Lowest of two surfaces

[joao.nuncio]

I need to define a surface made from two other tin surfaces that intersect each other.

The first surface is the current terrain shape, and the other is the purposed excavation work. The excavation work already has graded slopes, which extend further above the first surface. The excavation work surface was made from the concrete footings elevated platforms (it's from a building, not a road).

I need to either define the intersecting polyline (resulting from the intersection of the two surfaces), or a final surface with the final resulting terrain shape after excavation works.

I tried to paste both surfaces into a third one, but the graded slopes did not end at the intersection: the boundary of the second surfaces was not discarded as i wanted...

What else can i try?

Thanx in advance

[gandocadguy]

Did you paste your excavated surface after your existing surface? This order matters.

[joao.nuncio]

Thanks for the suggestion.

Yes I did try that: the inner area of the excavation surface turns out ok, but the outer area (which shouldn't exist) remains as well. Then at the boundary there is a vertical slope conecting that boundary to the existing terrain, and that shouldn't happen.

[gandocadguy]

What I would probably do is create a feature line around my excavation surface, add that to the existing surface, then paste. That feature line will ensure that the surfaces match.

[joao.nuncio]

What I would probably do is create a feature line around my excavation surface, add that to the existing surface, then paste. That feature line will ensure that the surfaces match.

How do i know where to draw that feature line? all i know is that the slope has a fixed grading, but i do not know where that slope will intersect the terrain.

[gandocadguy]

It sounds like you don't have a daylight feature. That maybe your problem. You can use a grading object to target your existing surface from your excavation. Then paste them. I didn't think of that sooner.

[joao.nuncio]

It sounds like you don't have a daylight feature. That maybe your problem. You can use a grading object to target your existing surface from your excavation. Then paste them. I didn't think of that sooner.

I guess i'l have to learn how to use that "daylight feature". Thanks for your suggestion.

I finally resolved the issue. I followed these steps after having both surfaces generated:

First I created a TIN VOLUME SURFACE out of the two surfaces. The resulting VOLUME SURFACE has, by definition, a contour line with 0.0 for elevation exactly at the intersection of the two surfaces. So I isolated that contour line by setting the minor and major contours to a value high enough so it will only show the 0.0 elevation contour line.

Next, while having only the "major contour lines visible", I exploded that TIN VOLUME SURFACE twice (once to become a block, e twice to become a polyline.

Now, I have the exact intersecting curve, so i add it to the excavation surface, triming any breakline that extends beyong this intersecting curve, There for having a surface corresponding to the inner part of the excavation works.

Finaly, the option to merge the two surfaces will now work correctly.

EUREKA!

Thanks for you help, gandocadguy

[brainman1000]

I guess i'l have to learn how to use that "daylight feature". Thanks for your suggestion.

I finally resolved the issue. I followed these steps after having both surfaces generated:

First I created a TIN VOLUME SURFACE out of the two surfaces. The resulting VOLUME SURFACE has, by definition, a contour line with 0.0 for elevation exactly at the intersection of the two surfaces. So I isolated that contour line by setting the minor and major contours to a value high enough so it will only show the 0.0 elevation contour line.

Next, while having only the "major contour lines visible", I exploded that TIN VOLUME SURFACE twice (once to become a block, e twice to become a polyline.

Now, I have the exact intersecting curve, so i add it to the excavation surface, triming any breakline that extends beyong this intersecting curve, There for having a surface corresponding to the inner part of the excavation works.

Finaly, the option to merge the two surfaces will now work correctly.

EUREKA!

Thanks for you help, gandocadguy

Instead of exploding the volume surface you could extract the contour line from the surface.