[R-sig-Geo] shortest realistic distance for fish travel

[Dylan Beaudette]

On Thursday 18 December 2008, Jon Loehrke wrote:
> Hi,
>
> 	I am trying to find an algorithm or thoughts on approach for how to
> compute the shortest realistic distance between two points.  I define
> shortest realistic distance as the shortest distance between two
> points that a fish (which is what I study) could move through.  Hence
> the path must wrap around land, islands, archipelagos, etc.
>
> Point 1
>
> 41.15  	N
> 71.26 	W
>
> Point 2
>
> 42.17  	N
> 70.37 	W
>
> 	I'm sure this issue has come up with the geo-statistical community,
> but simply need a starting direction.
>
> Thank much and happy holidays.

Hi,

This isn't a geo-statistics approach, but simple cost-surface algorithms 
should be able to do this without too much work.

An example in GRASS:

http://casoilresource.lawr.ucdavis.edu/drupal/node/544

You could make the non-water regions a 'really high' static cost, such that 
finding the least-cost path would be constrained to water.

Cheers,

Dylan




> Jon Loehrke
> Graduate Research Assistant
> Department of Fisheries Oceanography
> School for Marine Science and Technology
> University of Massachusetts
> 200 Mill Road, Suite 325
> Fairhaven, MA 02719
> jloehrke at umassd.edu
> T 508-910-6393
> F 508-910-6396
>
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-- 
Dylan Beaudette
Soil Resource Laboratory
http://casoilresource.lawr.ucdavis.edu/
University of California at Davis
530.754.7341