) gives information about the scatter after implementation of a harmonic function of elevation-dependent PCV of azimuth-dependent PCV,35,35,3,3,25,25,2,15,2,15 not available,1,1,5,5 (mm) Leica AT54 Leica AT33 TRM Comp +GP TRM Geodetic TRM Zephyr (m m) (mm) Leica AT54 Leica AT33 TRM Comp +GP TRM Geodetic TRM Zephyr sig(ele) L1 sig(ele) L2 sig(azi) L1 sig(azi)l2

14 14 Comparison of Phase pattern L1 (Elevation - Dependence) Chamber (Greding) - absolut field calibration with robot (GEO++, Hannover) Leica AT 33 (identical antenna) 12, Greding Geo++ 1, 8, 6, PCV [mm] 4, 2,, -2, -4, -6, Elevation [Grad]

15 15 Comparison of Phase pattern L2 (Elevation - Dependence) Chamber (Greding) - absolut field calibration with robot (GEO++, Hannover) Leica AT 33 (identical antenna) 12, Greding Geo++ 1, 8, 6, PCV [mm] 4, 2,, -2, -4, -6, Elevation [Grad]

16 16 Phase pattern (Azimuth - Dependence) Elevation 12.5 Comparison of Chamber (Greding) - absolut field calibration with robot (GEO++, Hannover) Leica AT 33 (identical antenna) Greding L1 Geo++ L1 Greding L2 Geo++ L2 3, 3, 2, Leica AT 33 L1 2, Leica AT 33 L2 1, 1, PCV [m m], PCV [m m], -1, -1, -2, -2, -3, Azimut [Grad] -3, Azimut [Grad]

17 17 Comparison of the Offsets between Chamber (Greding) and robot (GEO++) Leica AT54 L1 Leica AT54 L1 PCV [mm] 14, 12, 1, 8, 6, 4, 2,, -2, -4, -6, -8, Elevation [Grad] Greding L1 Geo++ L1 PCV [mm] 14, 12, 1, 8, 6, 4, 2,, -2, -4, -6, Elevation [Grad] Greding L1 Geo++ L1 6 4 Residual-Offsets from best-fit between both patterns critical moment: (mm) 2-2 Leica AT54 Leica AT33 TRM Comp +GP TRM Geodetic TRM Zephyr => σ antcal2 = σ PCO/PCV2 + σ D 2-4 together with definition of ARP -6 D(az) L1 D(az) L2

18 Comparison of PCV IGS Meeting Bern 24 Görres et al.: New anechoic chamber results and comparisons between Chamber (Greding) and robot (GEO++) elevation-dependent azimuth-dependent sig(ele-comp) L1 sig(ele-comp)l2 sig(az-comp)l1 sig(az-comp)l2 1,2 1, (mm),8,6,4,2 (mm), 8, 6, 4, 2 not available Leica AT54 Leica AT33 TRM Comp +GP TRM Geodetic TRM Zephyr Leica AT54 Leica AT33 TRM Comp +GP TRM Geodetic TRM Zephyr Scatter between two different PCV patterns after best-fit

19 19 Conclusion 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 results with 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