DEM's from Terrain Nav

[sfore]

I exported 2 quad's from Terrain Navigator and toggled the 'Save DEM'.  My Terrain Nav coords were set to WV State Plane South Nad 83 before I exported my info.  I'm using C3D 2011.  I brought in the USGS maps and they landed where my .sid files are which is WV State Plane South Nad 83.

When I 'Create Surface From DEM', my surface area lands way north of my site...something like 2500 miles north.  I've never had any luck with dem's.  Any idea why my surface isn't landing where the usgs map is??

Shawn

[sfore]

Just to add...I also tried creating my DEM surface a different way.  I created a blank surface, then added the DEM file.  The dialog box shows the DEM file information as UTM zone 17 Horizontal Datum as NAD 27, Vertical Datum as NGVD 29 and units as meters.  I figure this is the problem with projection, but how can I get it to land in State Plane coords?

I also tried going thru MAPWSPACE to 'Add RasterImage and Surface Connection, and pick my .dem file, the green colored topo image comes in at the correct location, but with no contours.  Can I extract or create contours from this?  Please, what am I doing wrong????

Shawn

[sfore]

With the MAPWSPACE option I mentioned, I saw where I can create a contour layer (as polylines), but I would rather bring in a DEM as a C3D surface and in the correct location.  How can I get the DEM to come in coordinately correct (state plane)?

[david.zavislan]

Create a TIN surface and add the DEM file to it.  In the Add DEM file window you will be able to specify the coordinate system of the DEM file.  The DEM's point data will then be converted from the assigned coordinate system to the drawing's coordinate system.  This does not work with DEM surfaces.

[sfore]

It worked but not the way I thought it should.  My USGS map and DEM were exported out of Terrain Nav at WV SP NAD 83 South.  My drawing is set to the same.  First, I created my tin surface then added the DEM file and changed coords inside the DEM dialog to WV SP NAD 83 South and my surface still landed WAY north.  Then I tried same thing but changed coords inside DEM dialog to UTM NAD 83 - NAD 83/BLM 17N (ft us).  It landed somewhat in the correct spot but it was a little south (850'+/-) of my usgs map.  My USGS map shows a river; my contours were off a little from it.

See pic.  In the end, I changed my coords inside the DEM dialog to UTM NAD 27 - NAD 27/BLM 17N (ft us) and my surface landed correctly according to the USGS map I had previously brought in and the contours around the river matched the USGS.  The coords don't make sense, but it landed on top of the USGS and the contours are pretty close to what the USGS map shows.  Any idea why I had to change the DEM coords to NAD 27 inside the DEM dialog to get the contours shown correctly?  Something else that doesn't make sense is the DEM file info in the DEM dialog had the coords at UTM NAD 27 even though I exported it out of Terrain Nav st WV SP NAD 83. 

Thanks

[david.zavislan]

It appears that Terrain Navigator only exports DEM data in UTM NAD 27 coordinates.