Influence of using individual GPS receiver antenna calibrations on - - PowerPoint PPT Presentation

Influence of using individual GPS receiver antenna calibrations

• n high precision geodetic positioning, case study: Northern

Surat Basin Queensland 2015 GPS campaign

IGNSS 2016, Sydney, 6 – 8 December 2016

Guorong Hu & Michael Moore Geodesy Section, Geoscience Australia

GNSS antenna types

GNSS antenna Satellite antenna Block I Block II, IIA, …. Receiver antenna Single frequency (mobile phone, low cost GNSS receiver antenna) Dual frequency (high precision geodetic receiver antenna)

iphone GPS antenna

Basic concepts

ARP (Antenna Reference Point) GNSS satellite antenna Zenith Mean Phase Centre

 PCO: Phase Centre Offset, given in NEU components relative to the ARP  PCV: Phase Centre Variation, variation of the actual phase centre with the direction of the arrival of the signal, provided as a function of elevation angle and/or azimuth angle in antenna frame  NRP: North Reference Point, the NRP should be properly oriented to true north for antenna calibration

GNSS receiver antenna

• Relative calibration: Phase centre determinations from a

stationary test pier referenced to a standard (Dorne Margolin choke ring antenna, type T: AOAD/M_T)

• Absolute calibration: calibration where PCO/PCV are

independent of the reference antenna

• Individual calibration: calibration values which are specific

to the antenna serial number

• IGS type mean calibration: calibration values for an antenna

model, where several test samples are separately calibrated and averaged together by IGS antenna working group

• GA type mean calibration ……

Basic concepts

• Relative antenna calibration: 30 June 1996 ~ Nov. 2006
• Absolute antenna calibration: Nov. 2006 ~ present
• Calibration facilities officially recognized by IGS:

GA, Geo++, NGS, Univ. Hannover, Univ. Bonn

• GA was recognized/approved by IGS antenna working group

announced in IGS workshop 2016 in Sydney, Feb 2016

History of antenna calibration of IGS products

• Systematic errors caused by assumptions of relative PCVs:

PCV(AOAD/M_T)=0 & PCV(GNSS sat. antenna)=0

Why relative PCVs to absolute PCVs

• Independent from reference antenna
• High resolution and precision PCVs
• Site and location independent

Advantages of absolute antenna calibration

Two absolute calibration methods:

• Anechoic chamber calibration: using

artificial GPS signals

• Robotic calibration: using real GPS

signals

Absolute GNSS antenna calibration method

Credit: University of Bonn GA’s robotic ACF

• Impact on GPS solutions including:

 Terrestrial scale (global solutions)  Station coordinates  Orbit parameters  Troposphere parameters

Why antenna calibration matter

• Findings of experiment by IGS Antenna WG on reprocessed

global solutions of ~ 200 stations data from 1994 to 2005: Credit: Schmid et al., 2005

PCVs model impacts on global GNSS solutions

• ~ 25 different antenna types
• ~ 145 individual antennas
• > 400 individual calibrations
• Individual calibrated antenna PCV can be accessed at:

ftp://ftp.ga.gov.au/geodesy-outgoing/gnss/products/antenna/

Antennas calibrated at GA as of November 2016

Case study: comparison position impact of using IGS-type mean and individual PCV models

• Data source: Northern Surat Basin QLD Campaign 2015
• Stations: 65
• Antenna types used: 4 (TRM57971.00, TRM55971.00,TPSG3_A1, and

LEIAR10)

• Observed days: 20 days, 15-28 Sept and 13-18 Oct 2016

Antennas for Surat QLD 2015 GPS campaign TRM57971.00 NONE (L1)

Antennas for Surat QLD 2015 GPS campaign TRM57971.00 NONE (L2)

• Significant difference

among different antennae in terms of serial numbers

Antennas for Surat QLD 2015 GPS campaign TPSG3_A1 NONE (L1)

Antennas for Surat QLD 2015 GPS campaign TPSG3_A1 NONE (L2)

Antennas for Surat QLD 2015 GPS campaign LEIAR10 NONE (L1)

Antennas for Surat QLD 2015 GPS campaign LEIAR10 NONE (L2)

Position differences between using IGS-type mean and individual PCV models

• TRM57971.00 NONE antenna better agreement with IGS type

mean

• Maximum position difference is 20.9 mm in vertical

component of site SB56, which is TPSG3_A1 NONE antenna

• Horizontal component position differences are within 3 mm
• Large position differences for vertical component but

correlates with antenna type

Findings from the comparison between IGS type mean and individual PCV

• Should we give up IGS type mean PCV and use individual

PCV models?

• Suggestions: use IGS type mean PCV for IGS stations which

will keep consistency with IGS products and use individual PCV as many as possible for other non-IGS stations

Discussions

Phone: +61 2 6249 9884 Web: www.ga.gov.au Email: guorong.hu@ga.gov.au Address: Cnr Jerrabomberra Avenue and Hindmarsh Drive, Symonston ACT 2609 Postal Address: GPO Box 378, Canberra ACT 2601

Questions?

Special Case: Damaged Antenna – ASH701945E_M__NONE (L2)

Special case: damaged antenna – ASH701945E_M__NONE (L1)

Repeatability of PCV for reference antenna TRM59800.00 NONE (L2)

L2 dPCV < 2 mm

Repeatability of PCVs for reference antenna TRM59800.00 NONE (L1)

L1 dPCV < 1.5 mm

Individual antennas – TRM59800.00__NONE (L1)

• Significant difference

among different antennas in terms of serial numbers

Individual antennas – TRM59800.00__NONE (L2)

Individual antennas – TRM29659.00__NONE (L1)

Individual antennas – TRM29659.00__NONE (L2)

First ever robot calibrated antenna: ASH701945.B__NONE (L1)

First ever robot calibrated antenna: ASH701945.B__NONE (L2)

Individual antennas – TRM57971.00__NONE (L1)

Individual antennas – TRM57971.00__NONE (L2)

• Not all GNSS satellite antenna are luckily calibrated
• Estimation of satellite antenna corrections from IGS re-

processing campaign using global GNSS data

Satellite antenna calibration method

• GA robotic GNSS antenna calibration operational since 2014
• Several antennas previously did not have robot calibrations

Summary and conclusions

• Why we need to do antenna calibrations
• Antenna calibration history
• GA’s antenna calibration facility (ACF)
• Impact on estimated station position when using individual

PCVs

• Summary and discussions

Overview

Credit: www.ngs.noaa.gov