I often have to do storm pond surfaces that (for the purposes of planning) are flat on the bottom. These surfaces are created from a combination of survey data and grading groups and the tin of these surfaces is perfectably acceptable. However, when contours are shown, the flat bottom is shown with contours jig-jagging all over the place.
The attached image shows a comparison of the same pond. The top was created with survey data and grading groups; the bottom was created using contour data only. The generated surface on the top shows the bottom contour going in different directions and has parts where the an expected contour is missing.
Any ideas on how to correct/manipulate the surface to show a proper flat surface?
Solved! Go to Solution.
You might be able to get away with adding a point of two to the middle of the bottom that is 0.01 feet lower than your bottom contour. This might get rid of the flat area (that could be causing the "jig-jagging"), but it won't be low enough to change volumes or add an additional unwated contour line.
That clears up a lot of frustration. I was thinking I was missing an obscure setting, but this is a easy workaround. Many, many thanks!
Try this, under Prospector->Surfaces->(Your Surface)->Definition->Edits, if multiple edits exist, delete them one by one starting with the first listed (oldest). This will get rid of interpolations that C3D added as you created the surface, which may now be interfering with newer data and causing the weirdness. This has worked for me with similar looking surfaces.
Nevermind, you found a way while I was away from my desk!
I've come across a variation on this solution that will help with more complicated areas. Instead of just adding a point with a slightly lower elevation, consider offsetting the feature line of the toe of the slope and adjusting the elevation of that feature line by a small value. This helped fix my rather complicated/narrow flat area (whereas the point approach required many points to make the contours right...)
We had this same issue just now and after some out of the box thinking we found something that worked.
We were trying to grade to elevation 271.00 with 1' & 5' contours for surface display and the 271.00 contour was all wonky.
Edited the grading to 3 decimal places (270.999) and when the grading rebuilds, the surface contours are fine and showing a flat surface.
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