NAME
r.viewshed.cva - Undertakes a "cumulative viewshed analysis" using a vector points map as input "viewing" locations, using r.viewshed to calculate the individual viewsheds.
KEYWORDS
raster,
viewshed,
line of sight,
LOS
SYNOPSIS
r.viewshed.cva
r.viewshed.cva --help
r.viewshed.cva [-kcrbe] input=name vector=name output=name [observer_elevation=float] [target_elevation=float] [max_distance=float] [memory=integer] [refraction_coeff=float] [name_column=name] [--overwrite] [--help] [--verbose] [--quiet] [--ui]
Flags:
- -k
- Keep all interim viewshed maps produced by the routine (maps will be named "vshed_'name'_uniquenumber", where 'name' is the value in "name_column" for each input point. If no value specified in "name_column", cat value will be used instead)
- -c
- Consider the curvature of the earth (current ellipsoid)
- -r
- Consider the effect of atmospheric refraction
- -b
- Output format is {0 (invisible) 1 (visible)}
- -e
- Output format is invisible = NULL, else current elev - viewpoint_elev
- --overwrite
- Allow output files to overwrite existing files
- --help
- Print usage summary
- --verbose
- Verbose module output
- --quiet
- Quiet module output
- --ui
- Force launching GUI dialog
Parameters:
- input=name [required]
- Input elevation map (DEM)
- vector=name [required]
- Name of input vector map
- Name of input vector points map containg the set of points for this analysis.
- output=name [required]
- Output cumulative viewshed raster
- observer_elevation=float
- Height of observation points off the ground
- Default: 1.75
- target_elevation=float
- Height of target areas off the ground
- Default: 1.75
- max_distance=float
- Maximum visibility radius. By default infinity (-1)
- Default: -1
- memory=integer
- Amount of memory to use (in MB)
- Default: 500
- refraction_coeff=float
- Refraction coefficient (with flag -r)
- Options: 0.0-1.0
- Default: 0.14286
- name_column=name
- Database column for point names (with flag -k)
r.viewshed.cva is a module that allows for the
construction of "Cumulative Viewshed", or "visualscape" maps from a
series of input points stored in a vector points map. The routine is
a python wrapper script that iterative loops through each input
point, calculating a viewshed map, and then creates an output map
that is coded by the number of input locations that can "see" each
cell.
r.viewshed.cva uses the GRASS GIS module
r.viewshed
for the viewshed analysis.
r.viewshed is very fast,
thus allowing for a cumulative viewshed analysis to run in a
reasonable amount of time. The final cumulative viewshed map is
computed using the "count" method of
r.series, rather than
with mapcalc, as it better handles the null values in the individual
constituent viewshed maps (and allows for interim viewshed maps to
be coded in any way).
r.viewshed.cva requires an input elevation map,
input,
and an input vector points map,
vector. There is currently only
one native flag for
r.viewshed.cva,
-k, which allows
you to keep the interim viewshed maps made for each input point.
Optionally, option
name_column can be used with
-k to specify
the suffix of the kept viewshed maps by a particular column in the
input vector points' database. If no value is specified for
name_column,
then the cat value will be used.
All other flags and options are inherited from
r.viewshed
(see the r.viewshed
help page for more information on these).
The input vector points map can be manually digitized (with
v.digit) over topographic or cultural features, or can be
created as a series of random points (with
r.random or
v.random). Note that using the flag -k allows you to keep any
interim viewshed maps created during the analysis, and these resultant
viewshed maps will be named according to the cat number of the original
input points. This is also useful for simple creating a large number
of individual viewsheds from points in a vector file.
An automated summit extraction can be done with r.geomorphon.
Undertake a cumulative viewshed analysis from a digitized vector points
map of prominent peaks in a region (North Carolina sample dataset):
g.region raster=elevation -p
# use v.digit to digitize points or e.g. the r.geomorphon addon for summits
r.viewshed.cva input=elevation output=peaks_CVA_map \
vector=prominent_peaks_points name_column=cat \
observer_elevation=1.75 target_elevation=0
Undertake a cumulative viewshed analysis from a 10% sample of
landscape locations in a region:
g.region raster=elevation -p
r.random input=elevation n=10% vector=rand_points_10p
r.viewshed.cva input=elevation output=peaks_CVA_map \
vector=rand_points_10p name_column=cat \
observer_elevation=1.75 target_elevation=0
r.geomorphon,
r.viewshed
Isaac Ullah
SOURCE CODE
Available at:
r.viewshed.cva source code
(history)
Latest change: Monday Jan 30 19:52:26 2023 in commit: cac8d9d848299297977d1315b7e90cc3f7698730
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GRASS Development Team,
GRASS GIS 8.4.1dev Reference Manual