Original Research

The first sub-meter resolution digital elevation model of the Kruger National Park, South Africa

Kai Heckel, Marcel Urban, Jean-Sébastien Bouffard, Jussi Baade, Peter Boucher, Andrew Davies, Evan G. Hockridge, Wolfgang Lück, Jonas Ziemer, Izak Smit, Bernhard Jacobs, Mark Norris-Rogers, Christiane Schmullius
Koedoe | Vol 63, No 1 | a1679 | DOI: https://doi.org/10.4102/koedoe.v63i1.1679 | © 2021 Kai Heckel, Marcel Urban, Jean-Sébastien Bouffard, Jussi Baade, Peter Boucher, Andrew Davies, Evan G. Hockridge, Wolfgang Lück, Jonas Ziemer, Izak Smit, Bernhard Jacobs, Mark Norris-Rogers, Christiane Schmullius | This work is licensed under CC Attribution 4.0
Submitted: 02 March 2021 | Published: 17 December 2021

About the author(s)

Kai Heckel, Department for Earth Observation, Faculty of Chemistry and Earth Sciences, Friedrich Schiller University, Jena, Germany; and, Earth Observation Services (EOS), Jena, Germany
Marcel Urban, Department for Earth Observation, Faculty of Chemistry and Earth Sciences, Friedrich Schiller University, Jena, Germany
Jean-Sébastien Bouffard, CATALYST, Ottawa, Canada
Jussi Baade, Department for Physical Geography, Faculty of Chemistry and Earth Sciences, Friedrich Schiller University, Jena, Germany
Peter Boucher, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States of America
Andrew Davies, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States of America
Evan G. Hockridge, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States of America
Wolfgang Lück, Pinkmatter North America, Victoria, Canada
Jonas Ziemer, Department for Earth Observation, Faculty of Chemistry and Earth Sciences, Friedrich Schiller University, Jena, Germany
Izak Smit, Scientific Services, South African National Parks (SANParks), Skukuza, South Africa; and, Centre for African Ecology, School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa
Bernhard Jacobs, Geospace International, Pretoria, South Africa
Mark Norris-Rogers, RasterMatics International, uMgungundlova, South Africa
Christiane Schmullius, Department for Earth Observation, Faculty of Chemistry and Earth Sciences, Friedrich Schiller University, Jena, Germany


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Abstract

The use of digital elevation models has proven to be crucial in numerous studies related to savanna ecosystem research. However, the insufficient spatial resolution of the chosen input data is often considered to be a limiting factor when conducting local to regional scale ecosystem analysis. The elevation models and orthorectified imagery created in this study represent the first wall-to-wall digital elevation data sets produced for the Kruger National Park (KNP), South Africa, at very high spatial resolution. Using colour-infrared (CIR) aerial imagery from the archives of the Chief Directorate: National Geo-spatial Information (CDNGI), Department of Agriculture, Land Reform and Rural Development (DALRRD) aerial acquisition programme, we created digital surface models (DSMs), digital terrain models (DTMs) and CIR orthomosaics covering the entire KNP with a nominal ground sampling distance of 0.25 m. Elevation information was derived using state-of-the-art stereo matching algorithms that utilised semi-global matching (SGM) as a cost aggregation function throughout the image pairing, using the Enterprise software from CATALYST. The final products were validated against reference products, and showed excellent agreement with R² values of 0.99. Further, the validation of the DTM and DSM revealed median absolute vertical height error (LE90) across all sites of 1.02 m and 2.58 m, respectively. The orthomosaics were validated with in situ ground control points (GCPs) exhibiting a horizontal Circular Probable Error (CPE) of 1.37 m. The data resulting from this work will be distributed freely with the aim of fostering more scientific studies in the African science community and beyond.

Conservation implications: Accurate information about terrain and surface height are crucial inputs to a variety of scientific analysis, which are essential in protected areas, such as flood prediction or fire hazard estimation. Elevation data sets and orthomosaics in very high resolution can therefore serve as a crucial tool to improve park management and foster positive implications on conservation efforts.


Keywords

Kruger National Park; elevation; aerial imagery; semi-global matching; stereoscopy; 3D; protected areas

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