Merging LIDAR DEM Surfaces - Paste surfaces not available

[Anonymous]

Let me preface this by saying my Civil 3D skills are a little rusty.

I am trying to build a surface to export to HEC-RAS.  I downloaded DEM (GeoTIFF) from our state's LIDAR library, and for what I need to do, need four "tiles" of data.  All four imported into a grid surface very nicely, but they came in as individual surfaces, which was a problem when sampling cross sections.  I created a new surface, with the intent to paste all four into it, but pasting surfaces wasn't even an available option under Definition > Edit.  Does anyone know what could be causing this, or another way to merge all four "tiles" into one?  Two of the "tiles" as downloaded from the library are attached for reference.

Horizontal datum is CT83F.

[Udo_Huebner · Accepted solution]

Option 1: You create a new empty surface with the command: CREATESURFACE and insert all 4 DEM files with the command: ADDSURFACEDEMFILE.
Option 2: You create a new empty surface with the command: CREATESURFACE and insert all existing surfaces with the command: EDITSURFACEPASTE.
This works fine for me with the uploaded DEM(Geotiff) files. No Problem when pasting Surfaces.

[Pointdump · Accepted solution]

Joseph,
I don't think you can paste Grid Surfaces. (I might be wrong)
I grabbed the other 2 tiles and created 4 Tin Surfaces. I was able to paste them together, but it still shows the Boundaries of the individual surfaces. I don't know what to make of that.

Dave

[Anonymous]

Thank you, Udo, that worked!

[Anonymous]

Thanks, Dave.  I tried it this way, as well, and that also worked.  The boundary wasn't an issue in exporting to HEC-RAS, and I was able to export the surface there and accomplish what I needed to.