APPLICATION OF A LOCAL LINEAR MODEL IN THE DETERMINATION OF ORTHOMETRIC HEIGHTS REFERRED TO THE BRAZILIAN GEODETIC SYSTEM - DOI 10.5216/bgg.v36i1.40378

Abstract

The use of Global Positioning Satellite Systems (GNSS) allows quick retrieval of relatively accurate ellipsoidal heights (h). However, in engineering applications, it is necessary to determine the corresponding orthometric heights (H) referred to the geoid or Brazilian Geodetic System (BGS), whose references are the Earth’s
gravitational field and average tide gauge located in Imbituba (SC), respectively. The determination of H, in relation to geoid surface, requires gravimetric techniques or the use of global or regional geopotential models. The classic topographic leveling is applied to the BGS, starting from the High-Precision Altimetric Network (HPAN) landmarks up to the location of interest. In such methods, the operations are usually labor-intensive, of high costs and spend much time. This article presents the determination of H referred to BGS through a first-order linear model that was calibrated locally. The methodology consisted in using a set of 17 references level (RL) of HPAN for the model calibration and 7 RL for its validation. The model application was in heights evaluation of two sets of random points, in an urban watershed. It is possible to apply the model in regions with no transition of UTM Zone.
Keywords: GPS, Ellisoidal Height, Watershed.