Profile grade label precision

[Anonymous]

Because of rounding or not rounding; My profile grade label is slightly different than if you calculated what you see by hand.

Example:

PT A: Sta 20+78.22  Elev 968.57

PT B: Sta 20+99.79  Elev 968.95

Civil Grade Label Between = 1.74%

Calculated grade by hand = 1.71% 

In the Civil Drawing Ambient Settings: I have set Distance, Elevation, Grade, Grade/Slope & Station Precision to 2 and rounding to truncated.

In the profile labels I set the grade (component: tangent grade) precision to 2 and rounding to truncated.

In the profile labels I set the Grade break (component: pvi Sta & Elev) precision to 2 and rounding to truncated.

I know this is pretty technical, but some one is reviewing this by hand and the grades need to match paper hand calcs.

Thanks

[civilman1957]

I don't know about anyone else, but I get 1.761706 when I do it by hand. not sure where 1.71 comes from...

[troma]

I get 1.76%
Are there any horizontal or vertical curves?

[Anonymous]

No curves.
They area straight areas between vertical curves on horiz tangents.

[Anonymous]

Yes your right 1.76% by hand.

I think was getting confused with changed things to truncated.

[Anonymous]

So its 1.74% (civil)
vs 1.76% (by hand)

[civilman1957]

Well...not to sound flip, but if someone is going to lose it over .0002%, they need to have their workload increased...

[troma]

Civil is calculating the grades from the actual numbers.
Hand calc is only looking at the rounded numbers.

If your reviewer wants them to match, you need to display more precision on your numbers.

[cwr-pae]

Create an expression to calculate with the same precision/rounding you would get if calculating by hand.

This is one I use:

ROUND((ROUND({Tangent Elevation Change}*100)/100)/(ROUND({Tangent Horizontal Length}*100)/100)*10000)/10000

[troma]

Example:
PT A: Sta 20+78.2170000 Elev 968.5730000
PT B: Sta 20+99.7910000 Elev 968.9480000

Actual grade between = 1.7382033%
Civil Grade Label Between = 1.74%

But if you round the station and elevation numbers first, then you will hand calculate it to be 1.76%

[Anonymous]

Tell me about it. My rule of thumb is, Can the contractor build it, is it practical to build, does it comply with code and will anyone's safety be compromised (will we be liable for a lawsuit).

Thanks

[Jeff_M]

I went to battle with a plan checker here over this kind of thing, and won. My argument went like so:

I use the slope to determine the elevations, not the elevations to determine the slope. Example:

20+99.79 - 20+78.22 = 21.57

21.57 * 0.0174 = 0.3753 or 0.38

968.57 + 0.38 = 968.95 which is the identical number shown on the plan

After taking 3 similar examples directly from the plans they red marked, they finally caved in and agreed, especially since they specifically said the elevations must be to 100th's only.

[cwr-pae]

I like Jeff's approach, I just haven't been able to win the battle yet.

Kudos for the win 😉

[Anonymous]

I ended up writing these expressions. I broke them down to simpler ones and combined them in the end. This way I could check the individual expressions as I went. For what ever reason the one you posted didn't work in all my grades but it led me to the ones below. thanks.

Change in STA:

TRUNC(({Tangent End Station}-{Tangent Start Station})*100)/100

Change in Elev:

TRUNC(({Tangent End Elevation}-{Tangent Start Elevation})*100)/100

Percent Calc by Hand:

{Change in Elev}/{Change in STA}

[Anonymous]

ok, we can design to an insane number of decimal places . . . .

ground survey is plus/minus a tenth ( 0.10 ) yes, i know the elevations are to the hundredth 0.01-foot

design is to a tenth or better - depending on rounding

construction is +/- 0.10 foot usually - unless you are building a rocket sled track (not many of those any more . . . .)

I am with Jeff.  CONGRADS to you sir!!!

[troma]

I'm with Jeff's method. Civil's calculation is more accurate than the hand calcs. Why are you adjusting your labels to display incorrect information?
If I had to fight someone over this, I'd like to adjust my elevation and station labels to at least 5 decimals and plot them the drawings. I'd tell them "this is the special drawing set, just for you to check". Then on the regular drawings, put the decimal display back down again. This makes it obvious what's actually going on, and shows that the slope is calculated correctly.

[Anonymous]

I totally agree. Some people just want it as if you did your design work on paper.