[GRASS-user] Euclidean distance (grow.distance) on raster to certain extent?

[Moritz Lennert]

On 07/05/12 16:36, Daniel Lee wrote:
> Hi Tanya,
>
> I would use r.distance rather than r.grow.distance and then reclassify
> the results to include only areas with <=1108 m distance - that should
> be a lot easier.

I don't think r.distance gives what you want, however r.grow.distance 
should be exactly your tool:

As a starting point you need a raster map with all pixels in the orchard 
non-null and all other pixels null  Let's call that raster map 
'orchard'. Then you can do the following:

r.grow.distance input=orchard distance=distance_map

Then, if you only want to see the distance from the orchard to 1108m, 
then you can use r.mapcalc:

r.mapcalc "final_distance_map=if(distance_map>1108, null(), distance_map)"

All this keeping in mind that I don't understand what you mean by "I 
recognize this tool does not allow a distance to be included".

If this means that you also want to measure a distance _within_ the 
orchard, then instead of using a raster map of the orchard, use as input 
to r.grow.distance a raster map with only the center pixel of the 
orchard non-null.

Moritz

>
> 2012/5/7 Tanya Dyck <tanya.dyck at hotmail.com <mailto:tanya.dyck at hotmail.com>>
>
>     Hello,
>
>     I am trying to run the grow.distance command to create a raster that
>     displays the euclidean distance from an 'orchard' outward to 1108m.
>       I am not trying to measure the distance between 2 non-null
>     features, but simply wish to have the euclidean distance extend out
>     from the orchard to 1108m.  I recognize this tool does not allow a
>     distance to be included so I created a buffer around my orchard
>     (1108m) and intended to run grow.distance on that, however it
>     outputs the distance as if it includes the full raster extent (so I
>     have an output raster of 1108m that is all yellow as opposed to a
>     range of values displaying varying distances) and not limited to my
>     buffer. I want it to assume the buffer extent is the raster extent,
>     so to speak.  Is there another way to do this?
>     Any ideas would be much appreciated.
>
>     Best,
>
>     Tanya
>
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