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The Geodesy Subcommitee of the National Committee of IUGG created the working group "Geopotential Origin" in December 2000 in order to coordinate the national activities, establish and set down a new Vertical Reference System and to interact with Group III of SIRGAS (Geocentric Reference System for the Americas) Project. For that, all the activities were organised in four items. This contribution describes the main results obtained in each of them as well as future tasks for the near future: Tide Gauges: The origin of the Argentine Vertical Reference System, defined by means of tide gauge records, is affected by the sea surface topography at the gauge locations. A project to observe and model the sea level variations using both, tide gauges and satellite altimetry, is being carried out since 1998. Four permanently observing GPS stations have already been installed close to gauges along the Argentine Atlantic coast and integrated in the International GPS Tide Gauge (TIGA) Monitoring Project.Geopotential Numbers: All first order levelling network unadjusted height differences were migrated to digital media and merged with the benchmark positions and gravity values. The resulting database consists of 16,000 level differences distributed along about 3,170 lines. Gravity values are missing for 20 percent of the benchmarks. The data set is currently being checked for consistency.Linking of Altimetric Networks from Neighbour Countries: During 2002 the first link between the altimetric networks of Chile and Argentina was done. The result was a difference of 22 cm, the higher value corresponding to Argentine levelling lines. The border point, where the levelling lines of both countries are connected, is Puesto Monte Aymond, near Estrecho de Magallanes in the south extreme of South America. The corresponding activities in order to make two or three new comparisons along the 5,000 km long borderline between these countries are being coordinated.Recently, the determination of a natural water surface (Fagnano Lake) was used like an equipotential surface to connect the altimetric networks of Chile and Argentina where the classical spirit levelling is not accessible due to the lack of roads.Compensation of Height and Gravity Networks: Adjustment of the national gravity and altimetric networks and their linking with the nets of neighbouring countries are in progress, including both new absolute and relative gravity determinations, which are necessary for the adjustment and optimisation processes. [ABSTRACT FROM AUTHOR]

This paper presents a new gravimetric geoid model for Argentina. The methodology applied for its computation as well as the most recent evaluated data are discussed. Argentina is bounded to the west by the highest mountain range in America, the Andes, so different topographic reduction methods are crucial in practical gravimetric geoid determination. To the east, Argentina borders on the Atlantic Ocean so the combination of shipborne gravity data and altimetry derived free-air gravity anomalies was also taken into account. The remove-compute-restore technique was adopted for the geoid determination and the contribution of the local data to the geoid was computed by FFT. As an external evaluation, the gravimetric geoid was compared with geoid undulations of 539 GPS/levelling points available for the country. The importance of this new gravimetric geoid lies in the fact that it will be the official gravimetric geoid for the country, and thus it will be of interest to the entire scientific community utilizing geospatial data. [ABSTRACT FROM AUTHOR]