shortest realistic distance for fish travel

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shortest realistic distance for fish travel

Jon Loehrke
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.

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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shortest realistic distance for fish travel

Sarah Goslee
Hi,

That sounds like a least-cost path problem.

Sarah

On Thu, Dec 18, 2008 at 2:38 PM, Jon Loehrke <jloehrke at umassd.edu> 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.
>


--
Sarah Goslee
http://www.functionaldiversity.org



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shortest realistic distance for fish travel

Dylan Beaudette
In reply to this post by Jon Loehrke
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
>
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo at stat.math.ethz.ch
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo



--
Dylan Beaudette
Soil Resource Laboratory
http://casoilresource.lawr.ucdavis.edu/
University of California at Davis
530.754.7341



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shortest realistic distance for fish travel

Alisa Coffin-2
In reply to this post by Jon Loehrke
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shortest realistic distance for fish travel

van Etten, Jacob (IRRI)
You could also look at "resistance distance" (open-source software available at http://www.circuitscape.org/) if your fish travel as random-walkers.

Jacob van Etten

-----Original Message-----
From: r-sig-geo-bounces at stat.math.ethz.ch on behalf of Alisa Coffin
Sent: Fri 19/12/2008 04:16
To: Jon Loehrke
Cc: r-sig-geo at stat.math.ethz.ch
Subject: Re: [R-sig-Geo] shortest realistic distance for fish travel
 
Jon,

You could tackle it using a raster-based least-cost path analysis as was
suggested. For that you will need a data layer at the appropriate resolution
to serve as a cost surface. I would expect it to contain at least
bathymetry, but possibly other variables as well, depending on what the
critter considers a more or less costly way to move (e.g. seagrass density,
currents, etc.).

If you had a network of origins and destinations, you could approach it as a
shortest-path network problem. The only R module I'm familiar with for
network analysis is igraph, which I have used to calculate the shortest
(topological) path from point 1 to point 2 within a network graph.

Alisa.

On Thu, Dec 18, 2008 at 2:38 PM, Jon Loehrke <jloehrke at umassd.edu> 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.
>
> 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
>
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo at stat.math.ethz.ch
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>
>


--
Alisa Coffin, PhD. Candidate
Department of Geography
University of Florida
Gainesville, FL  32611

        [[alternative HTML version deleted]]

_______________________________________________
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shortest realistic distance for fish travel

Michael Sumner
In reply to this post by Jon Loehrke
A vaguely similar approach is provided by the (hard to use) code in the
tripEstimation package.

This package is primarily for determining realistic track locations from
raw archival light data or satellite locations with estimates included for
the "intermediate path" between data collection times, but the methods used
to apply auxiliary data such as SST or bathymetry, and simple speed models
could be applied to your case.

I'd be happy to try an example to see if the existing code can be applied,
although it might be a bit heavy handed.

Is there a freely available coastline data set that you would be confident
using in your case? Is the GSHHS sufficient? Do you have other data that
can be used to limit the likely/possible path?

Some more context for the package via an (out of date) light example can be
found here:
http://staff.acecrc.org.au/~mdsumner/Rutas/tripEstimation-demo.pdf

Cheers, Mike.





--On Thursday, 18 December 2008 2:38 PM -0500 Jon Loehrke
<jloehrke at umassd.edu> 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.
>
> 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
>
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo at stat.math.ethz.ch
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo