topic Re: problem with Length in Civil 3D Forum

problem with Length

Anonymous — Fri, 04 Mar 2016 17:14:50 GMT

Hello I have a problem to find out the correct distance. Drawn a horizontal line length is 1000.55 and profiling its length 1039.59
Any of them true length of the line?

and how to know the 3D Length of profile in civil?

THANK YOU !!

Re: problem with Length

Joe-Bouza — Fri, 04 Mar 2016 19:01:01 GMT

The profile is reporting the horizontal distance along and alignment. If you have to have the 3d length you can set the profile type to static and list its length or explode a copy and list

Re: problem with Length

Jeff_M — Fri, 04 Mar 2016 19:42:56 GMT

Joe's method requires the profileview vertical scale to equal the horizontal scale....

Re: problem with Length

Joe-Bouza — Fri, 04 Mar 2016 20:21:41 GMT

Oops!

Good catch

Re: problem with Length

Anonymous — Fri, 04 Mar 2016 21:06:15 GMT

I Create feature line from alignment and it show me the 3D length 1129.184m , and the 2D length 1001.57m , It's puzzeld me , I am very confused

that is the file I want the real length .

Re: problem with Length

Pointdump — Sat, 05 Mar 2016 21:10:13 GMT

Ahmad,

Welcome to the Forum. Properties shows the 3D length is indeed 1129.184m.

Dave

Re: problem with Length

fcernst — Sun, 06 Mar 2016 14:43:30 GMT

It's puzzeld me , I am very confused

"3D" is the Length.

"2D" length in Civil 3D is simply the length projected on to the XY plane (Length*cos(theta)). It's a civil engineering convention.

Re: problem with Length

BrianHailey — Sun, 06 Mar 2016 15:57:01 GMT

I think the reason why we do this is because when a long linear feature if fairly level, the horizontal (2D) length is very close the to the actual (3D) length. For example, if a pipe is put in the ground at a slope of 5% and has a horizontal length of 100m, the actual 3D length is 500.62m. If you are trying to estimate the length of a pipe to that accuracy, good luck.

The slope of the pipe required to get an error of 1% would need to be just over 14%. At that point, it would probably be prudent to investigate the 3D length vs. the 2D length.

Re: problem with Length

Pointdump — Sun, 06 Mar 2016 17:02:47 GMT

Brian,

"... if a pipe is put in the ground at a slope of 5% and has a horizontal length of 100m, the actual 3D length is 500.62m."

500.62 sounds kinda high. Would that be for a slope of 5% off of Vertical?

Dave

Re: problem with Length

Anonymous — Sun, 06 Mar 2016 17:17:49 GMT

thank you very much
I am glad to be here with kind people like you.

Re: problem with Length

Anonymous — Sun, 06 Mar 2016 17:26:21 GMT

but How i can Prove the 3D length is : 1129.184m not the 2D length 1001.57m to my consultant ?

Re: problem with Length

Jeff_M — Sun, 06 Mar 2016 18:21:57 GMT

Show the featureline in both plan and profile. the 2d length is what you would measure in plan view which does not account for elevations. Then measure it in profile view which does account for elevation differences.

Re: problem with Length

fcernst — Sun, 06 Mar 2016 22:23:37 GMT

Your problem is at the beginning.

See attached spreadsheet also.

Re: problem with Length

fcernst — Sun, 06 Mar 2016 22:51:05 GMT

Actually see this attached spreadsheet.

Also using the Auto Corridor feature line is failing you for this analysis. It does not pick up all 249 PVI's

Re: problem with Length

Pointdump — Sun, 06 Mar 2016 23:03:26 GMT

Good catch, Fred!

Dave

Re: problem with Length

fcernst — Mon, 07 Mar 2016 00:10:16 GMT

Check..meant to say _AeccCreateFeatureLineFromAlign

Re: problem with Length

Jeff_M — Mon, 07 Mar 2016 00:20:11 GMT

Fred, there are a number of duplicate PVI's which the AutoFeatureline omits. So the only real issue is that the profile does not start at the alignment beginning which forces the featureline to begin at 0 elevation. Setting the profile to start at 0+000, holding the start slope, then the properties reports a 3d length of 1002.038

Re: problem with Length

BrianHailey — Mon, 07 Mar 2016 00:21:00 GMT

@Pointdump wrote:

Brian,

"... if a pipe is put in the ground at a slope of 5% and has a horizontal length of 100m, the actual 3D length is 500.62m."

500.62 sounds kinda high. Would that be for a slope of 5% off of Vertical?

Dave

If the pipe has a slope of 5%, over 500m it will rise 25m. The actual length of the pipe would be sqrt(500^2+25^2)=500.62.

Re: problem with Length

fcernst — Mon, 07 Mar 2016 00:53:10 GMT

Jeff,

Where are the duplicates?

Re: problem with Length

Pointdump — Mon, 07 Mar 2016 00:53:35 GMT

Brian,

"...a slope of 5% and has a horizontal length of 100m, the actual 3D length is 500.62m."

I'm a pretty fair mathemetician. Read your post again. I was attempting to be funny.

Dave