Regional ionospheric model applied to Global Positioning System

Abstract

The positioning of points with the GPS system has become an important tool used in many different areas of knowledge. However, in some situations, the demand for great accuracies has caused the inconvenience of high cost when dual frequency receptors are purchased. Even with technological advances, the ionosphere is one of the error sources that affect the positioning of points. For users that have dual frequency equipments, this error is modeled with great efficiency through the processing of data with iono free solution. In Brazil, most users have equipments that gather information from the C/A code only, and/or from the C/A code and carrier L1. In this case, a few models are used, like the Klobuchar’s for example, with error reduction for absolute positioning of 50%, approximately. For relative positioning, with bases further than 20 km, the use of this model is not the most appropriate. In this context, this work consists in the development of a method that can model the ionospherical delay with a second degree polynomial, based on sequential adjustment of observations. The necessary information for this modeling was taken from GPS stations of the Brazilian Network for Continuous Monitoring - RBMC. Evenly, with Single Point Positioning, it has been proved that the offered model has lead to a positional error reduction of near 65% if compared to the processing without the use of any ionospherical model.

Key words: Regional model, ionosphere, sequential adjustment, GPS.