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9 pages, 11 figures, 1 table.-- Available online Nov 7, 2001., An improved model of geomagnetic secular change for the Antarctic was developed using observatory annual mean values measured in Antarctica during the last 40 years. Spherical cap harmonic analysis (SCHA) with a power series time dependence was used to model spatial and temporal variations of main field differences at spatial wavelengths from 3000 to 13,000 km. The model was designed to facilitate merging satellite, airborne, marine and terrestrial magnetic data sets recorded at very different epochs in the Antarctic where significant annual geomagnetic changes have occurred. It improves the fit to observatory data by up to about 50% relative to the International Geomagnetic Reference Field., This research was partially funded by the Italian Programma Nazionale di Ricerche in Antartide (PNRA) and by the Spanish Programa Nacional de Investigación en la Antártida (PNIA, CICYT, Project No. ANT98-0886).

11 pages, 6 figures., A permanent geomagnetic observatory is always the ideal reference station for monitoring geomagnetic activity during airborne, marine or ground magnetic surveying, especially in Antarctica, where logistic difficulties are an important factor even for the deployment of temporary base stations. The utility of the magnetic observatory records for the correct reduction of the survey data is reinforced if both their spatial homogeneity and their particular anomaly biases are assessed. This, combined with data from the magnetic surveys themselves, can yield information on the crustal contribution to the Earth's magnetic field from a remote and poorly understood region. With these objectives in mind, we present a new geomagnetic observatory in the South Shetland Islands, where (because of the complex regional tectonic characteristics) magnetic surveys on one or another structure are conducted from time to time. An evaluation of the observatory representativeness and a look at the crustal magnetic anomaly ambience are also given., This work is part of the Research Project ANT95-0994-C03, supported by the Spanish Comisión Interministerial de Ciencia y Tecnología.