v.rast.bufferstats - GRASS GIS manual

NAME

v.rast.bufferstats - Calculates statistics of raster map(s) for buffers around vector geometries.

KEYWORDS

SYNOPSIS

v.rast.bufferstats

v.rast.bufferstats --help

v.rast.bufferstats [-tpur] input=name raster=name[,name,...] buffers=integer[,integer,...] type=string[,string,...] [layer=string] column_prefix=string[,string,...] [methods=string[,string,...]] [percentile=integer] [output=name] [separator=character] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:

-t: Tabulate area within buffers for categories in raster map(s)
-p: Used with -t flag will return percentage of area for categories
-u: Update columns if they already exist
-r: Remove columns without data
--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]: Name of input vector map; Vector map containing geometries to compute buffer statistics for
raster=name[,name,...] [required]: Raster map(s) to calculate statistics from
buffers=integer[,integer,...] [required]: Buffer distance(s) in map units
type=string[,string,...] [required]: Vector type to work on; Options: points, lines, areas; Default: points,lines,areas
layer=string: Layer number or name; Vector features can have category values in different layers. This number determines which layer to use. When used with direct OGR access this is the layer name.; Default: 1
column_prefix=string[,string,...] [required]: Column prefix for new attribute columns
methods=string[,string,...]: The methods to use; Options: number, number_null, minimum, maximum, range, sum, average, average_abs, stddev, variance, coeff_var, first_quartile, median, third_quartile; Default: number,number_null,minimum,maximum,range,sum,average,average_abs,stddev,variance,coeff_var,first_quartile,median,third_quartile
percentile=integer: Percentile to calculate; Options: 0-100
output=name: Name for output file (if "-" output to stdout)
separator=character: Field separator; Field separator in output file; Default: |

DESCRIPTION:
NOTE
EXAMPLES
KNOWN ISSUES
SEE ALSO
AUTHOR

DESCRIPTION:

The purpose of the v.rast.bufferstats module is to provide local environmental context to a series of input geometries. It computes statistics from multiple input raster maps within multiple buffers around selected geometries in the input vector map.

Available statistics are either

statistics provided by r.univar or
if the t-flag is checked - area of, number of and/or the most frequent (mode) raster categories within the buffers using r.stats.

If output option is specified, results are written to file or stdout in stead of attribute table of the input map. File output is produced with the following column order:
cat | prefix | buffer| statistic/measure | value
separated by the user defined separator (default is |).

NOTE

The module temporarily modifies the computational region. The region is set to the extent of the respecive buffers, while the alignement of the current region is kept.

EXAMPLES


g.region -p raster=elevation,geology_30m
v.clip --o -r input=bridges output=bridges_wake

# Tabulate area of land cover map
g.region -p raster=elevation,geology_30m align=geology_30m
v.rast.bufferstats -t input=bridges_wake raster=geology_30m buffers=100,250,500 column_prefix=geology

# Compute terrain statistics
g.region -p raster=elevation,geology_30m align=elevation
r.slope.aspect elevation=elevation slope=slope aspect=aspect
v.rast.bufferstats input= raster=altitude,slope,aspect buffers=100,250,500 column_prefix=altitude,slope,aspect methods=minimum,maximum,average,stddev percentile=5,95

KNOWN ISSUES

In order to avoid topological issues with overlapping buffers, the module loops over the input geometries. However, this comes at costs with regards to performance. For a larger number of geometries in the vector map, it can be therefore more appropriate to compute neighborhood statistics with r.neighbors and to extract (v.what.rast, r.what) or aggregate (v.rast.stats) from those maps with neighborhood statistics.

The module is affected by the following underlying library issues: Lines are wrongly reported for points maps: https://trac.osgeo.org/grass/ticket/3549 To circumvent the issue, specify the type of geometry to process in the module call using the type option. Currently, the module uses GRASS native buffering which should be replaced by buffering using GEOS: https://trac.osgeo.org/grass/ticket/3628

AUTHOR

Stefan Blumentrath, Norwegian Institute for Nature Research, Oslo, Norway

SOURCE CODE

Available at: v.rast.bufferstats source code (history)