Análise da correção do erro ionosférico em receptores GPS de frequência simples a partir da implementação do algoritmo de Klobuchar em Python

Abstract

The Selective Availability (SA) technique was deactivated on May 2, 2000, since then the biggest source of errors in positioning with the Global Positioning System (GPS) has come to be related to the ionosphere. The ionospheric error is directly proportional to the total electron content (TEC) present along the path taken by the signal in the ionosphere. TEC undergoes variations in time and space and is influenced by several variables such as: solar cycle, time of year, time of day, geographic location and geomagnetic activity. In simple frequency systems, the correction of these errors is associated with the use of an ionospheric model that estimates the amount of TEC present in the ionospheric layer and the evaluation of these models is done by analyzing the post-processed results of the applied corrections. In this work were evaluated: IONEX files of corrections from the Global Ionosphere Maps (GIM) service generated by the International GNSS Service (IGS) and the response to the Klobuchar algorithm designed by the GNSS application package RTKLib. To validate RTKLib’s response to IONEX files, maps were generated from the implementation of the Klobuchar algorithm in Python and as a basis of comparison, double frequency correction was used, since it corrects about 99% of errors associated with the ionosphere . The post-processing method applied by RTKLib proved to be effective, returning the expected values, so the IGS maps were more accurate than the correction applied by the Klobuchar method, justifying its use by the scientific community as a basis for comparison in error correction in single frequency GPS receivers.