Lowered & flat regions not cooperate with evevation data


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Hi Folks! I need some advice.


I have a house plan and a 5.3 acre lot that I am trying to combine. I had a digital survey done of the lot and created a plan of the lot using the survey pin location for the perimeter and imported the remaining  elevation data which is in the form of a set of X,Y,Z coordinates on a grid about ever 50 feet. I added features to the lot plan like the approved drain field, water well locations and a partially completed driveway already on the lot. That looks great. I then selected everything on that plan and copied it and pasted into a copy of the house plan, getting the position as I wanted it before deselecting the pasted lot plan. That all worked well and looked good.


Now I want to create a 'lowered region' to allow the access to a walkout basement. That did not look so good. I added a 'flat region' inside the lowered region. That looked better but the court outside the basement was under the dirt. So I added a terrain hole under the court. That seemed to get most of the result I was looking for but it was painful. That is because you can specify the height of the 'lowered region' but that is relative to the elevation of the geometric center of the region which changes every time you adjust its perimeter. That make it fun to fine a shape that emerged level with an existing contour line at the depth of the basement court. That was a pain but not the real issue.  


I have attached an image of a portion of the empty lot plan and that same portion of the plan that includes the house. Also a perspective view of the mess that resulted to help with the description below.


The contour lines generated by and between the two regions is ill-behaved. There are twists and turns, davits  and bulges that look horrible.  I think the problem relates to elevation data points within the regions confusing the math. What I have now is the best I could get with much experimenting. Is there a better way to get a smooth result?  I don't think I want to deleted the elevation points within these regions as I believe it would affect the lot's correct contour lines. Is there a way to have these regions ignore the elevation point within them?

Also the contour lines bend at the intersection with the house even though the regions extend under the house. I just have no idea why...


Is there a better way to accomplish this? Can the elevation points that created the lot be converted to actual contour lines that can be edited or at least cooperate with the lowered/flat region tools? Any help I can get would be greatly appreciated.


Plan of lot before adding to house plan.jpg

Plan with low, flat reagon problem.jpg

Perspective view with low, flat reagon problem.jpg

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  • 5 weeks later...

Thank You katalyst777. By following your lead, I did get the result I wanted. I traced over the contour lines generated by the imported elevation data around the area of interest with temporary CAD lines. Then deleted all elevation points within the area and traced over the CAD lines with my own contour lines. That restored most of the elevation outside where I wanted to make modifications.  I then defined contour lines the way I wanted them to be within the protected area to create the lower area for the walkout basement. Using many contours lines (for ever foot change) prevented the terrain generator going nuts propagating overshoots and undershoots. Note: I also discovered that if you have turned on the 'flatten pad' option it will modify anything you try to do near the building. Thanks again.

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