Hacia un nuevo modelo de geoide para la Argentina
Hacia un nuevo modelo de geoide para la Argentina
Fecha: 10-14 de noviembre 2014
Nombre del evento:XXVII Reunión Científica de la Asociación Argentina de Geofísicos y Geodestas
Organización: Asociación Argentina de Geofísicos y Geodestas (AAGG)
Lugar: San Juan
Expositores: Diego Piñón(1)(2)
Coautores: Kefei Zhang(2), Suqin Wu(2), Sergio Cimbaro(1)
Instituciones: (1) Instituto Geográfico Nacional, (2) RMIT University,
Resumen: The main objective of physical geodesy is to study the shape of the Earth, its gravity field and the geoid, which is an equipotential surface that is most close to the sea level. Precise geoid determination has been an important research topic in geodesy and geophysics in the past two decades. Scientists and government agencies all around the world have made great efforts for the development of high-accuracy geoid models. These geoid models are not only designed for scientific applications, but also used for other purposes such as a reference surface for mapping, sea level monitoring and natural resources exploitation and management.
A geoid model is required to define a national height datum. High accuracy geoid models have experienced an unprecedented demand due to the rapid development of GPS/GNSS technologies. Using a geoid model, ellipsoidal heights easily determined from GPS/GNSS observations can be transformed into physical heights, which are associated to the Earth’s gravity field, without the need for expensive and time-consuming spirit-levelling. Physical heights are important for mapping, engineering and civil infrastructure since they indicate the flow direction of fluids, due to the fact that fluids are attracted by the gravity force of the Earth rather than influenced by height differences.
This research aims to investigate robust methodologies for the development of a new and precise geoid for Argentina using all the available gravity observations and the latest global geopotential models (GGMs) along with detailed digital terrain models (DTMs). The new geoid model for Argentina was developed using the remove-compute-restore technique and combining an optimal GGM with approximately 230,000 land and marine gravity observations. Several GGMs (e.g. EGM08, GOCO03S and EIGEN-6C2) were tested for the identification of the best fitting model. Terrain corrections were calculated for all gravity observations using a combination of the SRTM_v4.1 DTM and the SRTM30_Plus bathymetric model. Two terrain correction methods, the classical Hammer chart and prism integration approach, were tested and compared. The results showed that the prism integration method is better in terms of the accuracy of the result and the time consumed in the computation.
The observed Helmert-gravity anomalies were gridded using the inverse square distance weighting method. The world gravity model WGM2012 was utilised to derive gravity data for all the regions that lacked such observations. The final gravity anomaly grid was evaluated in the Stokes’s integral in a convolution form for the determination of the precise geoid using the SPFOUR program from the GRAVSOFT software package. The accuracy of the new geoid was assessed by comparing its geoidal undulations over more than 1,500 GPS heighting benchmarks, which have both orthometric and ellipsoidal heights. Results showed that an accuracy of better than 30 centimetres was achieved by the new geoid model.