Finished grades from contours

There are several ways to go but the first question is do you have the CAD drawing??ÿ If there are no profiles I doubt they were generated.?ÿ You will have to generate everything you need from the CAD drawing.?ÿ That is what I end up doing most of the time with today's plans.

Posted by: Scotland

There are several ways to go but the first question is do you have the CAD drawing??ÿ If there are no profiles I doubt they were generated.?ÿ You will have to generate everything you need from the CAD drawing.?ÿ That is what I end up doing most of the time with today's plans.

Yes, I do have the CAD file.

This is the way civil eng is going. Assuming the field you have is c3d, you can pull everything from it, the surface will give you elevations anywhere you need. There should be a profile down the road you can export anything XML and stake from.

I dislike this from a liability standpoint, and I hope you are getting at least 20% more fee, but I saw this happening in private eng practice. The reason is we would spend days drafting detailed curb sheets, x sections et al, and we wouldn't get the staking because we weren't the cheap scrubs, then the scrub would call and demand c3d files to save themselves entering data by hand. If you resist the scrub gets contractor wound up, who gets the owner/you client mad at you. So we stopped wasting drafting time, even on jobs we would be staking because us surveyors would be able to pull c3d data. Of course at our liability, annoyance and worst of all without any budget giving us time.

I prefer contours and spot elevations because the information is given, not needing to be calculated. I will ask for additional spot elevations if the aren't enough in?ÿ a particular area.

That is common today on low budget jobs, limited engineering. Most if today's contract plans are for planning board approval only. An accurate 3d surface model can be created from contours and spot grades, using correct techniques and software such as Carlson TakeOff or InRoads. You will need to create accurate break lines for crowns, edges, ditches, etc.?ÿ

?ÿ

Reverse engineering contours to create a surface will not give you accurate results. Be careful doing it that way

For small site projects reverse engineering from contours and spot grades is the only way to create a surface. Building appropriate break lines, checking for positive drainage, create your own profile, check for flat areas and verify slopes, this is common procedure for an accurate model. If there is not enough grades on the plan or you have questionable areas, then file an RFI. In the end display contours of your FG surface at 1/2 the interval shown on plan and look for spikes and none conforming contours. Never create a road surface from contours only, you must create the breaklines. Check and comply with the typical road section.

I have been asked by graders on several occasions about previous sites they had graded (not my models) regarding why their blade would bounce every once in while. I told them the fellow who built the model didn't use or create any breaklines. How can you create machine control models for a living and not use breaklines??ÿ

Posted by: Tim V. PLS

I prefer contours and spot elevations because the information is given, not needing to be calculated. I will ask for additional spot elevations if the aren't enough in?ÿ a particular area.

oof thats dangerous. If you have profiles you should never build off the contours or spot elevations alone. Build off of Profiles and spec sheets first, check against the contours and spot grades and then see if they match. If they dont - which is almost always the case from what I found - you either need to go back to the engineer or see which way makes the most sense and adjust it.

Well, the engineer is only going to provide a few more spot elevations. I told the contractor that there are a few areas that I'm not comfortable with. He said he'll make it work in those areas (it's only a few small areas so far). I guess I'm going to have to note those areas carefully.

Most of my construction layout experience has been with my previous employer (Engineering and surveying) and apparently they did a pretty good job with providing surveyors what they need.

?ÿ

Gregg

Like above, ?ÿuse typical section for the roadway. ?ÿCreate break lines from the contours along your side slopes. ?ÿI would not ?ÿuse the contour for your final design after ?ÿbuild your roadway and create break line. All you want is breaklines (grade breaks) for your design. ?ÿThose contours will just give you a bumpy design. ?ÿ Check for drainage issues and generate your own contour for a comparison. Best of luck

@frankg

Thanks for the tips. That job has been over for a long time now. My bank account is a bit leaner without the construction money but I'm sleeping much better. I learned a lot on that one though.

Gregg