The official Brazilian geoid model, called MAPGEO2015, was computed as a cooperation between IBGE and EPUSP. It is a 5' x 5' grid of geoidal undulations referred to SIRGAS2000, covering the area from 35° S to 6° N in latitude and from 75° W to 30° W in longitude. The dataset consists of 947,953 terrestrial gravity points (450,589 in Brazil), a digital terrain model based on SRTM and the EIGEN-6C4 global geopotential model up to degree and order 200. The remove-compute-restore procedure was used, where the short wavelength components were computed by Stokes integration via Fast Fourier Transform technique. In areas where sufficient data were available, neural network technique was used to complete the gravity anomaly information. Through the values of normal-orthometric heights of 592 geometric levelling points (RRNN) of the Brazilian High Precision Altimetric Network, it was possible to evaluate the consistency of the geoid undulation model, observing an improvement of approximately 20% compared to the version published in 2010. In particular, the differences between MAPGEO2015 undulations and GNSS/levelling observations show an RMS of 17 cm.
The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination.