Using DEMs with Civil 3D - Projection Differences? DEM Processing?

[Lisa_Pohlmeyer]

Need some projection help please.  I have a DEM file in *.adf format that I use to create a surface. I also have a deliverable of 3D polylines at elevation.  There's a consistent shift between the two.  The red contours are from the surface generated from the *.adf file, the white are the 3D polyline deliverables (product of the *.adf file)  I believe the product used to create the *.adf files was ArcGIS.

The projection information for the *.adf file is:

NAD_1983_StatePlane_Texas_Central_FIPS_4203_Feet

Projection: Lambert_Conformal_Conic

False_Easting: 2296583.33333333

False_Northing: 9842500.00000000

Central_Meridian: -100.33333333

Standard_Parallel_1: 30.11666667

Standard_Parallel_2: 31.88333333

Latitude_Of_Origin: 29.66666667

Linear Unit: Foot_US

Geographic Coordinate System: GCS_North_American_1983

Datum: D_North_American_1983

Prime Meridian: Greenwich

Angular Unit: Degree

The drawings are in State Plane: TX83-CF.  The reason for the shift is important and I want to know what Civil 3D is doing that it creates the surface in a different location than the software that generated the *.adf file.  Does Civil 3D process surface files differently?  Does anyone know what Civil 3D's actual process is for generating surfaces from these types of files? Are there assumptions made?

[Neilw_05]

One clue is the LIDAR data is in US feet whereas the state plane units is Int feet.

[Neilw_05]

I misread the state plane CS. It is US feet also. Sorry about that.

I'd inquire about the source of the state plane data. Was it reprojected from another CS? Who did it and how?

[silvernich]

Autodesk users,

I am running into the same problems for bringing in surface data.

Option 1 I bring in data as a GeoTIFF (while in Civil 3d > surface > definition > DEM files > .tif). This results in a shift in location when compared to bringing it into CAD via Data connect (while in Planning and Analysis > data > connect to data> Add to map).

Option 2 I bring in an ASCII file (while in Civil 3d > surface > definition > DEM files > .asc). This results in a stepped surface as noted in this blog: http://forum.civilsurveysolutions.com.au/viewtopic.php?f=6&t=357

My work around at the moment is using Global Mapper to make an ASCII file instead of using ArcGIS to make the ASCII file, then bringing it in (while in Civil 3d > surface > definition > DEM files > .asc) which does not removing the floating point values.

Is anyone else having similar problems? After troubleshooting this for some time, I am truly concerned about the best process to bring surface data from an ArcGIS .gdb file into CAD and have it be in the right place and not rounded to the nearest integer.

Any experience resolving this would be appreciated.

Thank you,

Nich

[clinton_merrell]

Try running MAPCSASSIGNNONE  then change the settings of your drawing to international feet, create your surface from the DEM, then reassign your CS using MAPCSASSIGN.   In Utah South State Plane, I've been having a shift of about 20 feet north to south for 3 years until I cam across this post:

https://forums.autodesk.com/t5/civil-3d-forum/dem-coming-in-shifted-ortho-image-comes-in-properly-wt...