GIS for Cave Surveyors Part 2 - Terrain Detail

So far we have produced a map showing the cave locations but this is useless unless we can relate it to the real world.

We can achieve this by adding a coordinate grid. We do this at the output stage which I'll get to later.

In the meantime we can add contours but first we need to get some terrain data. These data are DEM's or Digital Elevation Models which are available from various sources. I get mine here.

Download the area in which you are interested and import into QGIS from the Layer - Add Raster Layer menu selection. Point the file browser to the DEM you download, a filename something like this ASTGTM_N53W002_dem.tif.

You should now have something like this

 This layer consists of a tiff file with each pixel having an altitude attribute. We can extract these altitude data and create contours from them. Click on Raster - extraction - contour and a dialogue window will open

Enter an output filename , select a contour interval and click OK.

Turn off the DEM layer and you should now have something like this