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I am trying to come up with the best process for identifying aerial sewer lines (typically over streams) using the pipe inverts and a LiDAR-derived DEM. In other words, locate the lines where the Z value is greater than the elevation of the DEM. I came up with the following workflow that involved converting the sewer lines to points and comparing the Z value of each point to the associated (=extract values to points) DEM elevation, which resulted in identifying SOME of the aerial lines, but many were missed and I am looking for a "best practice" workflow.

A colleague has suggested the various tools from the hydrology toolset: flow distance, slope/aspect, flow direction, then flow accumulation.

I am also curious if anyone out there has some ideas about to identify aerial sewer lines using the pipe inverts and DEM.

DEM - exaggerated symbology to show elevation changes.

enter image description here

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  • Do you want to see the properties of the DEM or an image of the DEM itself?
    – slowe
    Jan 17 at 18:56
  • 1
    Uploaded images. I exaggerated the colors of the DEM to show elevation changes at the point of crossing.
    – slowe
    Jan 19 at 12:53

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