gdal_viewshed - Calculates a viewshed raster from an input raster
DEM for a user defined point
gdal_viewshed [-b <band>]
[-a_nodata <value>] [-f <formatname>]
[-oz <observer_height>] [-tz <target_height>] [-md <max_distance>]
-ox <observer_x> -oy <observer_y>
[-vv <visibility>] [-iv <invisibility>]
[-ov <out_of_range>] [-cc <curvature_coef>]
[[-co NAME=VALUE] ...]
[-q] [-om <output mode>]
<src_filename> <dst_filename>
By default the gdal_viewshed generates a binary visibility
raster from one band of the input raster elevation model (DEM). The output
raster will be of type Byte. With the -mode flag can also return a minimum
visible height raster of type Float64.
NOTE:
The algorithm as implemented currently will only output
meaningful results if the georeferencing is in a projected coordinate
reference system.
- -co
<NAME=VALUE>
- Many formats have one or more optional creation options that can be used
to control particulars about the file created. For instance, the GeoTIFF
driver supports creation options to control compression, and whether the
file should be tiled.
The creation options available vary by format driver, and some
simple formats have no creation options at all. A list of options
supported for a format can be listed with the --formats command line
option but the documentation for the format is the definitive source of
information on driver creation options. See raster_drivers format
specific documentation for legal creation options for each format.
- -b <band>
- Select an input band band containing the DEM data. Bands are
numbered from 1. Only a single band can be used. Only the part of the
raster within the specified maximum distance around the observer point is
processed.
- -a_nodata
<value>
- The value to be set for the cells in the output raster that have no data.
NOTE:
Currently, no special processing of input cells at a
nodata value is done (which may result in erroneous results).
- -ox <value>
- The X position of the observer (in SRS units).
- -oy <value>
- The Y position of the observer (in SRS units).
- -oz <value>
- The height of the observer above the DEM surface in the height unit of the
DEM. Default: 2
- -tz <value>
- The height of the target above the DEM surface in the height unit of the
DEM. Default: 0
- -md <value>
- Maximum distance from observer to compute visibiliy. It is also used to
clamp the extent of the output raster.
- -cc <value>
- Coefficient to consider the effect of the curvature and refraction. The
height of the DEM is corrected according to the following formula:
Height_{Corrected}=Height_{DEM}-{CurvCoeff}\frac{{TargetDistance}^2}{SphereDiameter}
For atmospheric refraction we can use 0.85714
- -iv <value>
- Pixel value to set for invisible areas. Default: 0
- -ov <value>
- Pixel value to set for the cells that fall outside of the range specified
by the observer location and the maximum distance. Default: 0
- -vv <value>
- Pixel value to set for visible areas. Default: 255
- -om <output
mode>
- Sets what information the output contains.
Possible values: VISIBLE, DEM, GROUND
VISIBLE returns a raster of type Byte containing visible
locations.
DEM and GROUND will return a raster of type Float64 containing
the minimum target height for target to be visible from the DEM surface
or ground level respectively. Flags -tz, -iv and -vv will be
ignored.
Default VISIBLE
Functionality of this utility can be done from C with
GDALViewshedGenerate().
Compute the visibility of an elevation raster data source with
defaults
[image] A computed visibility for two separate -ox
and -oy points on a DEM..UNINDENT
gdal_viewshed -md 500 -ox -10147017 -oy 5108065 source.tif destination.tif
- [Wang2000]
- Generating Viewsheds without Using Sightlines. Wang, Jianjun, Robinson,
Gary J., and White, Kevin. Photogrammetric Engineering and Remote Sensing.
p81.
https://www.asprs.org/wp-content/uploads/pers/2000journal/january/2000_jan_87-90.pdf
Tamas Szekeres <szekerest@gmail.com>