the ife absolute gravimetry campaigns 2003, 2004, 2005: an epilogue
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The IfE absolute gravimetry campaigns 2003, 2004, 2005:
an epilogue
Olga Gitlein, Ludger Timmen
epoch IfE total different FG5’s institutions
2003 16 22 8 BKG, FGI, IfE
2004 16 24 4 FGI, IfE, UMB
2005 13 30 4 FGI, IfE, UMB
2003-2005 25 34
Absolute gravity station distribution
Station GPS 2003
2004
2005
total
Ålesund x • 1
Andøya x • 1
Ås • 1
Bodø • 1
Hønefoss AC • 1
Tromsø x • 1
Trondheim x • 1
Trysil AC x • 1
Cophg./Budd. x • 1
Cophg./Vestv. • • • 3
Bornholm x • 1
Helsingør • • 2
Station GPS 2003
2004
2005
total
Arjeplog x • • • 3
Borås x • 1
Kiruna x • • 2
Kramfors • • • 3
Mårtsbo x • • 2
Onsala x • • • 3
Östersund x • • • 3
Skellefteå x • • • 3
Visby AA x • • 2
Metsähovi x • • • • • 5
Sodankylä x • 1
Vaasa AA • 1
Vaasa AB x • • • 3
∑ 16 16 13 47
Station occupations by IfE in 2003 – 2005
25 different stations
differences due to:• Uplift signal• measurement uncertainty• Local and regional groundwater• residual air mass effect• Soil moisture• Wind driven sea and ocean water flow
[µGal]
MIN MAX MEAN RMS
-4.2 1.8 -0.8 ±1.9
Comparison of 2004 and 2005 results
Absolute gravity results in 2005 are less than in 2004
at nearly all 13 stations.
Absolute gravity difference 2005 – 2004
• gravity difference at ~120 cm sensor height from absolute and relative gravity measurements between two pillars at Metsähovi, Onsala and Bad Homburg
Instrumental precision
MetsähoviAB-AC
OnsalaAS-AN
Bad HomburgBA-AA
dg(rel)±0.5 µGal
1.9 7.7 34.9
Difference dg(abs) – dg(rel)
[µGal]
1.9 1.4 -2.6-1.6 1.1 0.1 2.7 1.7 1.9 0.2Onsala
±1…±2 µGal several setups to minimize the instumental uncertainties(Floor-recoil, azimuth (Coriolis/attrition), setup,…)
Summary of IfE campaigns 2003 – 2005
• 25 different stations occupied by IfE
• accuracy for one station determination ±2…±4 µGal
• several FG5 setups per station
• relative gravimetry: vertical gradients (<±1 µGal)
eccentres (national net
points)
• monitoring of lokal water level (groundwater, lakes)
• monitoring of height changes of absolute gravity point
levelling to height benchmarks
• at nearly all stations continuous GPS available
• connection to tide gauges
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