Improved geoid models for the state of São Paulo using the SHGeo package

Abstract

Abstract The objective of this paper is to present the effort to establish the geoidal model for the state of São Paulo to be used for mapping purposes by the Instituto Geográfico e Cartográfico do Estado de São Paulo (IGC). This model is limited by 26ºS and 19ºS latitude and 54ºW and 44ºW longitude. The Stokes-Helmert geoid software (SHGeo) from the University of New Brunswick (UNB), Canada, was used. This is well established, tested scientific package for gravimetric geoid determination based on the Stokes-Helmert approach. The gravimetric geoid computation and result validation in the area was facilitated by the utilisation of the following data sets: terrestrial gravimetric data; XGM2019e geopotential model with degrees 100 and 360 to compute the long- and medium-wave components of the gravity anomaly; the UNB_TopoDensT_2v02 global laterally varying topographic density model developed by UNB; and SRTMv3 DEM data. The latter was used to compute topographic effects and downward continuation. The short-wavelength component was estimated using the Fast Fourier Transform (FFT) method, with the Kernel modification proposed by Vaníček and Kleusberg. The quasigeoid models were also calculated using the relationship between geoidal height and height anomaly. The validation of these two models was achieved through the utilisation of GNSS/levelling points (IBGE and IGC), with the geopotential model employed up to degree 100 and 360. In this analysis, the standard deviations of these models were 13 cm and 10 cm, respectively.