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How to straighten out Survey Figures or Feature Lines

ryancj31
(@ryancj31)
50+ posts Member

I absolutely realize this may be borderline OCD but for a while now I’ve been straightening out my breaklines in my topos. Whether they be survey figures or manually drawn feature lines.

This is coming from someone who does a fair amount of design and grading using C3D grading tools and methods. As a designer, it’s nice to have nice straight curbs or edges of concrete to work with. It minimizes some pesky triangulation issues and allows for more time to get frustrated with other C3D grading problems. 

My current method is to use the best fit line tool and select all the Cogo points that I think should be in a perfectly straight line. I then draw a polyline from the point (getting the elevation) perpendicular to my best fit line. I then move all those points to the endpoint of that polyline (keeping its elevation intact). Erase said polylines. Draw featurelines.

With most surveys the deviation of those points to best fit line rarely exceeds 1”. Sometimes surprisingly lower. So I have no qualms in fudging my breaklines a bit.

I’m slow at many other things but I’m a fast drafter so this rarely takes more than 30 minutes but the task is getting old.

So my question is, is there some existing C3D tool that does this and I’m just overlooking it? A lisp routine somewhere? Trimble Business Center?

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Topic starter Posted : July 28, 2022 5:10 pm
Jacob Wall
(@jacob-wall)
100+ posts Member

Not aware of any existing tools that does that, but it is an interesting idea, and when I have time I do enjoy LISP programming. Time is scarce these days, but to explore this further...

I don't use C3D, so I am thinking of 3D polylines for a possible workflow.

  • Run command
  • Select 3d polyline
  • Dialog pops up where you can select whether to best-fit vertices in horizontal and/or vertical, and a threshold distance to enter for both hz and vt.
  • Command iterates over vertices, first hz and then vt, does best fit computations incrementally until a new vertex causes threshold to be exceeded, then computes best fit geometry up until vertex that caused the fail. Next a new best fit computation begins again (if necessary)
  • Prompt asks whether to delete original 3d poly
  • Draws new 3d poly

So the resulting 3d polyline could have multiple vertices to take care of grade breaks (vt) or curves/bends (hz). I suppose an option to densify vertices along the final polyline might be useful also.

Is that close to what you had in mind? Further thoughts?

This post was modified 1 week ago by Jacob Wall
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Posted : July 28, 2022 6:02 pm
ryancj31
(@ryancj31)
50+ posts Member

@jacob-wall it sounds like your outline covers the basic operations of the task. 

I can write some pretty basic lisp routines and know enough about them to know that a routine that could do all of this is way beyond my abilities. However I also know enough about lisp to know that this is possible with minimal user input. 

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Topic starter Posted : July 28, 2022 6:35 pm

Jacob Wall
(@jacob-wall)
100+ posts Member

Ok, no promises but will try to seek out some time for this in the next month or two. I do quite a bit of topographic work also so this could come in handy sometimes for our in house needs.

Would be curious also if anyone knows of an existing tool that already does this. Not against reinventing round objects, but when time is scarce then the time value of money concept gets a re-evaluation.

This post was modified 1 week ago by Jacob Wall
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Posted : July 28, 2022 8:38 pm
Dave Drahn
(@dave-o)
100+ posts Member

This may not be any quicker, but first thought is the Elev by Reference tool.  It can be a little confusing, but once you get on a roll it can go fairly quickly.

Set you running snaps to Nod

Make sure your point style has the 3D geometry 'Point Display Mode" set to "Use Point Elevation" (as opposed to flatten)

Draw a featureline from end point to endpoint (setting the ends at your straight line end elevations)

Select it.  Hit the Elevations by Reference button.

Select the nod of the point that's slightly off line. Grapghics will display to nearest fl endpoint but don't use it. Instead,

Select "Insert".  This will let you drag the new elevation point to an "eyeball perpendicular" to your offset point.

Click to set new elev pt.

On the command line, type 0 for a zero grade between your offfset pt elevation and the new elevation point,

<Escape> and your featureline is still selected to hit the "Set Elev by Reference" button and pan up to the next one.

Seems laborious but in a flow it ends up Select, click, click, "I", click, "0" enter, esc for each one.

If you can see the video, I've also discovered a new expression that shows up there to use for a new Line and Curve Label (that I've added to my template).  I've named it "Grade and Elevation" and in multiple segment mode it adds grade between FL nodes and a little elevation at each endpoint.  They're dynamic so they update with a change to the FL.  Super helpful for keeping an eye on them during design.  Easy to delete when done.  Happy to share if you'd like.

