I was recently contracted as a designer on a low impact design, 200-acre subdivision development with open ditch drainage and pertinent utilities. The intent was to take advantage of the natural drainage patterns of the property, as much as possible, and keep lot grading to a minimum.
As you might guess, delineating drainage areas was critical to the design but we were not able to perform this analysis using Civil 3D 2011 in any reasonable amount of time. Ultimately, another program was used to perform the analysis.
- The original surface was created using the property boundary as a data clip boundary and then adding an 800,000 point LiDAR text file. (The points were NOT imported into the drawing.) By defining the data clip boundary first the surface properties indicated only 90,000 points were used from the LiDAR file.
- A data shortcut was created from the surface and the drawing saved as a base surface drawing. The surface shortcut was then referenced into a new drawing and the drawing saved as a design drawing.
- Efforts to generate the watershed sub-areas in the design drawing were abandoned after several hours. Attempts to generate surface slope arrows were also abandoned for the same reason.
- As a check, I attempted the analysis on another, albeit, smaller surface. The program quickly created watershed sub-areas and slope arrows.
- Smoothing was applied to the referenced surface but both analysis methods again failed.
- Surface simplification was applied in addition to the surface smoothing and again both analysis methods failed.
- Surface simplification only was applied and again both analysis methods failed.
I posted this issue on the Autodesk Civil 3D Discussion Group but without response from Autodesk. I thought their policy allowed for some interaction on user posts but I could be wrong. One user successfully generated sub-areas from similar data but it took almost eleven hours.
This concerns me as more and more of my clients are attempting to use sonar, lidar, and laser-scanned point clouds in the design process. I am now a man on a mission.
Windows 7 (Ultimate 64)
AMD Phenom X2 550 Processor @ 3.10 GHz
ATI Radeon HD 5700 Series
8 GB RAM
AutoCAD Civil 3D 2011 (64)