Observation of L1-SAIF Signal inAustralia
Yong LiENRI Workshop, Tokyo, June 4-5, 2015

Agenda• Introduction• Experiment configuration• Experiment results• Concluding remarks

Project backgroundL1-SAIF aims to provide wide area differential corrections
to GPS uses with a target accuracy of 1m (horizontal).
To investigate potential use of L1-SAIF services inAustralia, a collaboration project between UNSW andENRI has been established.

Schedule of the project
Data collection: September to November 2014
Data analysis: December 2014 to January 2015
Draft report: February 2015
Final report: March 2015

Project purpose
Through analysis on the three month continuous data, theproject aims to study:Ø Phase I: observation and characterisation ofMSAS/QZSS augmentation signal.
Ø Phase II: observation and modelling of the ionosphereusing a GNSS ground observation network.
This investigation would give the information to support
expansion of GNSS wide area augmentation service tothe Asia region.

Outline of the project
The L1-SAIF messages from QZSS and MSAS werecollected at two stations, in Sydney and Melbourne,
during September to November in 2014.
As the first step, the visibility of the QZSS and MSAS
satellites in Australia is evaluated from the collecteddata.
This study can provide a pattern of the real L1-SAIF signals
in the Australian region – its visibility and signal strength.

Experiment configuration
The Javad Alpha GNSS receiver and Leica AS10 antenna
were utilised in Sydney.
Javad Delta receiver and GrAnt-G3T antenna were used inMelbourne.

GNSS receivers and antennas
place/devices
ReceiverSydneyMelbourne

Javad Alpha

Javad Deltaantenna

Leica AS10JavadG3TGrAnt-Data collection toolsThe Javad NetView program was used to configure the receivers andstore the data onto the hard disk of the host computer via serial port.

Antenna setup

Sydney station

Melbourne station

Recorded observations
The GNSS raw measurements were recorded, signallevels, carrier phase measurements, pseudoranges; andDoppler.
Observations of QZSS in Sydney at GPST = 2014- 9-1 00:00:00

Data analysis procedure• The GNSS raw measurements wererecorded in Javad JPS format.
• The RTKIB version 2.4.3 app(RTKConv) was used to convert theJPS files into RINEX files (v3.02 andv2.10).
• The RINEX 3.02 files were processedusing RTKLIB app (RTKPlot) forvisibility analysis.
• The TEQC software was used toanalyse the ionosphere of L1-SAIFsignals from RINEX 2.10.

L1-SAIF visibility and signal level analysis
The results below are visualised: elevation of QZSS, signal
level of L1_SAIF, and code-phase multipath of L1-SAIF.
From Figures it can be seen that the SNR >40dB during thetime J01 at high elevation at the Sydney station(because of the tree near the antenna).
However, from Figures the L1-SAIF signal is strong of SNR> 40dB most of the time at the Melbourne station
because the antenna has an unobstructed sky view.

Visibility plot at Sydney on 2014-09-01

Visibility plot at Melbourne on 2014-09-01

The signals attenuation under the tree shadow
The tree is about 3m
away and has a tall ofabout 3~4m above theantenna, which makesa shadow of about
45deg low, which
attenuates the QZSSJ01 signals underelevation of 45deg.

L1-SAIF ionosphere analysis
The ionospheric delay can be derived from the combination of L1 andL2 carrier phase measurements (Estey and Meertens 1999),

The time-rate of change of ionospheric delay is defined as

The ionospheric delay observable calculated by TEQC is obtained by

Estey L.H. and Meertens C.M (1999), TEQC: The Multi-Purpose Toolkit for GPS/GLONASS Data, GPS Solutions, 3(1):42-49.

Ionospheric delay at Sydney on 2014-09-01

Ionospheric delay at Melbourne on 2014-09-01

Ionospheric error analysis
As shown in Figures, the ionospheric delay of J01 varies
rapidly around 2:00 (GPST, = AET12:00), which means
the ionosphere is relatively active during this period oftime. However the ionospheric delay does not change somuch around 19:00 (GPST = AET5:00), indicating thatthe ionosphere is calm during this period of time.

Concluding remarks
The L1-SAIF signals can be received for most of the day. Data gaps
mainly are due to: (a) the QZSS J01 setting below the horizon; (b)the tree near the antenna at the Sydney station blocked low
elevation signals from the northwestern direction.
The L1-SAIF signal is strong, with SNR > 40dB for most of the time at
the Melbourne station because the antenna has an unobstructed skyview. SNR >40dB during the time J01 was at high elevation wasalso observed at the Sydney station.
The SNR and multipath of L1-SAIF and L1C are similar. They have thesame trend – the lower the elevation the smaller the SNR, and thelower the SNR the larger the MP.
The ionospheric delay of J01 can reflect ionospheric activity, forexample the ionospheric delay does not change around 19:00(GPST) indicating that the ionosphere is calm during this period oftime.

Further work
(1) The ionosphere correction parameter transmitted by L1-SAIF is valid

only for the Japan region. Positioning with L1-SAIF can obviously
improve solution accuracy in Tokyo. However it is necessary toextend the correction coverage area to the south Asia and Pacificregions.
(2) Use of the existing GNSS observation network in Australia canderive the ionospheric delay parameters, and be used to derive thecorrection messages for the Australian region.
(3) With the L1-SAIF correction generated for positioning in Australia,
tests can then be conducted on different platforms – such a landvehicles, vessels, and airplanes – to verify the position accuracyimprovement.
(4) The signal attenuations by the tree are different on L1-SAIF andL1C – more attenuation on L1-SAIF than L1C. More investigations
are needed for the exact reasons of this difference.

Thank you !