## NAME

r.los - Line-of-sight raster analysis program.
(GRASS Raster Program)

## SYNOPSIS

r.los
r.los help
r.los input=name output=name coordinate=x,y [patt_map=name] [obs_elev=value] [max_dist=value]

## DESCRIPTION

r.los generates a raster map output in which the cells that are visible from a user-specified observer location are marked with integer values that represent the vertical angle (in degrees) required to see those cells (viewshed).

The program can be run either non-interactively or interactively. To run r.los non-interactively, the user must specify at least an input file name, output file name, and the geographic coordinates of the user's viewing location on the command line; any remaining parameters whose values are unspecified on the command line will be set to their default values (see below). Non-interactive usage format is:

  r.los input=name output=name coordinate=x,y [patt_map=name] [obs_elev=value] [max_dist=value]

Alternately, the user can type simply r.los on the command line; in this case, the program will prompt the user for parameter values using the standard GRASS parser.

### Parameters:

input=name
  Name of a raster map layer containing elevation data, used as program input.
output=name
  Name assigned to the file in which the raster program output will be stored.
coordinate=x,y
  Geographic coordinates (i.e., easting and northing values) identifying the desired location of the viewing point.
patt_map=name
  Name of a binary (1/0) raster map layer in which cells within the areas of interest are assigned the category value '1', and all other cells are assigned the category value '0'. If this parameter is omitted, the analysis will be performed for the whole area within a certain distance of the viewing point inside the geographic region boundaries.
  Default: assign all cells that are within the max_dist and within the user's current geographic region boundaries a value of 1.
obs_elev=value
  Height of the observer (in meters) above the viewing point's elevation.
  Default: 1.75 (meters)
max_dist=value
  Maximum distance (in meters) from the viewing point inside of which the line of sight analysis will be performed. The cells outside this distance range are assigned the category value '0'.
  Options: 0-99999 (stated in map units)
  Default: 1000

## NOTES

For accurate results, the program must be run with the resolution of the geographic region set equal to the resolution of the data (see g.region).

It is advisable to use a 'pattern layer' which identifies the areas of interest in which the line of sight analysis is required. Such a measure will reduce the time taken by the program to run.

## SEE ALSO

g.region
parser

## AUTHOR

Kewan Q. Khawaja, Intelligent Engineering Systems Laboratory, M.I.T.

Last changed: $Date: 2002/01/25 05:45:34 $