Quality Control on Outliers Removal for Improvement of Estimation of Hardware delay of GNSS Receivers

Abstract

With the scope of space technologies, their applications have been increasingly used in society based on the need to accurately position them using the GNSS (Global Navigation Satellite System). Considering that the ionospheric refraction is one of the main sources of error in GNSS, its correct modeling is extremely important to carry out the positioning. The error due to this refraction in GNSS signals is proportional to the TEC (Total Electron Content). However, to calculate the TEC from the GNSS observables, it is necessary to use the values ​​of the instrumental trend effect of the satellite and the receiver. This effect is the result of the delays that the GNSS signal undergoes when traveling through the satellite and receiver hardware. The estimation of instrumental effects as well as its proper correction in ionospheric delay has already been applied and has proven to be effective, studies where the ionospheric error is analyzed without the estimation of the instrumental tendency of the receiver and compared with ionospheric error corrected for this tendency, show that the correction of these values ​​resulted in a difference between stations in the place of decimeters where it was metric before. However, there is still a need to investigate the presence of outliers in these implemented models. That said, the main objective of this research is to carry out the application of quality control through the Data Snooping method on the ionospheric observables obtained through the PPP with ambiguity resolution, aiming to improve the estimation of the instrumental tendency values ​​of the receiver and, consequently, the quality of positioning and user-level GNSS navigation.