TheSwamp
CAD Forums => Vertically Challenged => Land Lubber / Geographically Positioned => Topic started by: drizzt on September 24, 2008, 03:24:15 PM
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Is there a way to find the intersection between two surfaces. I have a site that was graded to high on one end, and not high enough on the other. I need to find out where they need to take down the grading that is to high at. They aren't going to wory about where it is to low at, except where the push the high dirt in.
So, I am thinking I need to find the intersection between the two surfaces.
I am using LDT 2007 with civil design and survey add ons.
Thank you in advance for your help
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Short answer is to use a Volume Surface.
The tools you need are in the Terrain menu. First, create a Site in Site Definition -> Define Site. Then create a "Stratum" that specifies your two surfaces. Then perform a volume calculation on the "Stratum". Once you have a Volume surface, use it to create contours, and the 0 contour is the line where the surfaces intersect.
(this is something that is much easier in Civil-3D, btw....)
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yeah I know, I am still begging for c3d though, let me give this a try and I will let you know if I got what you are saying..
thanks again
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wow, that's pretty sharp...
Thank you
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Me thinks whomever did the design on this site would do well to revise their design procedures. There is a process that I teach that prevents exactly this type of design error from ever happening in the first place.
Here are the Letters of the Method:
L = Limits of Construction or Grading is established tying in to Existing Ground
P = Pad elevations are established
P = Paving is designed based on the pads (Do NOT even think of using TOP of Curb as the design criteria, as once you establish your pads and paving the TC takes care of itself.
P = Ponds are added as required.
Pretty much if one follows this procedure, the site practically designs itself, and the number of revisions and or iterations to a get a grading design to work is reduced greatly. I think that I have posted a few examples of this type of grading method here.
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Man I wish I could watch you over your shoulder designing out from your pads just once. I haven't yet figured that out completely yet. Didn't you say you just use the grading tools?
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yes, grading features and feature lines.....the path to happiness.
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I could see how you would grade out from the building to the sidewalk and then to the eop, and even into the drive aisles, but I'm not sure how you deal with islands, curves, angles, etc. within and/or beyond the sidewalk adjacent to the bldg.
Any hints?
Sorry for the thread hijack...
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I could see how you would grade out from the building to the sidewalk and then to the eop, and even into the drive aisles, but I'm not sure how you deal with islands, curves, angles, etc. within and/or beyond the sidewalk adjacent to the bldg.
Any hints?
Sorry for the thread hijack...
A sample of this is on the PIRATE 3D DVDs
feature lines, grading objects and infills.......one happy grading group ;-)
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Can't wait for that to be released.
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mmmmmm...dunno.....12D can do that in 2 secs........"intersect 2 tins"....okay...I'll shut up now.......
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Only problem with that Alan is that drizzt is using LDT w/CD instead of 12D. Otherwise you might be able to increase his efficiency with this issue.
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mmmmmm...dunno.....12D can do that in 2 secs........"intersect 2 tins"....okay...I'll shut up now.......
Yeah, the Civil-3D version is "Create a Volume Surface, select Base and Comparison Surfaces".
Or if you don't actually need a Volume Surface and just want a volume report, go to Surfaces->Utilities->Volumes and simply pick the Base and Comparison Surfaces.
But Land Desktop makes you gather a crowd, perform a jig, and pass around the collection jar before you get a volume. :grazy:
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Short answer is to use a Volume Surface.
The tools you need are in the Terrain menu. First, create a Site in Site Definition -> Define Site. Then create a "Stratum" that specifies your two surfaces. Then perform a volume calculation on the "Stratum". Once you have a Volume surface, use it to create contours, and the 0 contour is the line where the surfaces intersect.
(this is something that is much easier in Civil-3D, btw....)
0 contour? This confuseth me. How would you get the line of intersection in your dwg (in Civil 3d)? It's not necessarily going to be the 0 contour unless I'm not thinking of something?
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When 2 surfaces are defined over the same horizontal space, if you compare the 2 you will have cut and/or fill between them. Where there is neither cut nor fill, is where they intersect. This is the 0 contour of the Volume surface, since fill would be negative contours and cut would be positive.
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Yes I have just noticed. This is the first time I've tried it as I've only done volumes a few times and I always just compared my eg and fg surfaces rather than creating a volume surface so I'm a little "green" in this area.
Thanks Jeff.