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Footprint Observations at the Fundamental Station Wettzell
Wolfgang Schlüter
Thomas Klügel
Christian SchadeBundesamt für Kartographie und Geodäsie
Fundamentalstation Wettzell
Germany
Why a Footprint Network?A footprint network consists of geodetic markers in the area
of the geodetic observatory, spread away several km from the observatory (dependant on geological structure of the area itself)
Continuous observations with highest accuracy allow the documentation of the local, geological stability of the observatory site, which is important for the knowledge of e. g. representing station motion the plate motion.
Footprint network is needed in addition to a local survey network, which allows the determination of local ties e.g. between VLBI and GPS reference points
GPS Footprint Network Wettzellpermanent installed GPS receivers: Ashtech Z12
Wettzell (WTZZ)
Arber (ARBR)
Hohenwarth (HOWA)
Prackenbach (PRAC)
Miltach (MILT) 19.0km
7.0
km8.2 km
7.1
km
Local Survey Network
Pillar 21
GPS-Array
RTW
GPS Antenna Array• GPS Array
– WTZR • Turbo Rogue ACT
– WTZA• Ashtech Z12T
– WTZZ• Javad (GPS/GLONASS)
– WTZT• Trimble 4000SSI
– WTZJ• Javad (Real Time)
• WEB Cam– Taking pictures (clouds,
snow,sunshine)
Pillar 21
• Survey Pillar with an integrated AGI 722 borehole tiltmeter, resolution <100nrad)
• GPS Receiver Ashtech Z12 for continuous observations
Pillar 21 - Stability
Analysis Strategy for Daily Solutions
Bernese Software, Version 5.0
RINEX - Raw Data Orbit/EOP - Information
Preprocessing
L3 Ambiguity-Float Solution
Ambiguity Resolution
L3 Ambiguity-Fixed Solution
RecieverClock Cycle
Slips
Widelane/Narrowlane
NEQ Files:Combination
LocalTroposphere
Model
Baselines
RMS-DependentStrategy
Residuals in Height of GPS Array WTZA and WTZR with reference to Pillar 21
Snow
WTZA
WTZR
100d10 mm
SnowSnow
Residuals in North of GPS Array WTZA and WTZR with reference to Pillar 21
WTZA
WTZR
1mm
Residuals in East of GPS Array WTZA and WTZR with reference to Pillar 21
WTZA
WTZR
1mm
Residuals in Height of the Footprint Points with respect to pillar 21
ARBR HOWA
MILT PRAC
Antennachange
10mm
100d
Residuals in North of the Footprint Points with respect to pillar 21
ARBR HOWA
MILT PRAC 2mm100d
Residuals in East of the Footprint Points with respect to pillar 21
ARBR HOWA
MILT PRAC
Conclusion
• Monitoring of stability below 1mm repeatability• Seasonal effects can be detected
– No significant height changes!– Seasonal effect in the North components (1mm amplitude)– Significant seasonal effect in East components (up to 2mm
amplitude)
• Influence of snow on the antenna in winter decrease the monitoring to few millimeter and creates systematic effects
• The area around the FSW is stable!• Is the order of variations in positions transferable to the
20m RTW reference point?