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boundnorth

importing survey info & converting contours

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I've imported a .dwg survey and am trying to create a site model. I've modified the property line, creating a polygon and have 'traced' the .dwg topo lines in a new layer to create polylines, which are then supposed to be able to be converted into 3D contours. I don't seem to be able to make this leap...

My questions:

1) There is an existing building and some existing retaining walls on the site which 'break' the line of the contours that intersect these foundations. I know that in VW the contours have to read as a continuous line so that they can be converted to polygons. Do I trace the contours around the footprint of the building (and the retaining walls) - which will basically stack them one on top of the other or can the program read the footprint created using the building shell/landscape wall tools and maintain the contour elevation as it moves around/through the building?

2) If the property line is drawn as a polygon, does the program read the contours lines as 'stopping' at the property line or does it read property boundary as the limit of the contour line - like the limit of work 'fence' in the grading menu. In addition, the surveyor did not do a complete topo survey of the site so some of the contours simply end where the tree line of a densely wooded area begins - are these lines that don't connect to the property boundary read as discontinuous lines?

Also, do I have to do something to prevent the the property line reading as one of the polygons to be converted into a contour line?

3) So, I have converted the polylines into polygons but when I try to convert 2D polygons into 3D contours, following the prompts to assign elevations and interval, none of the 2D polygons are highlighted in the drawing and basically nothing happens.

Any suggestions? Long blab, I know but I've hit a wall.

Thanks.

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Select all of the polylines and the use MODIFY>CONVERT TO POLYGONS. Then select the resulting polygons and use AEC>SURVEY INPUT>2d POLYS TO 3D CONTOURS.

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Further reading of your post, further answers:

1) You can do it either way. It mostly depends on what you need to show/do. One caution: make absolutely sure that none of the poly's (contours) touch or overlap each other, and that there are no "inside-out" vertices in any one of them.

2) The site model will be created to the edge of any/all of the original contours. You can then "edit group" and add a polygon to define the "edge" of the model. Make sure to UPDATE the site model to see any changes...

3) Make sure that you have POLYGONS (not polylines) to start with.

Hope that helps...

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Thanks for your reply... More questions re: integrating the elevations of the building footprint and foundation with the contour lines - I'm still not understanding the logic behind how it works. It sounds like I have to make the contours run into the footprint and interact with it because otherwise I will have to draw them on top of one another, which won't read.

Would it be possible to give a simple step by step road map - ie, do I set up the building footprint polygon before re-drawing the existing .dwg contours as polylines and converting them to polygons? Is there a specific way that the contour polylines/polygons have to intersect (snap to?) the building footprint polygon? Is the building footprint altered or impacted by the command to convert polyline to polygons?

Thanks. I'm really trying to get my head around the difference between contours as line (hand drawing) and contours as surfaces (VW) - I need to understand how it works in order to think through any given problem.

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Okay, basically what VW's wants is for you to create a Site Model and then use SITE MODIFIERS (eg: Pads, Fences, Graders) to alter the SITE MODEL, much like you would do in the field. For example, when you place a PAD w/ FENCE on a SITE MODEL, you set the elevation and slope (if any) of the PAD, then select the SITE MODEL and click UPDATE (in the Object Info Palette, AKA: OIP) the SITE MODEL will change to show the PAD. You can find the How-To's you're looking for in VW's HELP. Just look (or search) for SITE MODEL...

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But Peter, as you and I know, what VW wants us to do and what the program can really produce are two different things.

Boundnorth - you will find that the more complex your dtm and site modifiers are, that the VW site model will not produce accurate enough answers. Many times, I have found it necessary to redraw contours to get the required solution.

Sorry VW, but even tech support can not make the program do what is needed in a complex situation. I know you are trying, and I feel sorry for the one who writes site modeling code. It is getting better with each refinement.

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