Transcript PowerPoint 簡報

GPS Receiver Calibration Demostration Principle and Data Analysis
Jia-Lun Wang, Shinn-Yan Lin, Yi-Jiun Huang,
Huang-Tien Lin and Chia-Shu Liao
National Time and Frequency Standard Lab.,
Chunghwa Telecommunication Laboratories (TL) , Taiwan
APMP 2012
November 27, 2012
Wellington, New Zealand
Telecommunication Laboratories
Purpose of Calibration
Objective: Realize the measurement of UTC(TL) - UTC(MSL),
using the local and remote equipment
For this purpose, we must calibrate the local and remote
equipment
The colored notation:
Blue: Term to be Measured
Red: Term to be Calibrated
Purple: Calibrated Term
Telecommunication Laboratories
Realize the Measurement of UTC(TL) - UTC(MSL)
Calibrate XS + XR to realize the measurement of UTC(TL) - UTC(MSL)
Local
Ashtech
Z-XII3T
(Z12T)
RINEX to CGGTTS
Cbl Dly = XC
Ref Dly = XP + XO
Int Dly = XS + XR
GPS
XS
GPS
XS
XC
XC
XR
XR
XO
XO
XP UTC(TL)
XP UTC(MSL) RINEX to CGGTTS
Cbl Dly = XC
Ref Dly = XP + XO
Int Dly = XS + XR
Remote
RX
UTC(TL) - UTC(MSL)
= REFGPS(Z12T@TL) - REFGPS(RX@MSL)
Telecommunication Laboratories
Which term should we calibrate?
Telecommunication Laboratories
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Hardware Delay
GPS
Antenna
XS Antenna Delay
XC Cable Delay
GNSS
Receiver
XR Internal Delay
XO Internal Reference Offset
XP 1-PPS Offset
Telecommunication Laboratories
Source
REF
Delay Measurement with Conventional Scheme
GPS
Antenna
XS Antenna Delay
XC Cable Delay
Measure by Time Interval Counter
GNSS
Receiver
XR Internal Delay
XO Internal Reference Offset
Measure by Oscilloscope
XP 1-PPS Offset
Measure by Time Interval Counter
REF
Source
RINEX to CGGTTS
Cbl Dly = XC
Ref Dly = XP + XO
Int Dly = XS + XR
REF - GPS = REFGPS(GNSS Receiver)
Term to be calibrated: internal delay XS + XR
Telecommunication Laboratories
GPS Calibration Exercise Demostration
Motivation:
1. Demonstrate the GPS receiver calibration procedure
2. Reduce uB (5ns) of GPS time transfer link
3. Time Interval Counter (TIC) will be used to specify the
voltage level of PPS signal
Goal:
1. Perform the APMP TC initiative project
2. Realize the measurement of UTC(TL) - UTC(MSL)
3. Helpful to the future GPS receiver calibration campaign
Telecommunication Laboratories
Step 1: Equipment Calibration
Objective:
Calibrate the internal delay of the traveling equipment
Data Analysis:
1. Use P3 (ionosphere free observation), and All-in-view
2. Cut-off elevation angle 30°
3. Convert RINEX to CGGTTS by R2CGGTTS V5.0 software,
distributed by BIPM and output REFGPS(Receiver@Lab) at
CGGTTS format
Telecommunication Laboratories
Cut-off Elevation Angle
Result of the REF - GPS by using PolaRx4 PR0 GNSS receiver
The result will be stable if the elevation angle is large
Elevation angle > 30°
Telecommunication Laboratories
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Step 1: Traveling Equipment Calibration
Goal: Calibrate the internal delay, XS +XR , of the traveling equipment
The hardware delay of Z12T are known a-priori, and all the delay are need to measure
Ashtech
Z-XII3T
(Z12T)
RINEX to CGGTTS
Cbl Dly = XC
Ref Dly = XP + XO
Int Dly = XS + XR
GPS
XS
GPS
XS
XC
XC
XR
XR
XO
XO
XP
UTC(TL)
XP
XS +XR
= REFGPS(Z12T@TL) - REFGPS(P965@TL)
Telecommunication Laboratories
Septentrio
PolaRx4 PRO
(P965)
RINEX to CGGTTS
Cbl Dly = XC
Ref Dly = XP + XO
Int Dly = 0
Step 2: Remote Equipment Calibration
Objective:
Calibrate the internal delay of the remote equipment
This is similar with step 1, but the terms to be calibrated are
different. One can compare these two cases.
