Road Design Project Help

[Anonymous]

Hi, I am a student working on a project and wanted to see if I had the right idea as to my workflow. Hopefully you all will be able to save me several hours of time. 

We are trying to determine if the as-built conditions match the design of a simple gravel road subdivision facing serious erosion issues. We have the subdivision surveyed and have a surface, alignment, and corridor developed for the existing conditions. We have it set up displaying the existing elevation profiles cross sections, but we are running into issues comparing it to the design. This part seems to be going well. 

So far, I have the a surface developed using the topo sheets from the design documents. This was from adding elevation data to the 2D polylines and creating it that way. Here is where we are running into issues. The surface is at a different scale than the existing conditions, and when trying to use the align function using the known points it will only align to a single point rather than the three we're selecting. It also not scaling. 

My goal was to overlay the two surfaces and corridors onto each other, and have the cross sections overlay onto each other. I'm hoping somewhere in there I can pull out the total volume required. 

Am I going in the right direction? I have the design cross sections, would it be easier to compare the existing conditions to these directly vs. the surface created by topo? Our ultimate goal is to tell the client which sections need fill. Any assistance would be greatly appreciated. Thanks 

[chriscowgill7373]

Typically you should not have to scale a surface, unless for some reason different datums were utilized.  If that is the case, the information should be translated to so both sets of data are using the same datum. Then they would come in at the same location, and no manual aligning or scaling would be  required. Unfortunanetly I dont know much about the c3d data translation tools, our surveyors handle that part of the projects.

[ChrisRS · Accepted solution]

You have an as-built surface based in your survey.

I think that you are on the right track. 

How did you create the plan based design surface? What do you mean by a different scale? 

There should be enough data on the plans to allow you to draft the centerline, etc. and recreate the original plan. If you had the plans somehow scanned or converted, and they are to the wrong scale, you should be able scale and rotate. Align does this in one step, but i fear that it will also scale the elevations. Unless you use a sophisticated transformation program, you will need to check and correct the transformed elevations.

After you have a good design surface use the 2 surfaces to create a Volume surface, which will give you cut and fill volumes.

If there are areas you do not want to include in the volume calculations, you can apply hide boundaries to one of the surfaces. (Volume is only calculated for the area where the displayed portion of the surfaces overlap.

You could also create an alignment, a profile alignment and the 2 surfaces, add sample lines and create cross section to se where the fill is needed.

Good Luck,

Chris Stevens

[ricksr · Accepted solution]

I recently had to move, rotate, and scale a surface.  Moving and rotating is pretty easy (see this link:

https://knowledge.autodesk.com/support/autocad-civil-3d/learn-explore/caas/CloudHelp/cloudhelp/2017/...

but scaling a surface is more complex, because when you scale a surface, you are also scaling the z direction (elevation), which you usually do not want to do.  I found there are two ways to scale a surface.  The first is to make a wblock of the surface with an insertion point of 0,0,0.  Then insert the block at 0,0,0, turn off the "Scale uniformally" switch, and for Z enter 1, then for X and Y enter the needed scale (make sure X and Y are the same value).

It's important to note that when you  make a block of a surface and insert it, it brings all the data that was used to build that surface with it (breaklines, contours, etc.).  So you may want to insert this block of the surface into a new drawing as explained above.  This new file would then be the home for this surface and you would make a data shortcut of it and reference it into the original drawing to do your comparisons and volume calcs.

The second method of scaling a surface is found in this link:

https://knowledge.autodesk.com/support/autocad-civil-3d/getting-started/caas/screencast/Main/Details...

[ChrisRS]

@ricksr, you are absolutely correct. Scale is wrong. I meant Move and rotate.

to be more clear: If you are recreating you design information form the plans you should not need to scale.

[Anonymous]

Thank you all for responding. This was immensely helpful.

From what I gathered attempting to scale the surface directly will be a nightmare. My new plan is to simply scale the plans in just XY using my datums on the survey surface then create the design surface then.  There were several questions about what exactly i was scaling, I simply scanned the plans and used an online converter to convert from PDF to DWG. I'm not sure what the scale came in as, and I do not believe the scale on the drawing was preserved. Im working on a 1:1 scale with the survey data, so I am trying to get this drawing scaled to the same as the survey. If this doesn't work I may be back. Thanks again.