AutoCAD Civil 3D

[#1]

I have a contour map that i need to flip all the postive contours to negitive. So the Z cordinate for example is Elv 40 now i need to invert it to -40. I want to do this to the whole large contour map. ????

Shawn

[#2]

Hi,

set the UCS to look from the right side (or from front) and then mirror your contours.

- alfred -

[#3]

is it contour data or contours representing a TIN/DEM?

If its contours as CAD objects, you could use the Map3D side of C3D to perform a drawing query to multiply all contours by a (-1) value and then recreate the surface.  

I'm not a fan of surfaces from contours w/o the breaklines.  The software has gotten better, but there's still a loss.

The miserable brute-force way would be to export to xml and then replace the elevations with a "-" character.  dunno even where to approach that 

[#4]

Thank you, i will give that a try.

[#5 · Accepted solution]

Create a surface from the contours (do all the minimizing flat area options, you can read why HERE) if it's not already a surface. Create a flat surface at elevation 0 that's totally encompasses your surface. Create a volume surface that compares your surface as the base surface and the 0 surface as the comparison surface. Have the volume surface display contours. Extract the contours from the surface (if you don't want to have the surface).

[#6]

Thank you so much, that worked.

Shawn

[#7]

Guess I was having a "blonde moment" when I didn't think of that one ealier - nice!

[#8]

It's a technique I used to use in LDT to help delineate watershed boundaries, create an inverted surface and use the water drop tool on it.