lambert wanninger, stephan wallstab-freitag
DESCRIPTION
Combined Processing of GPS, GLONASS, and SBAS Code Phase and Carrier Phase Measurements. Lambert Wanninger, Stephan Wallstab-Freitag Geodetic Institute, Dresden University of Technology, Germany. ION GNSS 2007, Session D2. - PowerPoint PPT PresentationTRANSCRIPT
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.