topic DEM with file extension .adf contour error in AutoCAD Map 3D Forum

DEM with file extension .adf contour error

nathan_westhoff — Thu, 18 Apr 2019 13:58:04 GMT

Hello Everyone,

I am fairly new to the Map3d world as I usually work in mostly Civil 3d. Having said that this issue could fall into either the civil 3d or Map category.

I have downloaded DEM elevation data from the USGS site in ARCGRID format which gives me an .adf file that I bring into Civil 3d via the "Create Surface from DEM" command. The contours show up however the higher elevation contours seem to end and shoot into nowhere.

Is there an easy solution to fixing this issue? Am I doing something wrong.

Additionally the elevations are in meters. Is there an easy was to translate this?

Thanks ahead of time for your feedback. I have attached a zoomed in and zoomed out view of the surface.

Re: DEM with file extension .adf contour error

ChicagoLooper — Fri, 19 Apr 2019 00:33:17 GMT

The image titled 'zoomed in' clearly displays contours. What are those straight lines on (or beneath) the contours? They can't come from the DEM, or can they? Contour lines should never intersect but the curvy contours are definitely intersecting with the straight lines. And the DEM doesn't appear to be a rectangle. Can you explain why?

Re: DEM with file extension .adf contour error

nathan_westhoff — Fri, 19 Apr 2019 13:32:07 GMT

The straight lines are what I was wondering about, not sure what they are but they came in with the DEM file. It almost seems as if they are extensions of some of the contours that protrude into nowhere as you can see in the zoomed out image.

The DEM in not a rectangle because I data clipped the surface to improve performance. The whole surface acted in the same manner.

On a side note I downloaded this elevation data from USGS site and inserted it. I also downloaded some elevation files in .tif format from the USDA data gateway. I inserted that and it worked great. So I have gotten the data I need now but still curious as to what could cause this issue if I ever want to download elevation products(3DEP) in arcgrid format from the national map on the USGS site. The national map worked great for other items, just not the elevation data.

Thanks for looking into it.