Analysis of the residuals in the calculation of speeds geocentrics from daily time series PPP

Abstract

The online processing of GNSS observations has been increasing in recent years. Different services such as the one offered by the Canadian Space Reference System (CSRS), under the Precise Point Positioning (PPP) modality, offers the possibility of knowing in a fast and effective way the three-dimensional position from a rinex file. Taking advantage of these results, daily files were processed for a period of 2.5 years and for 10 GNSS stations in Costa Rica which are integrated into the Sistema de Referencia Geocéntrico para las Américas (SIRGAS). The geocentric coordinates derived from the on-line PPP processing were considered as observation vectors for the estimation of their velocities (Moya et al, 2017). However, a statistical test called the outliers test (Pelzer, 1985) was previously programmed and implemented for the estimation of potential atypical observations. This test is frequently used in the analysis of geodetic networks (Knight et al, 2010), however, it was now applied in the linear velocity calculation model. The adjustment process for the calculation of velocities was done iteratively per station and per coordinate, excluding the outlier observations marked by the test in each process. On average, this test detected a series of observations with residuals ranging from -50 mm to 40 mm in its three components. Finally, with the purified velocities of oitliers, they were validated with respect to the SIRGAS multiannual solution SIR15P01, taking as reference time 2017.0. The average differences between the two determinations were _15 mm.