Hi All,
I have come across a fairly major discrepancy between volumes calculated by me, using Exact - tin to tin, and those calculated by the contractor from the same tins but using End Area - sting tin to tin.
THe contractor has diveded the project into sections to get his volumes. When I used the same sections, using polygons, with Exact - tin to tin, I got the same volumes as I had previously recieved using the same method one the job as a whole.
The job is an intersection upgrade of a 4 leg round about to a 4 leg intersection controlled by lights and includes approached of between 300m and 500m.
I have been able to duplicate both sets of volume results.
Does anyone know why this would be happening?
Phill
Differance in Volume Calculation Methods.
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Phillip Harris
- Posts: 16
- Joined: Fri Oct 28, 2005 2:03 pm
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Peter Taynton
- Posts: 1459
- Joined: Mon Oct 17, 2005 8:07 am
Phil
What was the difference you got?
The end area method does rely on the interval specified and may not show up discrepencies in the existing and or design between the sections.
All I can suggest is to run the sections at a closer interval.
I would have to have some data to really check it out much further.
Peter
What was the difference you got?
The end area method does rely on the interval specified and may not show up discrepencies in the existing and or design between the sections.
All I can suggest is to run the sections at a closer interval.
I would have to have some data to really check it out much further.
Peter
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Phillip Harris
- Posts: 16
- Joined: Fri Oct 28, 2005 2:03 pm
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Peter Taynton
- Posts: 1459
- Joined: Mon Oct 17, 2005 8:07 am
Yeah....well that's not within 5% is it 
There must be some reason...will check it out
Peter
qld12d@bigpond.com
There must be some reason...will check it out
Peter
qld12d@bigpond.com
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Peter Taynton
- Posts: 1459
- Joined: Mon Oct 17, 2005 8:07 am
Phillip
After looking at you data.....I can say that 12d does do the volumes correctly....it is just a few things need to be noted when using the End Area method
In your case the triangulations formed a four way skewed intersection:
The end area option has a chainage range along a selected Alignment...but there is no search distance left or right.....it uses an infinite distance.
So the sections used would in some places cross over two or more legs of the intersection.......resulting in volumes from two areas.
If you use the same polygons as you did in the exact method....then the poly limits the extents of the cross sections used.
A good check is to fill out the entries for "Original tin sections " and or "New tin sections".....then you can add them to the view to see exactly what sections are being used to extract the volumes.
Peter
After looking at you data.....I can say that 12d does do the volumes correctly....it is just a few things need to be noted when using the End Area method
In your case the triangulations formed a four way skewed intersection:
The end area option has a chainage range along a selected Alignment...but there is no search distance left or right.....it uses an infinite distance.
So the sections used would in some places cross over two or more legs of the intersection.......resulting in volumes from two areas.
If you use the same polygons as you did in the exact method....then the poly limits the extents of the cross sections used.
A good check is to fill out the entries for "Original tin sections " and or "New tin sections".....then you can add them to the view to see exactly what sections are being used to extract the volumes.
Peter