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Posted : July 28, 2022 10:06 pm
Rover83
(@rover83)
1,000+ posts Member

Here's a method that is a bit goofy but will work and minimizes manual editing of entities.

1. Draw 3D polyline between all of your points.
2. Use the Stepped Offset/Offset Feature command to offset it on both sides by a few feet.
3. Create a temporary surface and add the offset 3D polylines to it.
4. Delete the center 3D polyline and run the best-fit line command.
5. Rather than manually draw perpendicular lines between the points and the best-fit line, use the "minimum distance between entities" command to draw them.
6. Move points to endpoints on best-fit line.
7. Use the "Elevations from Surface" command to just pop the elevations from the temp surface back to the points.

8. Delete everything but the points. Now they're in a line and still have correct elevations.

Takes a bit of getting used to but once you have it down it goes a lot faster.

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Posted : July 29, 2022 7:28 am

BlitzkriegBob
(@blitzkriegbob)
200+ posts Member

Why do you have to move the points? I ask this as someone who would not ever do that. When you get your best fit line, turn that in to a feature line and then have it get elevations from your surface. Does that not accomplish the same? 

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Posted : July 30, 2022 5:26 am
MightyMoe
(@mightymoe)
5,000+ posts Supporter

If you're wanting to move located points in a field survey it's simple. Don't do it. 

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Posted : July 30, 2022 6:19 am
ryancj31
(@ryancj31)
50+ posts Member

I understand your hesitation @blitzkriegbob. I do it because my cogo points become plotted spot elevations. I want those to actually be on the line. 

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Topic starter Posted : July 30, 2022 9:17 am

BlitzkriegBob
(@blitzkriegbob)
200+ posts Member

I rarely show spot elevations, but if I was asked I would just make a surface label and label the points along the feature line. I just have a thing about moving surveyed points, and I think most surveyors would feel the same.

I'm more of a road guy than a site guy, but I do grading occasionally. What I described is what I do. I get the OCD. I am also, but sometimes you just have to remind yourself this isn't a perfect world. Moving surveyed points an inch or so isn't going to make the design any better. YMMV! 

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Posted : July 30, 2022 12:11 pm
ryancj31
(@ryancj31)
50+ posts Member

And we mostly do site design. My boss loves him some spot elevations. I mentioned before on this site that we routinely label both top and bottom of curbs and many were flabbergasted. It makes for some congested maps but I think the construction crews really appreciate that extra detail. As do surveyors making points to stake it out in the field. Especially when you have 3-4 different curb types on the site and numerous curb cuts and tapers.

I get what you are saying about moving survey points.

My spot elevations for curb and gutter are actually surface labels (to get an easy to use singular label with top and bottom elevations stacked) whereas any others are just cogo points with the spot elevation style. It always bothered me to have 2 types of labels for these. Maybe I’ll just tryout using all surface labels and place spots along the best fit feature line and leave my cogo points in their original position.

But even that discrepancy still bothers my OCD a bit. Oh well. 

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Topic starter Posted : July 30, 2022 12:54 pm
RobertUSA
(@robertusa)
200+ posts Member

This is existing conditions are you are concerned over a 1 inch deviation in a curb line??? You might be in the wrong job if you are “calculating” to draw existing features..which as the exist on the ground are not a perfect straight line. Tell your supervisor what are doing and hopefully they tell you to stop!

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Posted : August 3, 2022 1:00 pm

Jacob Wall
(@jacob-wall)
100+ posts Member

If you ever had two crews pick up the same top of curb and gutter, chances are there will be measurable differences between the two datasets, could be more than an inch even. Therefore, no topo pickup is perfect IMHO, and in order to create a nice model it can be useful to have a quick and efficient way to perform some best-fit calculations to straighten things out. Automated tools are faster than doing it manually. This is what the OP was referring to I believe, and certainly I share the appreciation for doing that. Heck, without some sort of massaging, it is often impossible to build a reliable TIN surface from field measurements (depends on attention to detail and the skill of field personnel). If you don't have a reliable TIN surface then your contours will not be accurate either.

As I'm pondering this further it occurred to me that the same routine would also have other applications. For example, if you go survey the existing centerline of some dirt road and you want to design an alignment that follows the existing path fairly closely. With the type of LISP program that was already discussed, you could take the 3D polyline connecting all the centerline points and by increasing your tolerances you could create a much more simplified geometry based off of real measurements. By adding in parameters such as min/max radii for curves, min arc lengths, options to force curves tangential, etc, the program would make quick work of that.

