Transcript Results of the IfE absolute gravity campaigns in 2004

The IfE absolute gravimetry
campaigns 2003, 2004, 2005:
an epilogue
Olga Gitlein, Ludger Timmen
Absolute gravity station distribution
different
FG5’s
institutions
22
8
BKG, FGI, IfE
16
24
4
FGI, IfE, UMB
2005
13
30
4
FGI, IfE, UMB
20032005
25
34
epoch
IfE total
2003
16
2004
Station occupations by IfE in 2003 – 2005
Station
GPS
2003
Ålesund
x
•
Andøya
x
2004
2005
total
Station
GPS
2003
2004
2005
total
•
•
3
1
Arjeplog
x
•
•
1
Borås
x
•
Ås
•
1
Kiruna
x
Bodø
•
1
Kramfors
1
Mårtsbo
x
1
Onsala
x
•
Hønefoss AC
•
1
•
•
2
•
•
3
•
•
2
•
•
•
3
•
Tromsø
x
Trondheim
x
•
1
Östersund
x
•
•
•
3
Trysil AC
x
•
1
Skellefteå
x
•
•
•
3
Cophg./Budd.
x
•
1
Visby AA
x
•
•
2
3
Metsähovi
x
••
••
5
1
Sodankylä
x
•
1
2
Vaasa AA
•
Cophg./Vestv.
Bornholm
Helsingør
•
•
•
x
•
•
Vaasa AB
25 different stations
•
•
1
x
•
•
•
3
∑
16
16
13
47
Comparison of 2004 and 2005 results
Absolute gravity difference 2005 – 2004
[µGal]
MIN
MAX
MEAN
RMS
-4.2
1.8
-0.8
±1.9
Absolute gravity results in
2005 are less than in 2004
at nearly all 13 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
Instrumental precision
• gravity difference at ~120 cm sensor
height from absolute and relative
gravity measurements between two
pillars at Metsähovi, Onsala and
Bad Homburg
Bad
Metsähovi Onsala
Homburg
AB-AC
AS-AN
BA-AA
dg(rel)
±0.5 µGal
7.7
34.9
Difference dg(abs) – dg(rel)
[µGal]
Onsala
1.9
1.9
-1.6
2.7
1.9
0.2
1.4
1.1
-2.6
0.1
1.7
±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