Abstract
This paper deals with the geopotential approach to investigate the present Brazilian Height System (BHS). Geopotential numbers are derived from Global Positioning System (GPS) satellite surveying and disturbing potential on selected benchmarks. A model for the disturbing potential can be obtained by an existing set of spherical harmonic coefficients such as the Earth Gravity Model 2008 (EGM08). The approach provides absolute evaluation of local normal geopotential numbers (aka spheropotential numbers) related to a so-called World Height System (WHS). To test the validity of the proposed methodology, a numerical experiment was carried out related to a test region in Southern Brazil. The accuracy of the derived geopotential numbers was tested versus local normal geopotential numbers based on 262 GPS/leveling points. The root mean square error (RMSE) value for metric offset of BHS derived from geopotential numbers and the disturbing potential modeling in the test area was estimated to be near 0.224 meters in the absolute view. Therefore, since these spheropotential numbers are referred to a local datum, these results of comparisons may be an indicator of the mean bias of local network due to the effect of local Sea Surface Topography (SSTop) and possible offset between the unknown reference for the BHS and the quasigeoid model in the region.
Highlights
The heights of the Brazilian Height System (BHS) were obtained by using spirit leveling as static system, and reduced for the gravity effect only by the normal gravity field
In the sequence we describe the data and the computation methods used to calculate the potential difference between the BHS and the World Height System (WHS)
SUMMARY AND CONCLUSIONS The Brazilian Height System (BHS) is defined as a normal-orthometric height system, this means that the difference between the ellipsoidal heights and normalorthometric heights provides η as showed in (13)
Summary
The heights of the Brazilian Height System (BHS) were obtained by using spirit leveling as static system, and reduced for the gravity effect only by the normal gravity field. The normal-orthometric heights are not capable of supporting the physical height determination departing from ellipsoidal heights obtained with Global Navigation Satellite System (GNSS) technologies (e.g., Global Positioning System – GPS). It is well-know that the height determination using GNSS is based in a simple operative relation that links GNSS’s geodetic height, h , above a given ellipsoid and the orthometric height, H O. These heights are counted along the Ferreira, V.
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