topic Re: Issue finding length of stream from Flow length tool in ArcGIS Spatial Analyst Questions

Issue finding length of stream from Flow length tool

JoshDawe — Mon, 25 Sep 2023 18:30:38 GMT

Hello everyone,

I am using Arcmap 10.8.2 and trying to find the length of my longest stream in a watershed using the flow length tool. When I run the flow length tool it gives me a result in degrees, and I need it in metric.

When I open Arcmap I first right click on the layers and change the coordinate system to a PCS. Then I bring in my digital elevation model, but it seems the DEM is still operating in a GCS. Any idea what I could be doing wrong?

Thanks Josh

Re: Issue finding length of stream from Flow length tool

JakeSkinner — Mon, 25 Sep 2023 18:35:47 GMT

Hi @JoshDawe ,

Try setting the Output Coordinate System to the PCS in the Environments of the tool:

Re: Issue finding length of stream from Flow length tool

JoshDawe — Mon, 16 Oct 2023 10:17:12 GMT

Hello @JakeSkinner thank you for the suggestion. It worked and I was getting meters.

In case anyone else comes across this post there was another issue.
When I used Clip (which is under Data Management tools>Raster>Raster Processing) I didn't have the "Use input features for clipping geometry" checked. I needed to check this in order to clip my data to just my water shed. When it was left unchecked my data clipped to a simple rectangle around my water shed which was giving me a longer length on my main channel.