Raster Meets Point Data - Open Source Geospatial Tools: Applications in Earth Observation - page 152

(a) (b)

0 25 50 km 0 25 50 km

(c) Contour (m)

5000
10000
15000
20000
25000

0 25 50 km

Fig. 10.4 Using gdal_proximity.py to create a warning contour around active fire regions.
a Raster map with active fires. b Distance map using -maxdist of 25km. c Contour vector with
intervals of 5km

gdal_contour -a distance -i 5000 distance.tif warning.shp

10.6 gdaldem

The gdaldem command line utility can be used to analyze and visualize a digital
elevation model (DEM) in raster format. Point datasets in a LiDAR format such
as LAS need to be converted to raster format first (see Chap. 15 ) . The gdaldem
utility has seven different modes that produces different types of output: hillshade,
slope, aspect, color-relief, terrain ruggedness index (TRI), topographic position index
(TPI) and roughness. All modes, except for the color-relief mode, use a 3 3moving

window for calculating the output. If the the window contains a no-data value in the
input DEM, the algorithm will produce a no-data value in the output. To interpolate
no-data values, you can set the option -compute_edges . Mode specific options
are further described in the respective sections.

×

Usage: gdaldem
ₒ

[hillshade|slope|aspect|color-relief|TRI|TPI| roughness]

ₒ

input_dem output_xxx_map [-of format] [-compute_edges]

ₒ

[-alg ZevenbergenThorne] [b band] [-co name=value]* [-q]