Influence of using individual GPS receiver antenna ...

Influence of using individual GPS receiver antenna calibrations

on 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: [email protected]

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