DGPS positional improvement by mitigating the ionospheric horizontal gradient using GPSurvey

The ionospheric horizontal gradient is the variation of electron density with latitude and longitude which can cause the azimuthal deviation of the Global Positioning System (GPS) ray path. In this paper, the improvement in Differential GPS (DGPS) positioning will be shown by applying the ionospheric horizontal gradient correction to the carrier phase measurement from each GPS satellite. The ionospheric horizontal gradient factor was obtained from ionospheric tomographic images or contour of Total Electron Content (TEC) from Rutherford Appleton Laboratory (RAL) in the United Kingdom (UK). Then, by using an approximate equation, the value of the inospheric horizontal gradient will be obtained, which will be termed as the correction factors. These correction factors then will be applied to the carrier phase measurement from GPS observation data. The positional improvement will be shown using the GPSurvey.