DIGITAL ELEVATION MODEL FROM RTK GNSS DATA IN THE PIRATINI RIVER FLOODPLAIN IN PEDRO OSÓRIO AND CERRITO

Abstract

This study presents the development of a high-precision Digital Elevation Model (DEM) for the floodplain of the Piratini River, covering the urban areas of the municipalities of Pedro Osório and Cerrito (RS), Brazil. The topographic survey was conducted using an Emlid Reach RS2 GNSS RTK receiver, totaling 2,921 points collected between February and August 2024. The data were processed in ArcGIS Pro 3.5.3 using the Ordinary Kriging geostatistical method, which yielded a mean error of 0.01 meters and a root mean square error (RMSE) of 0.61 meters in cross-validation. The resulting DEM, adopting a spherical semivariogram model with a spatial resolution of 5 m, was made available in two versions—normal altitude and local reference altitude, the latter being adjusted to match the hydrometric gauges of ANA (Brazilian National Water and Sanitation Agency). The study highlights the potential of GNSS RTK surveys at the urban scale to complement globally available DEMs such as SRTM, ASTER, and NASADEM, especially in flat and urbanized areas near watercourses, improving terrain representation and reducing uncertainties in various hydrological applications, such as flood susceptibility analysis, hydrodynamic modeling, and enhancement of flood forecasting and early warning systems operated by the NIP/UFPel.