When I create a flow length analysis, and use identify tool on a cell in the layer, it just shows "stretched value" and "pixel value" I don't understand how it's supposed to show length. I'm using ARCGIS (ARCMAP) current version.

  • Please expand a bit on what you're doing in a "flow length analysis." What command(s) created the "layer" you are inspecting? – whuber Mar 7 '15 at 19:44
  • The Flow Length tool is in Spatial Analyst/Hydrology. Once it is calculated, the output is nearly identical to Flow Accumulation Raster, but when you use the Identity tool on cells, it displays "Pixel Value", which is the distance (in pixels) that that line of flow travels (upstream or downstream depending on which you chose). Now I've noticed that the Flow Accumulation and Flow length rasters show that the cell size is 2.99 and if I divide a pixel value by that I get the approx. distance. I'd just like to display distance straight from the Identity tool without having to calculate it myself. – StreamSide Mar 7 '15 at 19:57
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    The help doc for the Flow Length tool states, "For each cell in the output raster, the result will be the number of cells that flow into it", which I'm assuming is a typo because that would be the case for flow accumulation. Regardless, it does indicate that you're right that the output value is in grid cells. If this is the case, then you need to multiply (not divide) the raster by the grid cell size to get the length in map units rather than grid cells. However, this only approximates the length, since the distance between diagonal neighbours is greater. I'm surprised they did it this way. – WhiteboxDev Mar 8 '15 at 14:25

Stretched value is the rendered value. That is how it looks on the screen. Pixel value is the real value that the pixel represents. The latter is probably what most people are after.

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