How do I derive slope from a very large DEM?

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04-29-2020 12:48 PM
by Anonymous User
Not applicable

Hi there, 

I'm trying to calculate slope based from a national DEM - USGS 3D Elevation Program (3DEP), found here: 3DEPElevation (ImageServer)  - and am having trouble with the spatial analyst geoprocessing tool given the size of the raster. When I try calculating slope in ArcMap Desktop, I get an error message saying that the file is too large. When I use ArcGIS Pro, it processes up to 5% and then stops. I'm using a VM, so bandwidth is not the issue. Does anyone have any tips on processing national DEMs? Or are there any pre-processed national slope files out there that I could download?

Thanks!

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5 Replies
JoeBorgione
MVP Esteemed Contributor

I ran into the same sort of problem recently trying to process just one county worth of imagery.  I cannot imagine the cpu and and memory (and probably graphics memory too) to complete a full country. Is there a way you can get the data into manageable chunks?

That should just about do it....
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by Anonymous User
Not applicable

All of the other DEMs that I've found are at county-level or similar, which would be a hassle to patch together at the end. Unfortunately, I need a national slope raster to conduct analyses!

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DanPatterson_Retired
MVP Esteemed Contributor

The page you posted suggests you can download the slope map itself, rather than calculating it.

JoeBorgione
MVP Esteemed Contributor

I just added the url to an arc pro session: not sure how to get the slope data out of it though...

I think I see where Dan lives....

That should just about do it....
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curtvprice
MVP Esteemed Contributor

Are you sure you need full resolution on this? Bandwidth may not be an issue, but processing zillions of cells with any neighborhood operator is just a LOT of data to process. Even if you downloaded tiles on the data it would take you weeks I'm sure.

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