Most typical sections would be constructed perpendicular to the base line. If 2:1 is exceeded in that direction, the onus is on the designer to corect the typical section to provided for the inevitable skewed slope exceeding maximum.
I am on the CADvisers side in this. A 2:1 slope on a typical highway project is measured perpendicular to the direction of the roadway. Send a knowledgeable surveyor to set slope stakes and he sets them based on perpendicular distance from his hinge point on the edge of the slope.
The OP won't post his drawing with the example, but I suspect CADverse is correct, he isn't building his 2:1 slope correclty, but adamantly believes that he is. I'm done looking at this until he responds with his file. Still, there probably is room for improvement with contour construction, but I can't see how such a miniscule deviation would matter in the case of land development. Most state and local regulations I believe allow some deviation in construction. If something needs to be that precise I recommend the OP to create the points himself and send those to survey; good luck constructing it that accurately. I've never had an asbuilt completed that didn't show at least a tenth or two in deviation.
Right it's simply a Convention matter... Like Ms. Mercier said long ago, Gradings (and Corridors) construct their Daylight projections perpendicular from the Feature and the contour output is a function of that Convention.
So, it's not "wrong" per se. It's correct for its Convention.
Another thing to think about, why is the requirement 2:1? Well, it's because 2 is a nice easy number to remember. Why not 1.94:1? Why not 2.37:1? Did someone actually go out and calculate that in this particular situation, the optimal slope for this design, based on good engineering judgement, life and safety considerations, cost of the project, ease of constructability, is exactly 2:1?
Instead it probably went something like this, "I've used 2:1 in the past in areas like this and it seems to work pretty well, we should probably use 2:1 again in this area."
So, ask yourself this, why is slightly steeper then 2:1 in this area a bad thing and the answer is most likely, "because the city/state/county/<insert other reviewing agency> said we can't go steeper than 2:1".
I had the same type of thing come up when I was doing design for some utilties. The design criteria said that the sanitary sewer and the waterline had to be a minimum 10' apart. In my design, for about 2', they were only 9.5' apart.
Who came up with this magic number of 10'? Again, it's a nice easy number to remember and is close to (error on the side of caution) what the actual minimum distance between the two utilities actually should be.
And, yes, I ended up redesigning the utilities.
Better yet add some coordinates to those contours to get extra close
"All Contours are lies"; all it take is one look to see - flip a face for example
2:1 max slope is definitely per Code (IBC, IRC, HUD) that US jurisdictions follow.
In that regard, I acknowledge the OP's original concern of the use of C3D projection grading tools by his staff, if they do not understand the projection grading convention.
Regarding that, I would not want to give the other side's attorney any opportunity to demonstrate the design is below
code in deposition.
Wow ! So now we need a projection grading that finds the first contour then turns to be perpendicular to it?
Add more coordinates!
The 2010 maintenance code fro ADA forces a maximum 2% cross slope ... Actually 1:48 which theoretically is 2.08%, but reviewers are stuck on 2%. So now when I grade an ADA accessible route that will obviously have a longitudinal slope less than 5% - 2% of that will invariable lead that some point being a tad over 2%. What's the answer? 1.9%
sometimes you need to adjust for code values. If ambient conditions are going to create a daylight slope to exceed 2:1 then my suggestion is to use a value slightly flatter to insure maximum is not exceeded.
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