Hybrid Geoid Models in Brazil: Development and Evaluation
20/09/2016 | 16:45 | Session 3: Local/regional geoid determination methods and models
Author(s): Daniel Arana, Paulo De Oliveira Camargo and Gabriel Do Nascimento Guimarães
Daniel Arana, Paulo De Oliveira Camargo and Gabriel Do Nascimento Guimarães
This work aims to develop a hybridization methodology of geoid models, providing models more consistent with the altimetric component from GNSS (Global Navigation Satellite Systems). The study area extends from 26° to 19° South in Latitude and 54° to 44° West in Longitude. This region covers the State of São Paulo and surrounding areas in Brazil. Non-hybrid geoid models such as EGM08 (Earth Gravitational Model 2008) and GEOIDSP2014 (Geoide de São Paulo - 2014) have shown RMS (Root Mean Square) of ± 0.187 and 0.156 m, respectively, in 315 benchmarks from RAFB (Altimetric Fundamental Brazilian Network) tracked by GNSS in the study area. As determination of the altimetric component using GNSS is becoming better known and used for purposes of leveling with the aid of geoid models, more and more effort is being made to improve the consistency of the geoid models. Since model quality degrades heights and limit the application of GNSS, the hybrid geoid models appear showing better consistency thanks to the integration of GNSS data to models. In this study, 315 points were used to generate two hybrid geoid models HYDEGM and HYDGEOIDSP. 90% of the data was used in offset surface generation by linear RBF (Radial Basis Function) artificial neural networks, while 10% of the altimetric points were used for validation of models. Checkpoints indicate that the geoid hybrid models feature RMS ± 0.107 and ± 0.098 m, respectively. The results are promising since they represent an improvement of 40% in consistencies compared with gravimetric geoids, providing users with better quality in transformation of geometric to orthometric heights.