I work for construction company as an estimator. Just to be clear, my background is in GIS, Urban Planning and Surveying. I'm quite versed in AutoCAD design and also use it daily for calculating quantity takeoffs for proposed construction projects.
Here's my question. I've been testing Civil 3D as a quick method for calculating cut and fill quantities. I've done some reading and I think I've figured out a simple method of doing this. What I would like to know is if I'm doing this properly.
Below are the steps I've taken to produce my numbers:
1. Existing and proposed elevation marks in the AutoCAD drawing are assigned points with correct z elevations.
note* the existing and proposed elevations cover almost the exact same surface areas. To be clear, if a polyline was connected around the boundary points of each layer, they would almost match up.
2. All points are brought into Civil 3D
3. Existing points are converted into Civil 3D cogo points with the description "existing"
4. Same process as step 3 used for the proposed points with the description "proposed"
5. Existing and proposed cogo points are assigned to separate point groups with relative names
6. Two TIN surfaces are created with surface style "Contours 1m and 5m (design)"
note* I'm not sure what the difference between the (design) and (background) options are
7. Both existing and proposed point groups are assigned to each relative surface.
8. A TIN volume surface is created using surface style "Contours 1m and 5m (design)" and the "existing" TIN surface is assigned to the base surface, with the "proposed" TIN surface assigned to the comparison surface.
note* Cut and Fill factor are left at 1.000, as I'm unsure how these values effect the TIN volume surface.
Basically that's it. I'm getting some nice cut and fill numbers when I check the properties of the volume surface and they do seem to be accurate, but I would like to be 100% sure that I’m getting accurate information
To reiterate, I am very new to Civil 3D, and any input on my method would be greatly appreciated.
p.s. I've attached the file "Cut fill test.dwg" if you would like to see what was done.
Since you've created a comparison surface - 'Cut Fill'. You can also create color schemes to verify where the cut and fill areas respectively are.
At a glance your drawing looks correct.
you can also use the surface volume feature under the sufaces pulldown, utilities. I typically just use this feature unless i need to display a color scheme for cut and fill areas. You also have to consider in a compression factor. when they bring in dirt for roads or lot grading they are going to pack it down. In the surface volume feature i typically use a 1.15 fill compaction factor. anyways hopes this helps.
Senior Design Tech
Always remebering that the cut and fill factors (also called bulkage factor, swell factors,compaction factor) can vary with material type and compaction method etc so use with caution.
The other thing to consider is that the spot levels accurately define the surface and that breaklines are not required to enhance the triangulation
But just as far as using C3d 2011 i use C3D as a survey & design "mostly" and next a Vols Qc for complex highways
Without a sample of your project I have found that you may be up the creek.
No 1 civil 3 D is complex with no such thing as a casual user, autocad background more or less of small benefit
Survey robots 1/10 complexity
Gps 1/10 complexity
C3D 9/10 complexity - it is not a estimating tool i am sad to say unless you use say C3D all day long
But i would say that i Like C3D for it is fare better that LDT (user simple) since 1999 however the complecity has
gone way of the scale
PS i have my own small survey company
Any comment on your procedures would be difficult at best
i loloked at the DWG and it may be in the long run to farm the work out for like i said C3d is complex and i
would be better to look at a simplier program to hunt down stock pile volumes or excavation volumes.
For a most projects now are made up of assembly of endless drawings and to piece it all together is a chore
for sooner or later you will require design C3D dwgs
Your basic premise is right. Create an EG surface from your topo points, and a FG surface for your design points and wither use the volume tool or what you're doing.
The two surfaces do not need to agree in size as the smaller surface will be used.
The same thing can be done in ArcGIS but takes longer and you need to use extensions. C3D is much faster. I do the same as you on a daily basis to estimate volumes. Ignore the suggestion to outsource.
Design and background contour styles are simply different so yo ucan visually tell the difference between youe EG and FG surfaces.
The factors are based on compaction and expansion depending on what you are removing in cut and fil; different materials compact and expand at different rates. For a high level number, leave them at 1.
When it comes to farming out this work, it just makes no sense. We have some great Trimble based GPS hardware that we use for site layout, and C3D would complement our surveying hardware as much as our estimating numbers.
As for the rest of the comments, I appreciate all the input. This sounds like the best method to produce the data I’m looking for.
As for bulking and compaction factors, they are always in the back of my head, but I do appreciate the advice.
I also agree ESRI products can produce much of the data I’m looking for, but GIS software (as much as I love it) is somewhat unnecessary for a construction company. On a side note, I have heard good things about Manifold though (cost vs. capability).
Again, thank you all. It is much appreciated.