[GRASS-user] Distance layer

Nomad Rain nomadrain at gmail.com
Sun Oct 29 13:08:24 EST 2006

Jachym, thank you for reply, I am going the same way.

The  solution  for  the  problem  has  been already published by David
Finlayson  in his r.eucdist - I found it on GRAS wiki ((C) 2006 by the
GRASS  Development  Team).  I  think  it is desirable to include it in
GRASS  distribution  for  a lot of applications need to find result of
function  from  distance  of  certain  points  and r.eucdist is a fine
example how2do it without programming.

r.eucdist  is a script wich uses replacement of null values and then -
r.cost  +  r.mapcalc's  nsres()  to  find  the Euclidean distance from
points  to every pixel. The COSTS input map for r.cost is set equal to
nsres(),   as   a   value   for  every  pixel.  However,  as  I  know,
(nsres()+ewres())/2) is more correct, maybe becouse I have not met the
maps with very different NS and EW resolutions.

IMHO man page for r.cost doesn't clearly define procedures like this.

I am still working on my script and going to publish it under GPL

Victor Yeliseyev

> hi,

> would it be problem to separate NULL values from your map? e.g.
> r.mapcalc yourmap2=if(isnull(yourmap),1,null())
> than you can use r.distance

> jachym

> On Sat, Oct 28, 2006 at 07:11:04PM +0300, Nomad Rain wrote:
>> Thank you, Dylan and Jachym
>> I tried r.distance (the problem mentioned doesn't prevent)
>> Yes  it  gives  me  distances between raster pixels. However I need to
>> calculate in cycle all the distances from the only point to every NULL
>> pixel in region on new layer.
>> And r.distance does not work with null values, do it?
>> Help please, because my intuition keeps silence
>> ---

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