Telecommunication Laboratories
Step 2: Remote Equipment Calibration
Goal: Calibrate the internal delay, XS + XR, of the remote equipment RX
Need to measure the hardware delay of the remote equipment
P965@MSL
RINEX to CGGTTS
Cbl Dly = XC
Ref Dly = XP + XO
Int Dly = XS + XR
GPS
XS
GPS
XS
XC
XC
XR
XR
XO
XO
XP
UTC(MSL)
RX@MSL
XP
XS +XR
= REFGPS(P965@MSL) - REFGPS(RX@MSL)
Telecommunication Laboratories
RINEX to CGGTTS
Cbl Dly = XC
Ref Dly = XP + XO
Int Dly = 0
Measure XS, XP and XO for traveling
equipment (TE), PolaRx4 PRO
Measure XS, XP and XO for remote
equipment (RX), Javed EURO-80
Set up TE and start GPS observation
to get RINEX
Set up RX and start GPS observation
to get RINEX
Calibrate antenna coordinate of TE
from RINEX
Calibrate antenna coordinate of RX
from RINEX
Convert RINEX to CGGTTS using
antenna coord., XS, XP and XO
Convert RINEX to CGGTTS using
antenna coord., XS, XP and XO
Calibrate XS + XR for TE according to
the local standard Z12T
Step 1@TL
Step 2@MSL
Set up TE and start GPS observation
to get RINEX
Calibrate antenna coordinate of TE
from RINEX
Convert RINEX to CGGTTS using
antenna coord. XS, XP, XO and XS + XR
Telecommunication Laboratories
Calibrate XS + XR for RX according to
TE
Discussion
1. The P1 and P2 internal delay are required to be calibrated to
perform calibration by P3 observation
2. If the calibration point is different from UTC, then one should
only measure the delay of these two
3. Overall uncertainty evaluation can refer to the report from
BIPM and EURAMET, who provide very excellent analysis
4. Antenna coordinate is ITRF and calculated from IGS product
5. One can download data and perform data analysis from TL’s
FTP site, ftp://ftp.stdtime.gov.tw
6. Do not hesitate to contact me, Yi-Jiun Huang(TL),
[email protected], if any problems
Thank you for your listening and advice
Telecommunication Laboratories
Calibration Values (incomplete)
1.
2.
3.
TL’s standard: Z12T (last calibration by BIPM @ 2005)
1. X: -2994428.02 m, Y: 4951309.28 m, Z: 2674496.91 m
2. XC = 119.8 ns
3. XP + XO = 52.0 ns
4. XS + XR =
Traveling Equipment: PolaRx4 PRO #965
1. XC = 176.25 ns
2. XP + XO =
3. XS + XR =
Traveling Equipment: PolaRx4 PRO #966
1. XC = 175.38 ns
2. XP + XO =
3. XS + XR =
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BIPM New Calibration Scheme
Motivation:
1. No delay measurement are required
2. The same architecture with conventional scheme
3. Calibrate the remote equipment which is no need to poweroff
4. BIPM expects lower uB (< 2ns) by conducting new calibration
scheme due to no delay measurement
Goal:
1. Perform calibration by BIPM’s new calibration scheme
2. The traveling equipment and remote equipment will be
calibrated w. r. t. local equipment
Telecommunication Laboratories
Total Delay
Telecommunication Laboratories
Ref: Z. Jiang et al, 2011 IFCS-EFTF
Realize the Measurement of UTC(TL) - UTC(MSL)
Use total delay of the link, dX(Z12T,RX), to measure UTC(TL) - UTC(MSL)
GPS
GPS
Local
Ashtech
Z-XII3T
(Z12T)
Remote
RX
X(Z12T)
RINEX to CGGTTS
Cbl Dly = 0
Ref Dly = 0
Int Dly = 0
UTC(TL)
X(RX)
UTC(MSL) RINEX to CGGTTS
Cbl Dly = 0
Ref Dly = 0
Int Dly = 0*
UTC(TL) - UTC(MSL)
= REFGPS(Z12T@TL) - REFGPS(RX@MSL) - dX(Z12T,RX)
Telecommunication Laboratories
Which term should we calibrate?
