Export to DEM Issues...
Anybody have any experience using the export to DEM functionality for surfaces?
My understanding is that it is supposed to use USGS dem format, but I'm having trouble getting the resulting dem to show up intact in ArcGis. The extents are off and it chopped off the northern half of the site...?
I think this is a Coordinate System issue, but can't figure out where I can change anything...
two screenshots attached. one shows surface in CAD, the other in GIS.
Thanks - I just tried that. Importing the DEM back into CAD does bring in the entire surface...
Hm. Any idea how well CAD has implemented the dem format? Maybe CAD can handle it, but arcGIS can't?
In your Civil may you export only to .DEM format, or others like .ASC or Geotiff ?
Seems like Arcgis can't decode well the .DEM one, so give a different try.
If it doesn't work, zip and attach it here, thx.
So... the geotiff only kinda worked. I can view and manipulate the exported geotiff image in GIS (ArcGis 9.3.1) which is helpful.
However, see attached screen shot for error/warning message received.
My drawing is in CA state plane and my exported geotiff is also in Ca state plane so there shouldn't have been any transformation issues... thoughts?
Has anybody ever successfully created a dem or geotiff that ends up with a CS that GIS recognizes?
Okay... get this. It works if I change the coordinate system of my drawing to CA state plane in meters (I was in feet earlier)...
Good to know... irritating, but as I've heard on this board before... there is always a work-around...
Hm.. I wonder if this fixes the originial issue I had with the export to dem command...
Still stuck on this. I can't get a dem (or a geoTiff) with the correct georeferencing.
so far the Export to DEM chops the surface weird (and produces weird errors in GIS) (My Original problem)
The geoTiff was promising.. but produces the error I linked to earlier.
If you change the CS in the dwg to State Plane meters, then GIS does not produce an error, BUT the surface is shifted (translated several meters to the west). screen shot attached shows original dem, and cad export.
This does not seem to be fixed even if I switch between survey feet or international feet . I've tried as many combinations of CS's, units, conversion factors, etc... to no avail... anybody?
I checked all my surface definitions to make sure I didn't accidentally move the surface to the west at some point...nope! This shift is occuring for different projects with different surfaces...
I read through some of the older posts on this dem export issue... sems like this has been an issue since 2009!
Has anybody figured out how to get AutoCAD to export a correctly referenced and intact dem or geotiff surface?
I'll figure this out yet...
The translational error depends on the distance from the origin. The attached images show two identical surfaces (as yellow borders) except that one is located near the origin and the other is way off to the northeast (coordinates of roughly 900,000,300,000 which are not unreasonable in a state plane coordinate system). With each surface I used the autocad command export to DEM and selected the geoTiff format. I then immediately created another surface from the exported gtif... Theses surfaces are shown as red borders. They are 'blocky' as you would expect with a DEM, but note the translational shift towards the origin... Is this a precision issue in CAD or a coordinate issue? projection issue? I could use some wisdom form the board on this.... I'm not sure where I need to look next for a solution to this...
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