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