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?