Cut/Fill Summary surface volume differs from Elevations Table surface volume

[Anonymous]

I think that the cut/fill summary volumes should equal the volumes in the surface legend table. They do not. Is this just a bug or is there something I'm missing? 

Why doesn't the total of cut from the surface legend table (5313.00 + 2786.24 = 8099.24 cy) equal the total cut from the cut and fill summary (8098.19 cy)? It seems to me they should be the same since they're measuring the same thing.

Same for fill.

[Anonymous]

Here is another example:

Which is correct? Is the cut volume 8099.23 or 8098.19? Is the fill volume 8381.71 or 8382.97? Which should not be used, volumes calculated by surface legend table or volumes calculated by volumes dashboard? 

[KirkNoonan]

Wow, you're worried about 10ths of cubic yards? Dirt must be expensive where you are 

The cut-fill analysis generates a volume surface and which is the difference between two surfaces. I think the elevation surface report is more like the prismoidal method using the areas at each elevation step.. I always do both and sometimes use the section analysis and/or stage storage tool and then apply some common sense to get a value.

There is a lot of information in the help files.

http://help.autodesk.com/view/CIV3D/2015/ENU/?guid=GUID-ECD225E2-C049-4781-9864-50CB6A5E2494

[Anonymous]

No, it's about credibility. If the numbers don't agree then the contractor is not going to believe them.

I actually found on another drawing that the quantities are exactly the same. There is something drawing specific creating the difference.

[Anonymous]

It's also off by about a whole cubic yard, not 1/10 of a yard. If the difference were close enough to show the same number just by dropping decimals, I would.

[KirkNoonan]

Based on my experience, a 1 CY discrepancy in an 8,000+ CY estimate is pretty good. I would challenge any contractor to demonstrate that he has an exact enough calculation of his fluff/compaction factor that your being off by 1/8000th is going to make a difference in his cost.

It is easy to spend an inordinate amount of time splitting hairs with this software, but the returns dwindle quickly.

One factor might be tin lines at the edge of your surface that stretch beyond the limits of the surface and create false areas. Do you have the same boundaries applied for each of your volume calculation methods?

[Anonymous]

Yes, same boundaries. The discrepancy is an error in the drawing. I'm getting un-handled exception errors now. I am recreating the surface and hopefully it will work now.

Bro, you are preaching to the choir. If I had contact with the client and/or contractor I would explain everything, however I do not. The quantity is off by an insignificant amount, yes, but the fact that the numbers don't jive, it doesn't matter if it is off by 1/100000, or 1000000, the integrity of the numbers is compromised. How do you know you are only off by 1 cy? How do you know both numbers aren't off by 1000? 

[Anonymous]

ok, one yard or 1,000 yards.  you are a PE and you ask how to know if it is off?

do the math by hand - have the computer set up a grid and give elevation differences between the two surfaces and then crunch the numbers with average end areas and check it.  the difference will not be much - should be less than 50 cubic yards, if you are good at it.   Used this method too many times for a PE who just HAD to see the numbers.

good luck and have fun.

[Anonymous]

There are a handful of different methods of calculating earthwork and they all will come up with a different total.   That is why you have a specification telling the contractor how you have calculated the earthwork and then he has no argument unless his measurements and the same method of calculation comes up with a different quantity.  But It's great having the dashboard method to get a check on our other earthwork quanities.  

[Anonymous]

I understand what you're saying but the two methods I pictured above will result in the same total when functioning correctly. I should have said above that this is a dead thread, the error is due to drawing corruption, not an error in the software.

[Anonymous]

Yeah, the work was done already. I just wanted to understand why in this one particular drawing the calculations were coming out different than all the others. It was due to a corrupt surface.

[gustavo_bergoya1]

Hi,

It's happening to me and I think it's a mistake in the surface analysis table

[gustavo_bergoya1]

I did not have this error before

[Anonymous]

hello,

the real question is: what is the difference between the two values?  and what percent of the total is that?

if you are looking at 10-20 cy difference and the total cut/fill is 2,000 cy, that is 1.0%.

what is the cost of 20 cy?  verse the time to change 1.0% difference?

when I used LDD, I would run cut/fill with the three options for calculations and then average the numbers for my totals.  Engineers would cry murder and I would laugh and ask them to do their own calculations.  

if the difference is less than 10%, I would just run with the numbers and go.

good luck,

nonbeard13 

[ChrisBlind]

Hi,

Here's a weird one for you all. I have two surfaces 250mm apart (topsoil strip depth) and the elevations table reports a total of the volumes between the ranges of 195.6m2 no matter what the interval selected and the volume in the statistics tab of the surface properties reports 933.62m2 There is clearly an error but I have recreated this numerous times with the same data set and the same discrepancy occurs... The extent is 2,962m2 with a stockpile in the middle so I know the correct answer should be 933.62 but how do I make the table match....

Cheers

Chris

[gustavo_bergoya1]

Hi  ChrisBlind

I have noticed that this happens only when the two surfaces do not connect, that is, a daylight is necessary that you join them so that the volume in that table coincides.

Regards

[j_schroeder1]

been trying to present this diminishing returns concept to my colleagues for years now. it's ironic that the folks that seem to get most hung up on it are the old-schoolers who had careers pre-autocad. 

[akeicher]

I know this is an old thread, but I am seeing this discrepancy for the first time. I do a lot of volume work, and in the past the Volumes Dashboard and the volumes listed in the Elevations Table always add up to the same total (give or a take a CY due to decimal display/rounding). Today however I have a volume surface comparing an existing surface and a design surface, and the volume dashboard calculations differ by as much as 22 CY compared to the Elevations Table. I agree that this is insignificant in the grand scheme of things considering I'm dealing with ~700k CY, however it disturbs me that these volumes differ at all, considering I have never seen this error before when doing these analyses. 

Also note I have another volume surface comparing the same two surfaces, only using a different boundary to "clip" and analyze an area of concern. In this case both the V.D. and E.T. values match exactly!

As another has suggested, there is an area of the design surface that is "missing", essentially producing a small hole in the surface. However, I have previously done a volume comparison between this same design surface and a previous existing surface and did not have the discrepancy between the V.D. and E.T. values.

Does anyone know what could be causing this?

Thank you,

[tcorey]

" it's ironic that the folks that seem to get most hung up on it are the old-schoolers who had careers pre-autocad. "

They pine for the days of hunching over a drafting table, using a planimeter to buggy cross sections, which they drafted by hand.

[fcernst]

It looks like the table is probably giving the volume of the outer cone shape of the proposed surface, not the volume of Cut.