I am working on the Precision Conservation Practice Siting Tools and have run my files through the Depression Identification Tool. Now, I am trying to go through each polygon to see which are true or artificial depressions and having trouble. How do I know which should be deleted?
Images from the user: The first image is of some depressions that appear to be the result of drainage ditches. The second image looks like it is a true depression. Do you think this is correct? Should the drainage ditches ones be deleted? I took a look at your images and I believe your interpretation is on track. That said, I have to wonder about your DEM. The very sharp angle and the interior polygons would suggest a very-high resolution DEM or maybe a DEM of poor quality? While I would expect some of those interior polygons…I call them ‘knots’…I think your images show a lot. I have attached an image below that shows depressions from a 3m DEM that has been conditioned somewhat. There is a tool in the ACPF>Utilities drawer that does some DEM conditioning that might be helpful. See DEM: pit fill / hole punch. Response: I did have 1m DEM, but I resampled to a 2m DEM as suggested and then used raster calc so that the Z-factor was in cm. Do you think these 'knots' are going to cause problems? Should I simplify the polygons?
- No, I don’t think they will cause problems…but it may be indicative of the quality of your elevation model. You may want to run the pit fill/hole punch tool on this and inspect the output. It may provide a better model…less bumpy. The result would likely be more regularly shaped depressions