Thread: Calculating pipe slopes

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Calculating pipe slopes

When Civil 3D calcs pipe slopes it uses the inverts of the pipe and the 2D distance between endpoints of the pipe. However when we label the pipe distance we like to "Round Normal" when showing the length of the pipe. The problem we're having is when you then do the math on the rounded distance and inverts of the pipe, the slope is wildly different from Civil 3D's slope. The question is can you tell Civil 3D to round the pipe distance using "Round Normal" first and then calc the slope of the pipe. The only reason this can be, and is and issue is we have an in-house review team that calcs out the slopes with a calculator to check our work and they're constently coming up with different slopes from what the label shows. I'd like for Civil 3D to be able to see the distance of the pipe as 55.345 linear feet but still use 55 linear feet for the slope calc. Can this be done? Is there anywhere you can tell C3D to round the raw numbers?

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Re: Calculating pipe slopes

I don't know how to make C3D calculate the slopes less accurately but you could display them with less accuracy. Just change the precision of the slope lables to 0.0. This still may not work for you but it's worth a try. The other option is to show your pipe lengths to a precision of 2 (0.00). That is what we do.

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Re: Calculating pipe slopes

A precision of 2 is just not necessary in the field, especially since the pipes are never as long as the 2D distance between the centers of the boxes due to the size of the boxes themselves. It would be like giving construction information to the knats...... butt knowing full well the numbers given are 2 to 5 feet off anyway. That's why we round to the nearest foot, but in doing so, the QC people think we don't know how to work our calculators over here. Oh well. I guess I'll just clue them in to what's going on with the program.

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Re: Calculating pipe slopes

You can make an expression to calculate the slope however you want. What you want is something like ([round elevation 1]-[round elevation 2])/(round distance).

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Re: Calculating pipe slopes

Originally Posted by Brian Hailey
You can make an expression to calculate the slope however you want. What you want is something like ([round elevation 1]-[round elevation 2])/(round distance).
Where do you add the expression though? Is it simply a label style or is there something that will change the way C3D calcs it? Labeling it would work good but to list the pipe properties and get the same result would be ideal.

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Re: Calculating pipe slopes

In the settings tab at the same place your label styles are located, you'll see at the bottom of the list, expressions. Simply create a new expression and then that expression will be available in the labels properties.

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