NAME

       r.spreadpath   -  Recursively traces the least cost path backwards to cells from which the
       cumulative cost was determined.

KEYWORDS

       raster, fire

SYNOPSIS

       r.spreadpath
       r.spreadpath help
       r.spreadpath [-v] x_input=string y_input=string  [coordinate=x,y[,x,y,...]]  output=string
       [--overwrite]  [--verbose]  [--quiet]

   Flags:
       -v
           Run verbosely

       --overwrite
           Allow output files to overwrite existing files

       --verbose
           Verbose module output

       --quiet
           Quiet module output

   Parameters:
       x_input=string
           Name of raster map containing back-path easting information

       y_input=string
           Name of raster map containing back-path northing information

       coordinate=x,y[,x,y,...]
           The map E and N grid coordinates of starting points

       output=string
           Name of spread path raster map

DESCRIPTION

       r.spreadpath  recursively  traces  the  least  cost  path  backwards  to the origin, given
       backlink information input map layers and target locations from  where  paths  are  to  be
       traced.  The backlink information map layers record each cell's backlink UTM northing (the
       y_input) and easting (the x_input) coordinates from which the cell's cumulative  cost  was
       determined.

       The  backlink  inputs  can be generated from another GRASS raster program r.spread. One of
       the major applications of r.spreadpath along with r.spread is to accurately find the least
       cost  corridors  and/or  paths  on  a  raster  setting.  More  information on r.spread and
       r.spreadpath can be found in Xu (1994).

Parameters:

       x_input=name
              Name of input raster map layer containing backlink UTM easting coordinates.

       y_input=name
              Name of input raster map layer containing backlink UTM northing coordinates.

       coordinate=x,y[,x,y,x,y, ...]
              Each x,y coordinate pair gives the easting and northing  (respectively)  geographic
              coordinates of a target point from which to backwards trace the least cost path. As
              many points as desired can be entered by the user.

       output=name
              Name of raster map layer to contain output. Also can be used as the  map  layer  of
              the input target points. If so used, the input target point map will be overwritten
              by the output.

SEE ALSO

       r.spread, r.ros

REFERENCES

       Xu, Jianping, 1994, Simulating the spread of  wildfires  using  a  geographic  information
       system  and  remote  sensing,  Ph. D. Dissertation, Rutgers University, New Brunswick, New
       Jersey.

AUTHOR

       Jianping Xu and Richard G. Lathrop, Jr., Center for Remote Sensing and  Spatial  Analysis,
       Rutgers University.

       Last changed: $Date: 2003-05-06 09:41:37 -0700 (Tue, 06 May 2003) $

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