Application of ionospheric corrections in the equatorial region for L1 GPS users

Abstract

In the absence of the selective availability, which was turned off on May 1, 2000, the ionosphere can be the largest source of error in GPS positioning and navigation. Its effects on GPS observable cause a code delays and phase advances. The magnitude of this error is affected by the local time of the day, season, solar cycle, geographical location of the receiver and Earth's magnetic field. As it is well known, the ionosphere is the main drawback for high accuracy positioning, when using single frequency receivers, either for point positioning or relative positioning of medium and long baselines. The ionosphere effects were investigated in the determination of point positioning and relative positioning using single frequency data. A model represented by a Fourier series type was implemented and the parameters were estimated from data collected at the active stations of RBMC (Brazilian Network for Continuous Monitoring of GPS satellites). The data input were the pseudorange observables filtered by the carrier phase. Quality control was implemented in order to analyse the adjustment and to validate the significance of the estimated parameters. Experiments were carried out in the equatorial region, using data collected from dual frequency receivers. In order to validate the model, the estimated values were compared with "ground truth". For point and relative positioning of baselines of approximately 100 km, the values of the discrepancies indicated an error reduction better than 80% and 50% respectively, compared to the processing without the ionospheric model. These results give an indication that more research has to be done in order to provide support to the L1 GPS users in the Equatorial region.

Intercomparison of Integrated Water Vapor Estimates from Multisensors in the Amazonian Region

“…The free electrons in the ionosphere affect the propagation of the GPS signal (Leick 1995), generating error that is inversely proportional to the square of the carrier frequency and proportional to the total electron content (TEC) along the path between the satellite and receiver. The TEC is mainly a function of incident solar radiation flux that can vary by a wide range of phenomenon, such as sunspot cycle, the rotation of the sun, the earth's magnetic field, season, and localization (Spilker 1994;Camargo et al 2000). Seeber (1993) describes this relation as a power series of 1/f ( f is carrier frequency), where the higher-order terms are frequently ignored.…”

A new approach to outlying data in estimation of vertical total electron content

“…These are produced to test real-time data acquisition, mapping techniques and monitoring facilities [21,23,24,33]. The VTEC mapping provides accurate ionospheric calibrations for navigation systems.…”

“…TEC can be modelled from the GPS observations. Variations in the TEC depend on the local time of the day, seasons, solar cycle, geographic location of the receiver and earth's magnetic field [20,24]. TEC values can be converted to Vertical Total Electron Content (VTEC) using different mapping function.…”

Análise da ionosfera usando dados de receptores GPS durante um período de alta atividade solar e comparação com dados de Digissondas

“…Como exemplo de serviços gratuitos dessa natureza pode-se citar os mapas de TEC produzidos e disponibilizados regularmente pelo IGS (International GNSS Service ) desde 1998 (Feltens & Schaer, 1998;IGSCB, 2009). No Brasil diversas pesquisas nesta linha já foram desenvolvidas nosúltimos dez anos Fedrizzi, 1999;Camargo et al, 2000;Fonseca Junior, 2002;Matsuoka & Camargo, 2003Rodrigues, 2003;Veronez, 2004;Aguiar & Camargo, 2006, 2007.…”