[GRASSLIST:4841] Re: best way to grow a distance layer?

[Markus Neteler]

On Fri, Oct 25, 2002 at 06:28:29PM -0400, William W. Hargrove wrote:
> I want to grow distance rings around some features in a large, high resolution
> map.
> 
> Looks like r.buffer will do the job, but it only takes up to 60 buffer rings,
> and this won't get me to the edge of the large map with a resolution of one
> cell width.
> 
> Is there a single command in GRASS that will grow a distance layer out to the
> edge of the map?

Not a single command, but a combination of two commands:
You can use r.cost with input map containing 1 as values. Then, to
translate the distance to meters, multiply with cell resolution.

Eg. something like distances to roads:

g.region rast=roads
r.mapcalc area.one=1
r.cost input=area.one output=distance start_rast=roads
r.mapcalc dist_meters="distance * ewres()"

Hope this helps somehow,

 Markus

-- 
Markus Neteler

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