earthwork calculations

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earthwork calculations

Postby steve » Wed Apr 06, 2005 10:55 am

we were asked to do a earthwork volume calculation based off of plans prepared by others. we had only paper drawings which we scanned into a tiff image & brought into a new drawing file. before doing anything with the tiff image, we scaled up the image by the correct scale factor to bring to the plans to actual foot dimensions. there is 192 lots on 7 sheets of plans. we did this for each plan.

next, working on individual sheets, we traced lot lines & other reference lines. we then traced the proposed contours using 3d polylines and setting the correct elevations. we also did the same for the existing contours.
this was done for each sheet.

now, we would like to connect each sheet to create one large plan of the entire site. i know this can be done & how to do it. however, we cannot edit the 3d polylines to connect to the cooresponding polyline on the adjoing sheet.

i have preformed plenty of volume calculations using points to create the surfaces. i have not used polylines in this fashion to create a surface. i think based on what i have seen, that this can be done.

my questions: is it necessary to connect said polylines? is this necessary to extract the surfaces from the polylines? am i doing this right? has any one else tried this and have any suggestions?

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Postby Glen Cameron » Thu Apr 07, 2005 4:12 am

You can use any 3D data to create a surface. So 3D polylines can be used to Extract to Surface instead of point data. They do not need to be joined together, as long as they are correct and represent the surface, they can be used as is.

Glen W. Cameron, C.E.T.
City of North Bay, Ontario
Glen Cameron
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Postby steve » Thu Apr 07, 2005 6:44 am

thanks glen. will let you know how things work.
Posts: 16
Joined: Mon Nov 18, 2002 9:03 am
Location: haddon heights, new jersey

contour volumes

Postby Vincent Popish » Thu Apr 07, 2005 12:01 pm

If you have a valley or a ridge on the contours and just use the contour lines to generate the surface, it will give you the wrong volume answer. The reason is that the program will triangulate accross the ridge or valley and ignore the valley or ridge when it is ib a concave shape. One needs to add the rige or valley line in the form of a 3d polyline so that the tin will triangulate to the ridge line and prevent it from triangulating accross the concave contour. I hope this explains it enough so you get the problem with just using contours.
Vince Popish
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