topic Re: Offset alignment with offsets defined at particular points merging continuou in Civil 3D Forum

Offset alignment with offsets defined at particular points merging continuously

Thomas.nowakNUQZB — Tue, 16 Jul 2019 22:38:43 GMT

Hello,

I a list of stations and offsets of an alignment that I have plotted as COGO points. I need to create a continuous line (can be a polyline, feature line, or alignment) that links these points together, but follows the geometry of the alignment, so the connections won't be straight lines - they will follow curves, increasing or decreasing in offset width based on the points they are matching.

I can basically already accomplish this by using the LOFT command and following the alignment as a path, but this is tedious and unreliable. Does anyone have a better solution to this problem?

Things I have considered:

Creating a corridor with a single link and making regions at every point I need to change - But this procedure is very time consuming. I just need a plan-view line.
Using the "Offset Alignments" tool - this almost gets it right, but the problem is that there is never a "region" with a particular offset width - the offset width from the alignment is constantly in flux, from point to point along the alignment.

Re: Offset alignment with offsets defined at particular points merging continuou

tcorey — Wed, 17 Jul 2019 11:51:31 GMT

Are you aware of the Add Widening command? Type ADDWIDENING or find it on the ribbon after selecting an Offset Alignment object.

I think this will work for you. It lets you edit an Offset Alignment with widening regions and grip points.

Re: Offset alignment with offsets defined at particular points merging continuou

Thomas.nowakNUQZB — Wed, 17 Jul 2019 13:49:46 GMT

Yes, I've tried this method, but the problem I find is that it applies a uniform widening with tapers on both ends. The start and end points along the alignment have different offsets, so I don't need a uniform offset width - I need an offset with a constantly changing offset.

Ideally, I'd like to go from point A to point B to point C to point D, etc., changing the offset width as the line goes along the alignment from point to point.

Re: Offset alignment with offsets defined at particular points merging continuou

wpagl452 — Thu, 25 Jul 2019 22:38:26 GMT

Hi @Thomas.nowakNUQZB.

In the image you posted, the points appear to be a constant offset from the main alignment; is this not the case?

If the offset alignment will exactly follow the path of the parent alignment, offset the alignment to create a polyline with the same geometry.

Re: Offset alignment with offsets defined at particular points merging continuou

Thomas.nowakNUQZB — Mon, 29 Jul 2019 13:00:14 GMT

Hi,

That's the issue. The offsets are never the same. I can't just offset because that creates a parallel line. I need a line that is able to constantly taper while still being aligned with the main alignment. The offset alignment tool would work if I could toggle off the tapers at the ends and set the offset to taper between points.

Re: Offset alignment with offsets defined at particular points merging continuou

wfberry — Mon, 29 Jul 2019 14:33:10 GMT

Why not just target a feature line through these points?

Bill

Re: Offset alignment with offsets defined at particular points merging continuou

cwr-pae — Mon, 29 Jul 2019 15:56:08 GMT

Depending on your reporting/labeling requirements this can be done with a widening if the rate change in the offset is a constant value. Setup a widening using default values. Set the end transition length to 0.001, set the widening length to 0.001. Set the start transition to the alignment length minus 0.002. You will probably have to play with it to get the right results. Or you can use a feature line from the alignment and a grading transition to specified widths to create a feature line.

Re: Offset alignment with offsets defined at particular points merging continuou

samir_rezk — Mon, 29 Jul 2019 16:08:19 GMT

Hi @Thomas.nowakNUQZB

perhaps a a best fit alignment from your set of cogo points may meet your criteria a little better than an offset alignment. Just a thought!

Re: Offset alignment with offsets defined at particular points merging continuou

Thomas.nowakNUQZB — Wed, 31 Jul 2019 17:33:51 GMT

Hi Bill,

Because the line is not going straight from point to point. The line should follow the alignment and taper from point to point while still being aligned to the alignment.

Re: Offset alignment with offsets defined at particular points merging continuou

Thomas.nowakNUQZB — Wed, 31 Jul 2019 17:35:33 GMT

Hi,

So by feature line in this case, do you mean creating a feature line in a corridor? How do I go about just creating a single point in an assembly and modifying that based on my COGO points as I go along the alignment?

Re: Offset alignment with offsets defined at particular points merging continuou

Thomas.nowakNUQZB — Wed, 31 Jul 2019 17:36:36 GMT

Hi,

Best fit would not be exact. The lines need to go exactly through the points I specify at the correct widths, and taper linearly along the alignment from point to point.

Re: Offset alignment with offsets defined at particular points merging continuou

wpagl452 — Wed, 31 Jul 2019 22:24:33 GMT

Can you show an example of the finished product that you've manually made?

Re: Offset alignment with offsets defined at particular points merging continuou

cwr-pae — Wed, 31 Jul 2019 22:41:54 GMT

See the grading menu for commands (menubar=1 to turn on menus). Create a FL from your alignment. Create a transition grading along that FL with the target criteria as distances equal to each offset needed. This will create a FL that is derived from the alignment/FL at the transition distances specified.

Re: Offset alignment with offsets defined at particular points merging continuou

Thomas.nowakNUQZB — Fri, 09 Aug 2019 14:42:03 GMT

Hi,

This is a basic example of what I want. The white lines that offset from the red alignment are the specific offset points. The curved white lines are what I accomplished using the LOFT command, using the alignment as the path. So, the white lines use the alignment as a guide while continuously transitioning in actual offset width from point to point.

My issue with using this method is that it often gives me an error when working around spirals. And it's only ever worked in 2D. I'd much rather have this modelled in a corridor somehow so that it can be faster and then I can verify any point by using the section editor.