HEC-RAS / Civil 3D Connection Floodplain Mapping Issue

[ltmullen]

I'm trying to follow this video (http://au.autodesk.com/au-online/classes-on-demand/class-catalog/2011/autocad-civil-3d/floating-away...) to use HEC-RAS and Civil 3D to map out a floodplain based on the results of a HEC-RAS simulation.

I'm getting stuck at the part where he uses SAGA to import the geotiff...when I try to pull in the geotiff, I don't see anything at all in my window, and when I export to a .flt, based on the header file that I get, it seems that the coordinates of the lower left hand corner of the .flt are (0, 0), which isn't right.

Does anyone have any experience with the process described in this video?

Thanks!

[ltmullen]

Well, I got it to work.

It seems that the surface I was trying to export was just a little too big for AutoCAD to export, because when I recreated the surface (the original surface was created from GIS data, so I just created the surface again from the same GIS data with a smaller crossing polygon) and tried to export it, it worked fine.

So I'm good for now. Still, this seems to be a kind of annoying thing...I could forsee a case where I wouldn't have an option to make the surface small enough if I'm trying to model a portion of a river that's long enough. Is there any good way to patch two GEOTIFFs or two .flt files together?