Mapping Hacks

Add Relief to Your Topographic Maps #72

Chapter 6, Mapping on Your Desktop

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347

HACK

Now you can zoom in and out as you like and return to this view of San

Francisco by typing

g.region San_Francisco, followed by d.redraw.

If you got a single DEM from the USGS Seamless Data Dis-

tribution System or the Global Land Cover Facility, you can

skip over this next part.

Making a Composite Elevation Model

Next, let’s get the DEMs we downloaded imported into GRASS as raster lay-

ers. Ordinarily, r.in.gdal can be used to read DEM files directly into GRASS,

but, for reasons unclear, this causes segmentation faults in the version of

GRASS we used. However, the GDAL package offers a tool called gdal_

translate, which will let us turn the DEMs into GeoTIFFs, and then r.in.gdal

can import those GeoTIFFs into GRASS as usual. Because there are a few

DEM files we want to convert, we wrote a quick bash script called import_

dem.sh to do the job:

#!/bin/bash

for dem in $@; do

Figure 6-34. The USGS DRG for San Francisco, imported into GRASS