Absolute and relative height-pixel accuracy of SRTM-GL1 over the South American Andean Plateau

Frédéric Satge, Matheus Denezine, Ramiro Pillco, Franck Timouk, Sébastien Pinel, Jorge Molina, Jérémie Garnier, Frédérique Seyler, Marie Paule Bonnet

Research output: Contribution to journalArticlepeer-review

29 Scopus citations


Previously available only over the Continental United States (CONUS), the 1 arc-second mesh size (spatial resolution) SRTM-GL1 (Shuttle Radar Topographic Mission – Global 1) product has been freely available worldwide since November 2014. With a relatively small mesh size, this digital elevation model (DEM) provides valuable topographic information over remote regions. SRTM-GL1 is assessed for the first time over the South American Andean Plateau in terms of both the absolute and relative vertical point-to-point accuracies at the regional scale and for different slope classes. For comparison, SRTM-v4 and GDEM-v2 Global DEM version 2 (GDEM-v2) generated by ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) are also considered. A total of approximately 160,000 ICESat/GLAS (Ice, Cloud and Land Elevation Satellite/Geoscience Laser Altimeter System) data are used as ground reference measurements. Relative error is often neglected in DEM assessments due to the lack of reference data. A new methodology is proposed to assess the relative accuracies of SRTM-GL1, SRTM-v4 and GDEM-v2 based on a comparison with ICESat/GLAS measurements. Slope values derived from DEMs and ICESat/GLAS measurements from approximately 265,000 ICESat/GLAS point pairs are compared using quantitative and categorical statistical analysis introducing a new index: the False Slope Ratio (FSR). Additionally, a reference hydrological network is derived from Google Earth and compared with river networks derived from the DEMs to assess each DEM's potential for hydrological applications over the region. In terms of the absolute vertical accuracy on a global scale, GDEM-v2 is the most accurate DEM, while SRTM-GL1 is more accurate than SRTM-v4. However, a simple bias correction makes SRTM-GL1 the most accurate DEM over the region in terms of vertical accuracy. The relative accuracy results generally did not corroborate the absolute vertical accuracy. GDEM-v2 presents the lowest statistical results based on the relative accuracy, while SRTM-GL1 is the most accurate. Vertical accuracy and relative accuracy are two independent components that must be jointly considered when assessing a DEM's potential. DEM accuracies increased with slope. In terms of hydrological potential, SRTM products are more accurate than GDEM-v2. However, the DEMs exhibit river extraction limitations over the region due to the low regional slope gradient.

Original languageEnglish
Pages (from-to)157-166
Number of pages10
JournalISPRS Journal of Photogrammetry and Remote Sensing
StatePublished - 1 Nov 2016

Bibliographical note

Funding Information:
This work was supported by the Centre National d’Etudes Spatiales (CNES) in the framework of the HASM project (Hydrology of Altiplano: from Spatial to Modeling). The first author thanks the IRD ( Institut de Recherche pour le Développement ) and CAPES ( Coordenação de Aperfeiçoamento de Pessoal de Nível Superior ) Brazil for their financial support. The authors are also thankful for the two anonymous reviewers for their constructive reviews that enhanced this work.

Publisher Copyright:
© 2016 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS)


  • Accuracy
  • Andean Plateau
  • Digital elevation model
  • SRTM
  • South America


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