So, the question then is, does C3D already have such a tool for creating centerline alignments from points? I don't use C3D but it seems plausible that this already exists.

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Posted : August 4, 2022 10:14 pm
BlitzkriegBob
(@blitzkriegbob)
200+ posts Member

Rereading the original post, if what you are looking for is a routine that speeds up moving points, you could look at SincPac as they have a Move Points command that might help you. There may be other routines in there that may interest you. They also have a free trial.

I know you probably were looking more at the actual best fit lines rather than moving points, but I think using your routine is as good as it gets. 

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Posted : August 5, 2022 6:59 am
ryancj31
(@ryancj31)
50+ posts Member

@robertusa So as I think back I believe I started down this rabbit hole when I was trying to use codes in the field to shoot in curves. Many data collector programs and C3D have a routine for defining a best fit curve. There's a few ways to perform this and it seems to be a generally accepted practice to use a best fit curve on stuff like a 30' radius curb return (as opposed to having multiple arc segments of varying radii and tangency). 

That got me thinking, hey if my 2 shots on the "tangent in and out" of my curb were off 0.0whatever' from the true "best fit line" my curves might not be as accurate as they could/should be. If one of those shots was indeed off by .08' you may have a pretty hard time making a curve look right. Once I started doing a best fit line of the "straight" lines my curves seemed to work out much better.

I've even noticed that once I do a best fit line for each of the tangents and fillet them with a nominal radius of, lets say 30.00' again, the resulting curve hits all of my shots on the curve within a very acceptable tolerance (less than an inch). Sometimes that nominal radius is not quite acceptable and I will do a best fit curve on my 3 to 5 shots on the curve and then fillet those two best fit tangents with the radius of the best fit curve. Of course, this applies to more recent construction. Some of the older streets around here you can throw all this straightening out stuff out the window and I just draw them up with ugly non tangent curves and all.

I usually create unnecessarily high resolution aerial images to insert in my drawing just because we are lucky enough to have access to them. These help guide me in drafting such things like this. It might be much easier to see where a PC and PT are looking down at a high-res aerial than out in the field. It could be that out in the field I tried to get a shot on what I think is the PC or PT but when I do all this best fit stuff my shot seem to be off a foot or two so longitudinally speaking. Looking down at the aerial I can see - yeah maybe that PC didn't start right at that joint.

Our concrete guys down here do pretty good work. I know I could see an inch of deviation with my eye looking down a 100' stretch of curb. I've seen topos by others where there is more than an inch in deviation from someone's points on a "straight line". I go on site and she's straighter than an arrow.

It is quite difficult to get the tip of your rod in the exact same spot on the curb line every shot and I'm not using a bipod on 200 curb shots and spending the time to get perfectly plum on every curb shot as I would with a property corner. And I believe it to be impossible to get your tip the "true" top back of curb since there's going to be a slight radius or round-over on that concrete (I actually want to make a special tip for shooting edges of curb and concrete). I feel my job is to provide the most accurate representation of the existing conditions as practical. Not just dump points and connect the dots.

Another thing I've noticed throughout the years is some peoples shots on something like a 5' wide sidewalk. Lets say there is tough thick grass and weeds growing over the edge of the walk. I try to kick the grass and weeds away until I can see the actual edge of concrete. Somedays my toe hurts from so much kicking. Maybe I'll take a few pokes through the weeds until I can feel the true edge. Not everyone does that. When I put in the extra effort to find that true edge I find the width of the concrete walk to be a nearly perfect 5' wide. Anywhere I lay my tape on the sidewalk I measure 5.00'. Okay maybe 4.97'-5.03' but i'm calling it 5.00'. I've measure the distance of some peoples shots to say its a 4.85' wide sidewalk. Or maybe even 4.6' on a bad day. Are my best fit lines exactly 5' apart a better representation of the existing conditions? I feel so. Again, this applies to more recent construction but not necessarily every new and shiny site.

To each is own, and I do appreciate the concern as it makes me review my whole process, but I see no harm in fudging these shots within a reasonable tolerance. I do a lot of design and grading. I sit next to someone who does mostly grading. I hear the complaints (admittedly minor and nearly negligible) and try to find a way to resolve them or improve the quality of our topos for use in the modern world. My boss on the other hand who does all of his grading on paper with a scale, a pencil and a calculator has no idea that inch of deviation is there. But someone who grades with software such as C3D may notice such a thing. Will it ruin their design? No. Will fixing such a thing help their workflow? Maybe. Will fudging a curb line .04' set someone up for disaster? I can't think of any situation where it could.

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Topic starter Posted : August 5, 2022 9:08 am

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