Evaluation of the altimetry from SRTM-3 and planimetry from high-resolution PALSAR FBD data for semi-detailed topographic mapping in the Amazon Region

Thiago G Rodrigues,Cleber G Oliveira,Waldir R Paradella

doi:10.1590/s0001-37652011000300014

Abstract

The Brazilian Amazon has a deficit of 35% of coverage regarding topographic mapping at semi-detailed (1:100,000) scale. This paper presents an alternative to overcome this scenario using a combination of planialtimetric information from two orbital SAR (Synthetic Aperture Radar) missions. The altimetry was acquired from Shuttle Radar Topography Mission (SRTM), while the planimetry was provided from Fine Beam Dual (FBD) images of the Phased Array L-band Synthetic Aperture Radar (PALSAR) sensor. The research was carried out in the mountainous area of the Serra dos Carajás (Pará State), located on the Amazon region. The quality of the orbital topographic information was evaluated regarding precise planialtimetric measurements acquired from Global Positioning System (GPS) field campaigns. The evaluations were performed following two approaches: (1) the use of Root Mean Square Error (RMSE) and (2) tendency and precision hypothesis tests. The investigation has shown that the planialtimetric quality of the orbital products fulfilled the Brazilian Map Accuracy Standards requirements for 1:100,000 A Class map. Thus, the use of combination of information provided by PALSAR and SRTM-3 data can be considered a promising alternative for production and update of semi-detailed topographic mapping in similar environments of the Amazon region, where topographic information is lacking or presents low quality.

Highlights

Due to the adverse environmental condition, difficult access and large size, the topographic knowledge of the Brazilian Amazon is still poor in some scales
A total of 30 Independent Check Points (ICPs) was selected for the planialtimetric evaluation of the Shuttle Radar Topography Mission (SRTM)-3 Digital Surface Model (DSM) (Fig. 6)
Distinct causes can be considered to explain the observed bias, including: the inherent relative characteristic of the SRTM-3 DSM, since the phase return in C-band was influenced by the attributes of the rainforest (Farr et al 2007); influence of topographic aspect, which was attributed to the effect of incidence angle of the SAR used to produce the interferometric DSM (Jarvis et al 2004), and the poor spatial resolution (90 m) that could be significant in steeper slopes

Summary

Introduction

Due to the adverse environmental condition (rain, cloud and dense vegetation), difficult access and large size (almost 5,500,000 km of the national territory), the topographic knowledge of the Brazilian Amazon is still poor in some scales. The available information for the remainder of the region was mainly produced in the time-frame of 1960 and 1980, and needs to be up-dated or re-mapped. The usage of airphoto based on photogrammetric techniques, for topographic mapping in these areas, is expensive or even not possible due to adverse atmospheric conditions. With the launch of the Canadian RADARSAT-1 in 1995, altimetric information extracted from DSM could be for the first time systematically generated using orbital SAR (Synthetic Aperture Radar) radargrammetry or stereoscopy (Toutin 1999). With the ASTER sensor, launched in 1999 on board of Terra platform, it was possible to generate spaceborne optical stereoscopic DSMs from the nadir and backwards positions of the VNIR band 3 (Hirano et al 2003)

Methods

Results

Conclusion