Author Topic: Vertical Curve elevations  (Read 6267 times)

0 Members and 1 Guest are viewing this topic.

elsos

  • Guest
Vertical Curve elevations
« on: December 06, 2004, 03:48:09 PM »
Does anyone know if LDT has a way to set points for construction on a vertical curve at any desired station / offset?
I cannot find a way to do it. Surprising that this isn't a typical event for LDT.
The only way we've done it is by precalculating the elvevation, and hand entering the points at the stations we want.

Any ideas or thoughts would be cool.

Thanks!

Dent Cermak

  • Needs a day job
  • Posts: 6914
  • Clinton, Mississippi
Vertical Curve elevations
« Reply #1 on: December 06, 2004, 05:09:45 PM »
I haven't done one yet. The only place I have found that address this is the training CD's put out by AGT. They are a little pricey ( but less than a trainning school.) See if your boss will buy a set.

http://www.agtcad.com/
If you are looking to me for answers, you really have problems. Carlson Survey 2016 w/ Embedded AutoCad

elsos

  • Guest
Vertical Curve elevations
« Reply #2 on: December 06, 2004, 05:15:48 PM »
Do you know of a LISP that would do this?

Dent Cermak

  • Needs a day job
  • Posts: 6914
  • Clinton, Mississippi
Vertical Curve elevations
« Reply #3 on: December 06, 2004, 07:32:54 PM »
It's built into LDD, it's just that I haven't figured out how to create the vertical alignment.
There's no need to pay for a lisp routine to do what you haven't figured out yet. It's there, you just need instructions. I don't know if the help files fully address this routine. However, I can assure you that the lisp to do a vertical curve would be involved enough that nobody will write one for free.
If you are looking to me for answers, you really have problems. Carlson Survey 2016 w/ Embedded AutoCad

Jeff_M

  • King Gator
  • Posts: 4040
  • C3D user & customizer
Vertical Curve elevations
« Reply #4 on: December 07, 2004, 02:00:21 PM »
Provided the alignment has the centerline profile with VC defined in the project, it wouldn't be too hard to write a routine to do this.

If you give me a detailed description of the data you have and the desired reslts, I may have a routine that does most of the calcs already.

elsos

  • Guest
Vertical Curve elevations
« Reply #5 on: December 07, 2004, 02:48:34 PM »
I think you need Autodesk Civil Design to be able to have vertical curves in an alignment. Thats another thing Ive wanted to be able to do, but never have figured it out.

The field crews have the ability to create alignments in their data-collectors to generate locations for stakes, but in the office we end up hand calcing points through vertical curves.

Quote
However, I can assure you that the lisp to do a vertical curve would be involved enough that nobody will write one for free.

Yeah, but the time to pre-calc all the darn curves can be cumbersome and time consuming as well.  I used Excell to calc vertical over a couple of bridges, and it tired my noggin... can only imagine how tough it would be to write a program to create points!

Thanks guys.
-Eric

Mark

  • Custom Title
  • Seagull
  • Posts: 28725
Vertical Curve elevations
« Reply #6 on: December 07, 2004, 03:23:28 PM »
Would if we could write a program to calc the X Y ? Not saying I could, but if you have the formulas I'd be willing to look into it.
TheSwamp.org  (serving the CAD community since 2003)

Jeff_M

  • King Gator
  • Posts: 4040
  • C3D user & customizer
Vertical Curve elevations
« Reply #7 on: December 07, 2004, 05:07:49 PM »
Quote from: elsos
I think you need Autodesk Civil Design to be able to have vertical curves in an alignment. Thats another thing Ive wanted to be able to do, but never have figured it out.

Thanks guys.
-Eric


Correct on the Civil part. The actual code for VC's isn't all that involved, provided they are symmetrical VC's. And if you DO have a LDD alignment to work with., which it sounds like you do.

What steps are involved for your current process. Maybe I can whip up something that will at least cut down on the time.

What if I provided a form that you input the Station/Elevation of all GB's (the PVI is also a GB) and the length of VC? This is the part that the Civil module does.
Then in another column you input the Station/Offsets. You'd probably need other inputs for street x-slope, curb height & distance from centerline, gutter depth, etc.....make sure to include all variables.

elsos

  • Guest
Vertical Curve elevations
« Reply #8 on: December 07, 2004, 05:57:29 PM »
Quote
What steps are involved for your current process. Maybe I can whip up something that will at least cut down on the time.
Quote

Currently I hand calc the grade Im looking for and hand enter it on the point I set manually.  I think a form like you are talking about would be the most ideal thing, and to include the x-slope etc.

You mention symetrical, meaning in/out grades the same?

elsos

  • Guest
Vertical Curve elevations
« Reply #9 on: December 07, 2004, 06:02:07 PM »
Oops. Guess I ended up quoting myself  :oops:

Jeff_M

  • King Gator
  • Posts: 4040
  • C3D user & customizer
Vertical Curve elevations
« Reply #10 on: December 07, 2004, 06:24:05 PM »
No, symmetrical meaning the PVI is at the midpoint of the VC. So a 100' VC would have the BVC 50' prior to the PVI and the EVC 50' after the PVI. Asymmetrical VC's allow the BVC/EVC's to vary in distance from the PVI.
 You say you "hand-calc" the elevation....What data do you have/use to get the elevation? Is the elevation you calc the actual elevation at the point or is it the centerline elevation at that station?

elsos

  • Guest
Vertical Curve elevations
« Reply #11 on: December 07, 2004, 06:35:46 PM »
"Hand calc" meaning using a set of prints and it's profile, then with plan cross-slope and basically precalculating elevations at the points I want to give to the field crews. Sometimes I need to get them points at centerline, Back of Curb, manholes etc.

Could do it as fast over the hood of a truck as I do in the office at times.

Without Civil Design, this is the only means Ive found when going through a vertical curve.

Jeff_M

  • King Gator
  • Posts: 4040
  • C3D user & customizer
Vertical Curve elevations
« Reply #12 on: December 08, 2004, 12:40:08 PM »
Well Eric, after some initial layout work and flowcharting what needs to be done I've come to the conclusion that I could write a small routine to insert your points at the Station/Offset/Elevation as desired, but ONLY if you could acquire and use the Civil Design package to create the centerline profiles.

For me to recreate what has already been done would require much too much of my time.

I apologize for leading you on.

elsos

  • Guest
Vertical Curve elevations
« Reply #13 on: December 08, 2004, 12:49:28 PM »
Jeff, please don't worry that you may have led me on, that only brings back memories of High School :shock:

It does sound like a tall task, and Im sure there is a program out there that already does what we're talking about, just need to decide what direction to be heading from that standpoint.

I really appreciate all the thought you've run with me on this though!

Thanks!

Bob Garner

  • Gator
  • Posts: 2902
Vertical Curve elevations
« Reply #14 on: December 09, 2004, 10:05:11 AM »
I recall from my old surveying days that a vertical curve is a parabola with the equation t = ax^2 where t is the offset of the curve from the tangent, and a is a constant defining the rate of slope change.

Maybe it's cheating, but I just draw a spline curve tangent to the tangents at the BVC and EVC and bisecting a vertical line from the PVI to the chord between the BVC and EVC, then I just measure off the elevations of points along the curve.

Bobber