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I build corridors between core forests using the Linkage mapper (https://circuitscape.org/linkagemapper/). For inputs i used core forest (Polygon file) and resistance raster as 1 (uniform resistance with value 1). Euclidean tool was used for network adjacency method. I also limited the maximum distance between core forests for corridors as 20 Km meaning forests farther than 20 Km will have no corrdiors. With these specifications, the tool was run and the results for corridors were obtained.

But i have difficulty understanding the final raster values of the corridors obtained in corridor.gdb.

What are those values in the raster file and how did the tool reach to the result?

I am attaching the screen shot of the output file with corridor raster along with LCP(least cost path marked as red).

The values of corridors are bit strange and why is it so?

Could someone help me in explaining the image?

The LM2903_corrdiors is the final output image with values called the normalised least cost corrdior value which is equal to Cost weighted distance from core forest (a) + Cost weighted distance from core forest (b)-Least cost distance when moved along the ideal path. (I made the symbology such that values greater than 5000 m gets no colour). I found this equation from the guidelines which i didn't understand completely. The marked red line is the least cost path and takes a strange shape even when the resistance is uniform.

Why is it so?

Corridor raster with least cost path

closed as too broad by PolyGeo Jun 15 at 8:42

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I checked the python script and looked for a proper manual without success.

You could try fiddling with each individual parameter and observing the output.

The legend you provide is probably the default one, and is not very clear.

You could inspect the attribute table to see what the histogram says.

The grey corridor looks like the max distance between polygons without exceeding the 20 km distance. On the other hand the LCP looks alright to me, it wont be a straight line because you have a resistance raster (cells, hence a diagonal is not possible).

  • The LM2903_corridors is the output raster file from value 0 to 233668 and i think the values in this raster file are called normalized least cost corridor values. I made the symbology such that normalized least cost corridor values greater than 5Km is hollow or no colour. As per the guidelines this is obtained from the formulae: Cost weighted distance from core area (a)+ Cost weighted distance from core area(b) - Least cost distance accumlated along the ideal path (connecting the core areas).I gave uniform resistance to all the places and why do you think it cant be a straight line? – Maya Nov 19 '18 at 9:57
  • I believe this has to do with the cell size value of the resistance raster. If possible try to use a 4 times smaller cell size value for the resistance raster ( I am not talking about changing the resistance value, just the size of the cell ). The result after running the process will be self explanatory. If I am on the right track, the result should be smoother. – Roberto Zeeland Nov 19 '18 at 15:28

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