Lambert Wanninger, Stephan Wallstab- Freitag Geodetic Institute, Dresden University of Technology, Germany ION GNSS 2007, Session D2 Combined Processing of GPS, GLONASS, and SBAS Code Phase and Carrier Phase Measurements
Feb 02, 2016
Lambert Wanninger, Stephan Wallstab-Freitag
Geodetic Institute, Dresden University of Technology, Germany
ION GNSS 2007, Session D2
Combined Processing of GPS, GLONASS, and SBAS
Code Phase and Carrier Phase Measurements
GPS+GLONASS+SBAS
Maxim: The more satellites the better.
but several differences:• reference systems (GLONASS) transformation• orbit accuracy (GLONASS, SBAS) weighting• observation quality (GLONASS, SBAS) weighting• inter-channel biases (GLONASS) algorithm, estimation
GPS
(30)
GPS+GLONASS
(30+11)
GPS+SBAS(30+4)
GPS+GLONASS+SBAS
(30+11+4)
# visible SV 8.4 11.7 12.4 15.7
PDOP 1.9 1.7 1.6 1.4
Orbit Accuracy GPS/GLONASS
Broadcast orbit accuracy(source: JPL, IGS)
Precise IGS orbitsGPS (final): <5 cmGLONASS: 15 cm
Observation Quality GPS/GLONASS
Code Observations: Elevation dependence of MP1
Proper weighting required receiver dependence
Station 1 / Receiver 1 Station 2 / Receiver 2
GPS+GLONASS+SBAS
Observation Equations forSingle-Difference Carrier Phases
iba
Glonassba
iGlonassba
iba
iGlonassba
iba
SBASGPSba
iba
iSBASGPSba
NhktcR
NtcR
,,,0,,
,
,/
,0,,/
,
GLONASS inter-channel bias difference [cm]: Glonasshc 0
GLONASS Inter-channel Bias Diff.
Double-Difference Residuals L1
GPS GLONASS GLONASS GLONASS inter-channel
biases removed
GLONASS Inter-channel Bias Diff.
Long-term Stability
L0 – iono.-free linear combination
GLONASS Inter-channel Bias Diff.
Temperature effects
Chilling: 20° Celsius temperature difference
no effect
but change of antenna affects inter-channel bias difference
L0 – iono.-free linear combination
GLONASS Inter-channel Bias Diff.
A priori values of [cm]
AshtechZ-18
JPS Legacy,TPS E_GGD,TPS Net-G3
Leica GRX 1200 GG PRO
TrimbleNetR5
Ashtech Z-18 0.0 0.0 2.4 -0.7
JPS Legacy,TPS E_GGD,TPS Net-G3
0.0 0.0 2.4 -0.7
Leica GRX1200 GG PRO -2.4 -2.4 0.0 -3.1
Trimble NetR5 0.7 0.7 3.1 0.0
Glonasshc 0
Baseline Results GPS/GLONASS
RTK-like processing: short baseline, 2 minutes of observations
GPS GPS + GLONASS
average # of SV 8.0 11.6
Combined Float/DGNSSStd. Dev. N/E/Up [cm] 18 / 20 / 25 15 / 19 / 20
Fixed solution# valid solutions (of 360)Std. Dev. N/E/Up [cm]
3580.54 / 0.49 / 1.00
3590.53 / 0.48 / 0.93
SBAS
Code and carrier phase observations to GEO satellites
presently• 10 SBAS satellites,• 4 over Europe,• just single-frequency
EGNOSpresently: poor broadcast orbits+clocks short baselines only
Observation Quality GPS/SBAS
Code observations: elevation dependence of MP1
dual-frequency GPS MP1
single-frequency GPS MP1´
single-frequency SBAS MP1´
SBAS
GPS GPS + SBAS
average # of SV 8.7 12.7
Combined Float/DGNSSStd. Dev. N/E/Up [cm] 16/18/22 15/17/21
Fixed# valid solutions (of 720)Std. Dev. N/E/Up [cm]
7130.44 / 0.35 / 0.89
7120.27 / 0.26 / 0.74
RTK-like processing: short baseline, 2 minutes of observations,dual-freq. GPS, single-freq. SBAS
single-frequency SBAS improves dual-frequency GPS
SBAS Carrier Phase Multipath
Double-difference residuals L1: short static baseline, 2 SBAS satellites
daily multipath pattern, but also changes in pattern:due to daily repetition of orbits, orbit maneuvers
Summary + Outlook
GLONASS• lower orbit accuracy• some receivers: lower accuracy of code observations• inter-channel biases
SBAS• presently + EGNOS only: very poor orbit accuracy • lower accuracy of code observations• single-frequency only
Bright future • GPS L5, dual-frequency SBAS• more GPS/GLONASS/SBAS satellites• Galileo / Compass / GLONASS CDMA
A bird in the hand is worth two in the bush.