HR: 0800h
AN: G21A-1256    [Abstracts]
TI: A new strapdown system for moving gravimetry
AU: * Cali, J
EM: jose.cali@esgt.cnam.fr
AF: ESGT, 1, bd Pythagore, Le Mans, 72000 France
AU: De Saint Jean, B
EM: desaintjean@ensg.ign.fr
AF: IGN-LAREG, 6/8 av. Blaise Pascal Champs sur Marne, Marne la Vallee, 77455 France
AU: Duquenne, H
EM: Henri.Duquenne@ensg.ign.fr
AF: IGN-LAREG, 6/8 av. Blaise Pascal Champs sur Marne, Marne la Vallee, 77455 France
AU: Verdun, J
EM: Jerome.Verdun@ensg.ign.fr
AF: IGN-LAREG, 6/8 av. Blaise Pascal Champs sur Marne, Marne la Vallee, 77455 France
AU: Melachroinos, S
EM: stavros@pontos.cst.cnes.fr
AF: CNES, 18, av. E. Belin, Toulouse, 31401 France
AU: Barriot, J
EM: jean-pierre.barriot@cnes.fr
AF: CNES, 18, av. E. Belin, Toulouse, 31401 France
AB: This paper will describe the results of development carried out from our strapdown system for measurements of the gravity field developed in cooperation by the following French organisations: ESGT, IGN, BGI and SHOM. The objective of the research is to realise gravity measurements from an efficient, low cost system with mGal accuracy for spatial resolutions of a small number of kms. The system is based on the combination of 3 high precision accelerometers; a Honeywell QFlex QA-3100-020 - the sensitive axes are not parallel - and an Ashtech ADU2 GPS unit for position and attitude determination based on differential carrier phase measurements between four antennae. The analogue signal proportional to the acceleration experienced by the proof mass of the sensor is digitalized with a 24 bit converter. To take into account the temperature variations of the bias and scale factor the internal temperature sensor is also recorded. We will describe the calibration procedure of the accelerometer which permits an accuracy of a few mGal. We will particularly focus on any impacting phenomena such as temperature or misalignment of the sensitive axis. The inertial acceleration is derived from the GPS position. Because acceleration and GPS measurements are not located at the same point, the signals coming from the accelerometers have to be corrected for the lever arm effect. The complete equation of movement indicates that the correction of level arm effects depends not only on lever arm length but also on vehicle movement parameters. Simulations and real measurements suggest that some of 8 level arm effects have to be taken into consideration in order to achieve accuracy on gravity to within a few milligals. We discuss the various suitable methods for processing gravity with the system with respect to the type of vehicle used to carry out gravity measurements. An application to conduct real life testing on board a vessel will be made in mid October- November, during the oceanographic campaign hosted by the SHOM in the Mediterranean Sea. The goal of this campaign will be to evaluate the accuracy of the surveying methodology, to improve our strapdown system and to validate the numerical treatment. We would like to discuss all of these concerns.
DE: 1200 GEODESY AND GRAVITY
DE: 1294 Instruments and techniques
DE: 1295 Integrations of techniques
SC: Geodesy [G]
MN: Fall Meeting 2005