Scripting methods in topographic data processing on the example of Ethiopia

Polina Lemenkova

doi:10.4314/sinet.v44i1.9

Abstract

This study evaluates the geomorphometric parameters of the topography in Ethiopia using scripting cartographic methods by applying R languages (packages 'tmap' and 'raster') and Generic Mapping Tools (gmt) for 2D and 3D topographic modelling. Data were collected from the open source repositories on geospatial data with high resolution: gebco with 15 arc-second and etopo1 with 1 arc-minute resolution and embedded dataset of srtm 90 m in 'raster' library of R. The study demonstrated application of the programming approaches in cartographic data visualization and mapping for geomorphometric analysis. This included modelling of slope steepness, aspect and hillshade visualized using dem srtm90 to derive geomorphometric parameters of slope, aspect and hillshade of Ethiopia and demonstrate contrasting topography and variability climate setting of Ethiopia. The topography of the country is mapped, including Great Rift Valley, Afar Depression, Ogaden Desert and the most distinctive features of the Ethiopian Highlands. A variety of topographical zones is demonstrated on the presented maps. The results include 6 new maps made using programming console-based approach which is a novel method of cartographic visualization compared to traditional gis software. The most important fragments of the codes are presented and technical explanations are provided. The presented series of 6 new maps contributes to the cartographic data on Ethiopia and presents the methodology of scripting mapping techniques.

Highlights

Geomorphometry ContextThis study presents the geomorphometric modelling and 2D and 3D topographic mapping of Ethiopia by scripting technologies of Generic Mapping Tools (GMT) and R
The results present a series of the six maps of the topography of Ethiopia demonstrating cartographic modelling using 2D and 3D perspective views
Analysis of topographic data based on the GEBCO/SRTM in Ethiopia (Fig. 1) confirmed the general decline in the elevation in the Afar Depression and the Great Rift Valley which shows the distribution of the major tectonic fault lines controlling the topographic curvature demonstrated in topographic 2D map (Fig. 1) and 3D model (Fig. 2)

Summary

Introduction

Geomorphometry ContextThis study presents the geomorphometric modelling and 2D and 3D topographic mapping of Ethiopia by scripting technologies of GMT and R. Geomorphometry has been an object of recent activity in publications on the terrain mapping, applications of the advanced methods of quantitative DEM modelling, high-resolution spatial data processing and land-surface analysis (Bishop et al, 2003; Gessler et al, 2009; Guth, 2009; Wang et al, 2010; Drăguţ et al, 2011; Alvioli et al, 2016). The DEM can be mapped effectively to derive the geomorphometric parameters (slope and aspect of the local topography) and to calculate hill shade visualizations with perspective view, especially for DEM and raster data with high resolution (Chang and Tsai 1991; Deng et al, 2007; Lemenkova, 2020f, 2020g)

Methods

Results

Discussion

Conclusion