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Path distance tool: uphill path

Question asked by cheburashka on Feb 4, 2015
Latest reply on Jul 4, 2015 by Dan_Patterson

Hi,

 

I am new to ArcGIS and would really appreciate your help understanding how to work the Path Distance tool. I have read the documentation and thought that I understood how the vertical and horizontal factors work, but I was wrong.

 

I would like to calculate the distance for the shortest uphill path to a "source" for each point in the raster. That is, we can only move uphill or flat - we can not go downhill.

 

To do so, I'm using the Path Distance tool in the Spatial Analyst in ArcMap. Here are the parameters that I've been setting:

 

input raster: just a single point that i created in a shapefile - this is my "source" - the tiny blue dot on the image below

input cost raster: nothingdem+point.jpg

input surface raster: dem (the image is to the right, and the blue point is my "source")

horizontal factor parameters: binary horizontal factor; zero factor = 1; cut angle = 180 (i don't care about the horizontal factor, so I want it to be able to move as it wants)

vertical factor parameters:

input vertical raster: dem

vertical factor: binary

zero factor: 1

low cut angle: 0 (because I don't want it to be able to go downhill)

high cut angle: 90 (steep angle is not the problem, as long as we're going up)

 

output.jpg

When I run the tool, the output I get is not at all what I expect. I am attaching that here as well (to the left). I don't expect this symmetry, since the point is located on the slope. I expect all locations uphill of it to not have a path, so there shouldn't even be any distances.

 

 

Please help me understand what parameters I am setting wrong.

Any input is much appreciated!

Thanks a lot.

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