I am working with the 10m DEMs and see some round depressions in Texas. I found this in two areas of about 12 sq km but do not have the tiles for the areas in between, so the area where I see this could be much larger. It is more or less at lat 33-34 and long 110-111.

The DEMs look like swiss cheese and the depressions have diameters between 500 and 3000m and the difference in depth between the edge of the depression and the deepest point is about 10-20m.

Is this a problem of these DEMs or do structures like that exist in Texas?

  • Where did you get the data? Do these depressions occur at the location of military bases? – Vince Apr 18 '15 at 13:57
  • It is the NED data, I downloaded it from the geospatial gateway last week. I do not know about military bases, but they do not really look like man made depressions, as they have different sizes and are irregular. – Iced_ Apr 18 '15 at 14:02
  • can you give more specific coordinates? lat 33-34 and long 110-111 is a box in arizona... – mr.adam Apr 18 '15 at 18:21
  • Sorry, I made a mistake with the coordinates. – Iced_ Apr 18 '15 at 19:35
  • Made a mistake with the coordinates. I have exact coordinates for a transect in the northern part. I did not find the degree symbol ... Transect 1: Point 1: 101 dg 47 min and 35 dg 11 min; Point 2: 101 dg 35 min and 35 dg 22 min. Transect 2: 102 dg 43 min and 33 dg 45 min; Point 2: 101 dg 37 min and 33 dg. The name of some counties where I found this is: Hockley, Randall, Armstrong, Carso – Iced_ Apr 18 '15 at 19:45

Without seeing specific screenshot examples of what you are seeing, based on research I would say yes, the DEMs are fine and those structures do exist.

I pulled up Google Maps and took a look at the terrain and satellite imagery from some of the counties you list. Armstrong shows them with the greatest frequency and proximity, for example at https://www.google.com/maps/@35.077517,-101.6107598,17058m/data=!3m1!1e3!5m1!1e4

They appear to be related to agricultural use. The depressions look to be water collection/storage for irrigation purposes. In some cases, particularly examples seen in Randall Co, you'll find them at the center of radially plowed fields using center pivot irrigation systems. Give the arid nature of that part of the country, I can easily see them being made to collect both rainwater when it falls as well as recapture irrigation runoff. They may also start off as natural depressions that are further 'enhanced' by agricultural use.

You might try adding an imagery basemap layer to your map/project, or grabbing some NAIP imagery from the same location to verify/confirm you're looking at the same things.

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