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Overland Distance w/DEM

Anonymous User

Hello! I have a DEM and I have a road. The linear geometry has x and y values, but no z. How can I use the DEM to give me an accurate length of this mountainous road?

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OliverGinzler

With 3D Analyst:

3D Analyst Toolbar: Convert - Features to 3D; road as input; dem as source of heights

The result is polylineZ!

Download Easy Calculate 5.0 from: http://www.ian-ko.com/

Open the attribute table of the new polylineZ - create new (double) field - open the field calculator - load and run the "shape_Return3D_Length.cal"! Done

EricRice

Hello,

You don't have to convert the features to 3d and do the calculation with 3rd party tools. In ArcToolbox > 3D Analyst Tools > Functional Surface, run the tool called Surface Length. This calculates the surface length of each line in a feature class based on a raster or TIN surface. The surface length information is stored as an attribute of the input feature class. For your benefit, I'm including a link to How Surface Length works This will help you determine and understand how sampling distance impacts the length calculation.

If you're using ArcGIS 10, this tool is deprecated, and you will want to run the Add Surface Information tool.

Regards,
Eric

Anonymous User

Thank you for the input and the link. Each time I run the tool, it says it's 100% complete, but then it stops, does not close the progress window, and enters a "0" value into the feature class' attribute table for SLength. The line segment is entirely contained by the DEM, so I'm not sure what's wrong. Any thoughts?

OliverGinzler

Tried my suggestion?

Anonymous User

No; I work for a large, public institution where I am unable to download third party tools. Thank you for responding, though!

EricRice

Thank you for the input and the link. Each time I run the tool, it says it's 100% complete, but then it stops, does not close the progress window, and enters a "0" value into the feature class' attribute table for SLength. The line segment is entirely contained by the DEM, so I'm not sure what's wrong. Any thoughts?

Hi Marianne,

Are you using 9.3. or 10.0? Is the data in a projected coordinate system? Is the line and DEM in the same coordinate system? Note, they don't have to be the same, but it would be a bug if that was why it wasn't working. I've run the tools in both versions and they always complete for me. Is your line a shapefile, PGDB, FGDB, or SDE feature class?

Have you tried using other datasets, or making a simple 1 line feature class to test with on a small DEM?

NaZhang_Esri_0-1767820729460.png

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