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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.

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Presentation Transcript
slide1

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

gps glonass sbas
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
orbit accuracy gps glonass
Orbit Accuracy GPS/GLONASS

Broadcast

orbit accuracy

(source: JPL, IGS)

Precise IGS orbits

GPS (final): <5 cm

GLONASS: 15 cm

observation quality gps glonass
Observation Quality GPS/GLONASS

Code Observations: Elevation dependence of MP1

Station 1 / Receiver 1

Station 2 / Receiver 2

Proper weighting required  receiver dependence

gps glonass sbas1
GPS+GLONASS+SBAS

Observation Equations for

Single-Difference Carrier Phases

GLONASS inter-channel bias difference [cm]:

glonass inter channel bias diff
GLONASS Inter-channel Bias Diff.

Double-Difference Residuals L1

GPS

GLONASS

GLONASS

GLONASS

inter-channel

biases removed

glonass inter channel bias diff1
GLONASS Inter-channel Bias Diff.

Long-term Stability

L0 – iono.-free linear combination

glonass inter channel bias diff2
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 diff3
GLONASS Inter-channel Bias Diff.

A priori values of [cm]

baseline results gps glonass
Baseline Results GPS/GLONASS

RTK-like processing:

short baseline, 2 minutes of observations

slide11
SBAS
  • Code and carrier phase
  • observations to
  • GEO satellites
  • presently
  • 10 SBAS satellites,
  • 4 over Europe,
  • just single-frequency
  • EGNOS
  • presently:
  • poor broadcast orbits+clocks
  •  short baselines only
observation quality gps sbas
Observation Quality GPS/SBAS

Code observations:

elevation dependence

of MP1

dual-frequency GPS MP1

single-frequency GPS MP1´

single-frequency SBAS MP1´

slide13
SBAS

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
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
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.
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