VALIDATION OF THE DIGITAL ELEVATION MODEL (SRTM) WITH GNSS SURVEYING APPLIED TO THE MIRIM LAGOON HYDROGRAPHIC BASIN

Fernando Comerlato Scottá,Iran Carlos Stalliviere Corrêa,Andrea Lopes Iescheck,Ricardo Augusto Lengler Franchini,Patricia Andréia Paiola Scalco,Rafael Mastracusa De Oliveira

doi:10.1590/s1982-21702018000300026

Fernando Comerlato Scottá, Iran Carlos Stalliviere Corrêa + Show 4 more

Open Access

https://doi.org/10.1590/s1982-21702018000300026

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Abstract

Abstract Between 2013 and 2014, a kinematic positioning based on the Global Navigation Satellite System (GNSS) was carried out for this research work. This GNSS survey resulted in 275916 points with tridimensional coordinates in the cross-border basin area of 58205 km2 called Mirim Lagoon Hydrographic Basin, located in south of Rio Grande do Sul (Brazil) and west of Uruguay. This study aims at showing the methodology firstly and, furthermore, results regarding the validation of the vertical accuracy of the DEM SRTM through kinematic positioning by GNSS, in the Mirim Lagoon Hydrographic Basin region. Also, the GNSS surveying data was post-processed with the Precise Point Positioning (PPP) method, and the ellipsoidal height was converted into orthometric height through the software INTPT geoid. During this study, the geopotential model (EGM96) was used to transform altitude differences between two countries, Brazil and Uruguay. Results showed that the vertical mean absolute error of the DEM SRTM vary from 0.07 m to ± 9.9m with average of -0.28m. This vertical accuracy is better than the absolute vertical accuracy value of ±16m published in the SRTM data specification and validates the DEM SRTM.

Highlights

The Shuttle Radar Topography Mission (SRTM) (Rabus et al 2003 and Van Zyl 2001) results from a collaborative effort among the National Aeronautics and Space Administration (NASA), the National Geospatial-Intelligence Agency (NGA), the U.S Department of Defense (DoD), the German spatial agency (Deutsches Zentrum für Luft und Raumfahrt - DLG) and the Italian spatial agency (Agenzia Spaziale Italiana - ASI)
The results confirm that the vertical accuracy of Global Navigation Satellite System (GNSS) survey observations is suitable to validate digital elevation model (DEM) SRTM
Figure 7 shows the orthometric heights resulting from the GNSS surveying and the orthometric heights of the DEM SRTM, from the samples N=275,916, N=4000 and N=500 points

Summary

Introduction

The objective was to map the Earths relief using Interferometric Synthetic Aperture Radar (InSAR) technology system. 2000, the SRTM released for the first time a global digital elevation model (DEM) with high-quality resolution levels of one and three arcseconds (approximately 30m and 90 m). For DEM SRTM development, in the Mirim Lagoon Hydrographic Basin, SRTM images were used in version 3, band C, with a spatial resolution of 1 arcsecond, roughly 30m. This relief information was processed and distributed by the U.S Geological Survey – USGS (http://earthexplorer.usgs.gov/). The SRTM project aimed to collect near-global topographic data with absolute horizontal and vertical accuracies better than 20 and 16 m, respectively, with 90% confidence (Rabus et al 2003 and JPL 2009)

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