Telecommunication Laboratories
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New Scheme: Delay Measuremet NOT Required
 X, Total Delay
GPS
Antenna
XS Antenna Delay
XC Cable Delay
GNSS
Receiver
XR Internal Delay
XO Internal Reference Offset
XP 1-PPS Offset
REF
Source
RINEX to CGGTTS
Cbl Dly = 0
Ref Dly = 0
Int Dly = 0
REF - GPS = REFGPS(GNSS Receiver) - (XO + XP) + (XS + XC+ XR)
:= REFGPS(GNSS Receiver) X
Term to be calibrated: total delay of receiver, X
(or total delay of the time link, dX)
Telecommunication Laboratories
Step 1: Calibrate Total Delay Locally
Goal: Calibrate the total delay of the time link, Z12T-P965, dX(Z12T, P965)
Delay measurement and previous calibration results are not required
GPS
GPS
Z12T@TL
P965@TL
X(Z12T)
X(P965)
UTC(TL)
RINEX to CGGTTS
Cbl Dly = 0
Ref Dly = 0
Int Dly = 0
dX(Z12T, P965)
:= X(Z12T) - X(P965)
= REFGPS(Z12T@TL) - REFGPS(P965@TL)
Telecommunication Laboratories
RINEX to CGGTTS
Cbl Dly = 0
Ref Dly = 0
Int Dly = 0*
Step 2: Calibrate Total Delay Remotely
Goal: Calibrate the total delay of time link Z12T-RX, dX(Z12T, RX)
, using calibrated dX(Z12T,P965)
GPS
GPS
P965@MSL
RX@MSL
X(P965)
X(RX)
UTC(MSL)
RINEX to CGGTTS
Cbl Dly = 0
Ref Dly = 0
Int Dly = 0
RINEX to CGGTTS
Cbl Dly = 0
Ref Dly = 0
Int Dly = 0*
dX(Z12T, RX)
= REFGPS(P965@MSL) - REFGPS(RX@MSL) + dX(Z12T, P965)
Telecommunication Laboratories
Measure XS, XP and XO for traveling
equipment (TE), PolaRx4 PRO
Measure XS, XP and XO for remote
equipment (RX), Javed EURO-80
Set up TE and start GPS observation
to get RINEX
Set up RX and start GPS observation
to get RINEX
Calibrate antenna coordinate of TE
from RINEX
Calibrate antenna coordinate of RX
from RINEX
Convert RINEX to CGGTTS using
antenna coord., XS, XP and XO
Convert RINEX to CGGTTS using
antenna coord., XS, XP and XO
Calibrate dX(Z12T, TE) according to
the local standard Z12T
Step 1@TL
Step 2@MSL
Set up TE and start GPS observation
to get RINEX
Calibrate antenna coordinate of TE
from RINEX
Convert RINEX to CGGTTS using
antenna coord. XS, XP, XO and XS + XR
Telecommunication Laboratories
Calibrate dX(Z12T, RX) for RX
according to dX(Z12T, TE)
Calibration Values (incomplete)
1.
Total Delay of the Time Link
1. Link Z12T-P965: dX(Z12T, P965) = 189.2 ns
2. Link Z12T-P965: dX(Z12T, P966) = 192.7 ns
3. Link P965-P966: dX(P965, P966) = 3.5 ns
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