I'm trying to work with raster data from this source: http://www.soest.hawaii.edu/coasts/data/maui/index.html

I downloaded the DEMs from different islands and imported them into ArcGIS. But I can't seem to do anything with them. First, I tried to merge the different DEMs into one new raster. I also can't calculate a viewshed from a known point. I constantly get errors from the like of "dem not valid".

How do I convert them into formats I can actually work with?

I'm not too familiar with raster datasets.

  • Could you perhaps send a screenshot of how the data presents in ArcMap? I cannot download the data from that link to view the data. What format is the DEM in? Are the DEMs projected, if so what projection is being used? – Keagan Allan Apr 17 at 22:19
  • Did the merge work or not? If not, what went wrong, and how were you trying to merge them? What format are they in originally? – Son of a Beach Apr 17 at 22:36
  • Please when you get an error, tell us what the error is exactly, don't just say something like "etc...". To do this, open the ArcMap Results window (Geoprocessing menu | Results), expand the failed result and right-click messages and select Copy, then paste into your question and use the {} button to format as code. Also, ESRI GRIDS are notoriously easy to corrupt by using Windows Explorer to move or rename them, if you've done something like this, edit your question to say so. – user2856 Apr 17 at 23:48

The DEMs are in NAD83 UTM Zone 4 (other islands) and Zone 5 (Hawaii). To mosaic all of them, you would need to reproject them to a common (not UTM) projected coordinate system. Might be easier to mosaic only the other islands and work with Hawaii separately.

They are in ESRI GRID format and work fine with the viewshed tool, I just ran one on the Maui DEM. Note, I couldn't get viewshed to run until I'd changed the current and scratch workspace environment settings to point at a folder instead of a file geodatabase.

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