AutoCAD Land Desktop

AutoCAD Land Desktop

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ktyll
Posts: 58
Registered: ‎12-11-2003
Message 1 of 4 (65 Views)

volume calcs within boundaries

65 Views, 3 Replies
10-20-2003 10:50 PM
My company is on the verge of buying LDT 2004 and I have a question regarding capabilities. I am looking at a project that I need to get volumes between two different surfaces in many different areas with separate boundaries. Is there a way to set a boundary so that you only calculate the volumes within a specific area?

Thanks.

K. Tyll
Roux Associates
*bouza, Joe
Message 2 of 4 (65 Views)

Re: volume calcs within boundaries

10-20-2003 11:21 PM in reply to: ktyll
Hi, Yes. Define all your specific boundaries as LDD
"Parcels" then you can get total site & parcel volumes.

 

Joe


style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
My
company is on the verge of buying LDT 2004 and I have a question regarding
capabilities. I am looking at a project that I need to get volumes between two
different surfaces in many different areas with separate boundaries. Is there
a way to set a boundary so that you only calculate the volumes within a
specific area?

Thanks.

K. Tyll
Roux Associates

*Boys, Doug
Message 3 of 4 (65 Views)

Re:

10-21-2003 07:47 PM in reply to: ktyll
Be careful. Sometimes using Parcels to define volume calculation boundaries
runs VERY SLOW.

 

I think it would generally be much faster to use each subarea closed
polyline boundary as the Outer boundary for one of the surfaces, re-build the
surface then do volume calcs for the whole Stratum. Then use the next subarea as
the Outer boundary and repeat.

 

Doug Boys

Cardno MBK Brisbane

 
*Cannon, Steve
Message 4 of 4 (65 Views)

Re:

10-22-2003 01:13 AM in reply to: ktyll
Doug,

FWIW, Just an added thought...

Programmatically, one of the biggest stumbling blocks to accurate volumes is
the vertical boundary clipping planes at the limits of computation. While
composite volumes seem to do a very good job of dissecting sub-triangles of
both surfaces at the linear boundary of the controlling surface, Composite
Parcel sub-volumes are not as accurate. I can demonstrate this by taking a
site, dividing it into parcels, and summing the individual parcel volumes -
they will not exactly match the composite calculation done over the entire
site. I believe this is do to the fact that the triangles are subdivided at
the time the composite surface is created - in other words, the composite
surface contains sub-triangles which were cut accurately by the outer
boundary clipping plane. However, at the time the composite surface is
created - LDT is not aware of parcel boundaries and therefore can not
dissect the sub-triangles along parcel boundaries. Subsequent parcel
boundary computation is based upon that previously computed composite
surface and therefore needs to 'round' values at the parcel boundary. That
said and done, for most civil type work the error is going to be
insignificant (much less than 1%).

Note also, that as Marv has pointed out several times, you can have LDT
curved parcel boundaries, but parcel sub-volumes ignore parcel legs that are
curved and computes the boundary along the long chord - which could add up
to significant error in some cases.

sc

Doug Boys wrote in message
news:F0ECFE8B82184332BE5396F250B4C2BA@in.WebX.maYIadrTaRb...
> Be careful. Sometimes using Parcels to define volume calculation
boundaries runs VERY SLOW.
>
> I think it would generally be much faster to use each subarea closed
polyline boundary as the Outer boundary for one of the surfaces, re-build
the surface then do volume calcs for the whole Stratum. Then use the next
subarea as the Outer boundary and repeat.
>
> Doug Boys
> Cardno MBK Brisbane
>
>
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