Digital Elevation Model (DEM) Processing

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This section is still under construction! This article was last modified on 01/21/2014. If you have comments please use the Discussion page or contribute to the article!

This article is part of the QGIS tutorial 2013/14.
In this article you will learn how to pre-process and enhance digital elevation model (DEM) data, as well as how to create a 3D-Model

Loading, merging and reprojection of DEM data

1. Add the raster layers N51E009.hgt and N51E010.hgt to a new QGIS project (from geodata\raster\DEM, see Course data). Arrange the first above the latter layer.
2. Merging layers
   • Select Raster --> Miscellaneous --> Merge. In the appearing menu, click the Select beside the Input files field. Browse for the maps N51E009.hgt and N51E010.hgt and select both (by clicking with pressed Ctrl key) (figure A).
   • Select an output directory and file name (e.g. N510_merged) under Output file. Confirm with OK.
3. Reprojecting layers (warp)
   • Select Raster --> Projections --> Warp (reprojects).
   • As Input file choose the merged layer from the preceding step. Select an according path and file name for Output file.
   • Determine the correct source and target spatial reference system (Source SRS and Target SRS) -- The coordinate system of the source layer is WGS84 (EPSG:4326). Use UTM32 (EPSG:32632) as target (figure B).
   • Confirm with OK.

Figure A: Merge dialogue and file browser in QGIS 2.0

Figure B: Warp dialogue and menu for SRS selection in QGIS 2.0

Clipping and Resampling of DEM data

1. Create a boundary polygon
   1. Add the raster map geodata/raster/landsat/landsat8/DOY156/SUB_LC81950242013156LGN00_B1 from the course data to the project.
   2. Select Vector --> Research tools --> Polygon from layer extent. Choose the landsat map as input, select an output path and file name and confirm with OK.