What Is Chief Doing To Terrain?

[keithhe]

This terrain has proven difficult. I thought having the DWG for it would have made things easier, but not the case.

Can anyone explain what CA is seeing that I can't in its interpolation of this terrain? Specifically the rows of divets (very deep) it is adding automatically and nothing I can do to get rid of them. Nothing I've seen on a terrain before. See attached photo and plan.

Suggestions to "smooth" this terrain while keeping the overall slope nature of the lot?

Thanks,

Keith

Costa Rica Test.plan

[Mark3D]

Have a look at this i removed a lot of elavation data and it seem better but i may have removed to much but it will give you the idea

https://dl.dropboxusercontent.com/u/29819538/Costa%20Rica%20Test.plan

[keithhe]

Thanks Mark !! That looks a lot smoother.

I'm of the opinion that too much elevation data lines in CA just messes things up. Just always too choppy I find, but curiously sometimes I have fairly busy terrains with quite a few elevation lines that look fine, and smooth. If I can just figure out the right combination of elevation data and other parameters to make them all work.

[Joe_Carrick]

Less elevation data will always produce a smoother terrain.  Also consider some small (strategically placed) elevation regions which will tend to make smoother transitions from level to sloped areas.

[keithhe]

Thanks Joe. I'll do some strategic removal of elevation lines, as Mark did, which looks pretty good, and see what I can get. I think I will keep the lines, as non-elevation though, for any site work later, but not to generate terrain. Less is better.

[Bill_Emery]

There is some errant elevation data in the plan that I can't easily find.

 

I copied the elevation lines into a new plan, and everything looks good.

[keithhe]

Bill, you did this without removing any lines? From what I can see of the thumbnail, that looks great. Can you explain how you did that?

[Bill_Emery]

Here it is with no lines removed.  I may have missed a few lines.  It was my goal to avoid the gremlins.  There is some un-selectable elevation data that is affecting the topography; causing the divots.

 

[keithhe]

Bill,

I thought that some of the CAD import data may have been wrong, and checked lines in and around the divots (primarily the secondary contours) and could not find anything inconsistent with what should have been there. No other elevation data brought in, so no idea where the divots are coming from, although you got rid of them. Still not sure what you did ??

[Bill_Emery]

I'm not sure what I did, but it works.

 

I thought it was errant elevation data, but now I don't think that is the case.

 

I've done larger properties with steeper slopes without problem.  I usually use two foot contours, but will sometimes use five or even ten foot contours with larger properties.

 

There are some minor divots in this plan, but it's behaving much better that the original plan.  I notice it behaves much better when I use fewer contours although this plan has all of the contours active. 

metric topo 2.plan

[keithhe]

Thanks Bill !! No idea how you did this, as I could never get the oddities out of it. I have found that terrain is one of those difficult to understand features of CA, if you are trying to get a real world situation correct. Some of the things just don't do what you would expect. Must be a cake walk for the flatlanders.

[keithhe]

Just wanted to thank the guys that helped with this (Mark, Joe and Bill). Lots of good answers, so hard to pick anyone "best", as all helped.

[glennw]

Keith,

You have several Elevation Regions that are causing most of the problems.

There is one main culprit in the top left corner of the site and several down in the lower left.

 

The easiest way to delete them all is to select one, click the Match Properties tool, check Object Type (make sure it is an Elevation Region), OK.

This will select all (well, most of them) the Elevation Regions in the plan, hit Delete.

Rebuild the terrain.

 

There are other weird things going on with the plan as well - but the above is the main cause of your problems.

 

Here is a video:

 

http://screencast.com/t/IiVcGgbeI

[keithhe]

Glenn,

 

Curious as to how this may have happened. I added no terrain regions, and simply imported the CAD DWG that as far as I could tell only had the contour lines and the terrain perimeter. The rest, was I though text file related. I will go back and try what you say, but would never have occurred to me that somehow terrain "features" or regions were there. Great catch, and has me curious to figure out where it was coming from. 

 

Thank you sir, as this was really frustrating to see the odd things happening that normal interpolation between elevation lines should not have caused.

[glennw]

Keith,

 

The Elevation Regions were probably created automatically from closed polylines (contours).

That's all an Elevation Region is - a closed Elevation Line.

 

If you draw an closed Elevation Line (polyline) and open it's dbx, it is actually the Elevation Region dbx that opens - not the Elevation Line dbx.