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Hi Geonet! I can't get an SRTM30 DEM to display in Arcmap properly, help?!

PatrickDonnelly1

Hi there, I am a 3rd year university student doing geography. For my dissertation I am doing flood risks in Kenya, and for it I need a DEM. I found a really good one here: Index of /srtm/version2_1/SRTM30/e020n40 but whenever I try and open it in ArcMap it just says "invalid raster data set, failed to create raster"

Does anybody know a way around this? or maybe just a different DEM? I need it in as high resolution as possible for the city of Mombasa.

Thank you in advance!

Patrick.

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IanMurray

Patrick I would use a different/better dataset then the one you are currently trying to convert. I suggest checking USGS Earth Explorer, I found 30m dem for Mombasa there in the Digital Elevation/ASTER Global DEM. If you make an account, it should be free to download in GeoTIFF format. (I believe, its been a while since I used it).

Curtis Price‌, got any other suggestions?

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IanMurray

Hi Patrick

USGS DEM files (.dem extension) cannot be brought directly in to ArcGIS, they must be converted to another raster format first. Try using the ArcGIS Geoprocessing tool DEM to Raster to convert to your desired file type(see help below). The converted raster should open no problem.

ArcGIS Help 10.1

PatrickDonnelly1

Thanks for the reply Ian. Unfortunately that hasn't worked, and its given me Error: 010067: Error in executing grid expression.

Ive heard a fix for this may be to run processes in the "foreground"? But I have no idea what that means.

Any help is much appreciated!

RichNauman

You can try the Esri Terrain Service (http://www.arcgis.com/home/item.html?id=58a541efc59545e6b7137f961d7de883 ).

We just updated it with 30 meter data for Africa.

Rich Nauman

PatrickDonnelly1

Thanks Rich, I'm probably just being very stupid but I can't seem to find any kind of a link there to download a DTM/DEM for Kenya. Is there any chance you could more directly link me? Or maybe an absolute-idiots-guide to downloading it?

Thanks very much for your help.

IanMurray

Curtis Price‌, got any other suggestions?

RichNauman

Patrick,

One nice feature of GIS services is that you eliminate the download step. Its a different way of thinking about GIS but a very powerful way of doing things.

Go to the content item (the ArcGIS.com webpage) for terrain and click the blue drop down box that says "Open" and the select "Open in ArcGIS for Desktop". Your browser will save a file called item.pitem to your default downloads folder. Double click that file to open in desktop. From there the service will behave just like data on your disk. You can use it as an input to Geoprocessing Tools, Model Builder, or Python Scripts. If you really want a local copy you could run the clip tool or export the data to a new raster. There is an area limit and i can't remember it right now but it should work. The 30 m Africa data was just recently released by the USGS and NGA so it should be the best available.

PatrickDonnelly1

Hi guys,

Sorry for the absence I was excitedly storming ahead.

I was able to obtain two ASTER tiles which show mombasa (and indeed all of the kenyan coast!) in 30m resolution from the Earth Explorer website. I Merged them using the mosaic function.

Thank you all for your help, very much appreciated!

I am sure I will be asking more questions soon!

Patrick.

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