Two breaklines at same elevation. Large Gap between. Contour zig-zag btwn.

[doni49]

I'm finally at the end of the grading work for this lake regrading project.  But I've got one issue left that I'm stumped on.

In the following image, you'll see three breaklines set @ 822.  There is a rather large gap between them (this is supposed to be FLAT.  But the 822 contour is doing a zig-zag back and forth between the breaklines.  Since the breaklines are AT 822, why won't the 822 contour just follow the breaklines around?  The second image is the same area showing the triangles.  I snapped at the ends of all the triangles in the area and both ends of each triangle are at 822.

[Neilw_05]

Those little anomalies are common with TINs. Try adding a few points or breaklines that are slightly higher or lower than the contour to that area.

[doni49]

I've continued to troubleshoot this and have found something that I think is at least PARTIALLY responsible for this.

This is a man-made lake that's being regraded.  In the first image, you'll see a "top of bank" closed polyline that goes around the lake.  Then you'll see a Bottom of Shoreline Slope (Green) that also goes around the lake.  The Bottom of Slope is at 822. 

Then there's another closed polyline (black) that goes around the lake INSDE of the shoreline.  This is also at 822.  The surface is FLAT between these two.

That all works fine until I add my jettys.

One jetty will result in the 822 needing to split off on both sides of it.

The bottom of each jetty is at 822 until it hits that black breakline.  Once inside that breakline, the bottom of the jetty follows the EG surface.

The second image shows what I'm talking about there.  The red lines represent kind of what the 822 contour needs to do.  The blue line represents what the 821 contour looks like (to keep the breaklines clear, I've turned off the triangles and contours).  These images are of plot previews.

EDIT:  I've uploaded my files to dropbox.  This link will have a zip file containing two dwg files.  The one I'm working in is the DESIGN file the SURVEY file contains the EG surface which is d-ref'd into DESIGN.

https://www.dropbox.com/s/i5jzasy4wmm0la5/LakeGrading.zip

[Neilw_05]

I don't have time to look at your files right now but it seems obvious the jettys are causing a ripple in the triangulation. As a workaround you could try fitting the shoreline around the jettys.

[psi]

In your original post, just make the blue feature line at elevation 822.001 and the green one at elevation 821.999 and you should get the 822 contour at both. Trim them out of the Jetty grading areas so the feature lines don't interact with each other.

[doni49]

I'm having an impossible time trying to figure out how to get the 822 contour to split off in two directions and then re-join on the other side of the jetty.  Baiscally, I need the 822 contour to follow the bottom of the shoreline slope, hit the jetty and then follow the blue line around the lake then along the other side of the jetty back to the bottom of the shoreline slope.  AND have an 822 contour crossing in front of the jetty.

I know this is possilble in real life -- I'm just having trouble getting C3D to show it in plan form.  Imagine having a ditch where the top of ditch is 822 on both sides.  At both ends of the ditch, the 822 contour would split off and rejoin itself.

Edit:  Take a look at this please (it's about a minute long):

.

[rl_jackson]

Your TIN lines in the triangulation are too long, you need more points for this to behave correctly, look at the length of the triangulation within the lake itself, and try to replicate that, there is absolutely no way that the area can be a true elevation of 822 for the entire area just add some additional tin points and make them .01' higher or lower, and the problem will resolve itself.

[jmayo-EE]

Here's my 2 cents.

The tin algortithms have placed the tin lines incorrectly for this model and you have a horizontal plane modeled.

All of the tin lines that connect from elev 822 to elv 822 need to be swapped so there is a change in z accross the tin line.

Since this looks like existing/base map conditions I would tend to add the plines to the surface as contour objects vs breaklines (which I prefer if needed in design) making sure to enable the options in the Minimize Flat Areas By. I do this because it is much easier and more effective for a one shot base map condition.

In a design situation I would add the data as breaklines and add more breaklines to fix it. Swapping edges and adding points to the tin via surface edits can bloat the surface definition often with outdated edits. The breaklines give me a definitive object to edit in the model and minimize the surface definition. 

[jmayo-EE]

Oh forget my 2 ceents above. I read quickly and missed the same elev on BOTH breaklines. 😮

You need a high or low ridge in that area as already staed by smarter people than I. 😉

I would go with a the breakline for the reasons I did state.

[jmayo-EE]

... hmmm

I might simply try changing the elevation of the 822 breakline I do not want a contour on to something other than 822. 821.999 or 822.001

[Neilw_05]

The black line needs to move too. The blue and black would be parallel as they go around the jetty.

[Neilw_05]

I took a look at your files and spent a little time getting oriented and trying a few things but I don't have anymore time.

A couple of things I would try: Use gradings for the jettys and target the "EG after cleanup" surface. The grading will adapt to the transition from the flat cleanup area to the undisturbed area. One advantage to gradings is they have automatic/dynamic boundaries which might help eliminate anomalies at the boundary.

Also as was suggested, try adding the shoreline and cleanup polys as contours rather than breaklines.

If those modifications don't help, try extracting the 822 contour from Jetty#1 and use it to modify the 822 cleanup contour to make it wrap around the jetty.

Sorry I can't take more time to try this.

[doni49]

Thanks all.  I'll try importing the 822 shapes as contours (and removing from the surface defininition the breaklines that I've got) but it doesn't look too promising.  I just tried it in one area and although it was slightly better, it didn't fix the issue.

As to using Grading objects for the jetty, that's how I got the lines that I have.  But because of the corruption issues we've had in the past with grading objects, I exploded them down to polylines and got rid of the grading objects.

[doni49]

I just had a bit of an ephiphany.  As the surface "goes around the jetty", there would be TWO 822 contours--just close together..  Then the gap between them would widen.  I was trying to figure out how to get them to actually join at the jetty and then separate again.

[fcernst · Accepted solution]

You have crossing breaklines all over the place, coupled with contradictory data at the Jetty boundary..

[doni49]

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@fcernst wrote:

You have crossing breaklines all over the place, coupled with contradictory data at the Jetty boundary..

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Thanks.  I found the crossing breaklines issues when I started working on a method to ensure there are two 822 contours that can go around the jettys.

I've been uncrossing them for the past 30 min or so.

[fcernst]

No problem.

[doni49]

Once I got all the breaklines so they weren't crossing, the only zig-zags left are in the locations where the two are really close together.  I'm going to add a breakline down the middle between them at 822.0001.