A localização geográfica de plataformas no Sistema Brasileiro de Coleta de Dados Ambientais

This paper presents the work being done in the Brazilian Environmental Data Collection System related to the location determination of mobile applications, such as animal tracking, vessel monitoring, drift buoys tracking and moored buoys monitoring. The geographical location of the platform is computed based on Doppler shift measurements at a receiving station. A version of the location software was developed and it is being tested with fixed platforms and with some initial trials with mobile platforms. For the evaluation with the fixed platforms, two platforms were selected: DCP 113 located in French Guiana (5,1417°N; 56,0600°W) and DCP 32590 located in Cuiabá (15.555008°S; 56,06976°W) . The results of location are compared using two different satellites SCD-2 (25 degrees inclination) and NOAA17 (polar orbit) during 8 days period, starting on October 30 to November 7, 2008. The Geographical Location Software uses the Two Line Elements (TLE) as a standard form to feed the satellite orbit and the Doppler measurement files capture during a satellite pass over a receiving station related to the specific platform to be located. The error results of the Location Software are compared between the two satellites, SCD-2 and NOAA-17. The location error depends on the geometry between the platform location, the receiving station location and the satellite pass. It also depends on the quality of the platform transmitter (oscillator stability, transmitted power), the on board oscillator, and the quality of frequency and time measurements at the station.