Triangulation in SU

Thanks for clarifying that. As a surveyor, I probably should have known the distinction. However, I am a building surveyor not a land surveyor. That’s my excuse and I am sticking to it!

I do use levels a step up form a dumpy but I have never used a theodolite. It would be difficult to use an ordinary level to measure angles with any great accuracy but I believe theodolites are another matter. They can measure points in 3D and presumably do that with a combination of horizontal angles, inclination angles, and distance measurement.

Most of what I do just involves distance measurement, so trilateration presumably describes that whereas a theodolite would be using triangulation. Mind you, I have never heard a surveyor here in the UK use the term trilateration - even land surveyors!

Another option is the ‘True Intersections’ feature in TIG’s TrueTangents v3.0

Native true arc intersections would be a worthwhile goal for SketchUp development.
It stands to reason 21st century software should be capable of a task accomplished for centuries with far simpler tools.

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I couldn’t agree with you more. It’s such an obvious omission.

I have tried that out and it works very similarly to Circle Intersect. But it suffers from the same problem of having to start with geometry (that may only be temporary) and forcing you to zoom in to find the cpoint.

I wonder whether there could be another answer to this. I appreciate why circles and arcs in SU cannot be true, but what about construction lines? Would it be possible to have circular construction lines and then have true intersections to click on? This has come up before, such as here. Also @DanRathbun wrote in another post that they have been requested from SU before.

I think it’s a matter of logical order.
The arc entities must exist before one can execute the math determining their point of intersection.

I’ve used Bur’s Trilateration for years, then TIG’s True Tangents. Both can create a lot of extra guides.
@slbaumgartner’s elegant Circle Intersect does the job quickly, without all the clutter.

The time it takes to navigate to the guide point depends upon technique.
Scroll wheel zooming is OK, but certainly not the fastest way to get from A to B and back.

Zoom Window, Zoom Selection, Zoom Extents and Previous position the camera instantaniously.
Creating easy to reach shortcuts for them speeds navigation.

And maybe some additional scenes of where to expect intersection(s).

Although I would prefer true guide circles and true guide arcs
They would be entities on on their own, not creating any new geometry. But “due to” true intersections with same type or with real geometry it would solve many problems, eliminating all these workarounds with temporary intersection “Pie” arcs and plugins on the subject.

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Seconded!

ADD (2018-11-07) link to Feature Request discussion topic:

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This topic is under the Extensions tag but has evolved into a Feature Request. Should it be moved to have a better chance of SU developers seeing it?

Dear Simon,

In the meantime, while a useful ruby to do your trilateration surveying is being developed please give SolveSpace - Download a try.
-Start with drawing a single line, dimension it, change this dimension into the value you wont it to have.
The line will scale automatically
-now approximately sketch the rest of your floor plan to scale.
-Triangulate this face ( for accuracy) into as blund as possible triangles.
-Now dimension all remaining lines, change the dimension to the wright ones as you go.
-Export the file as DXF ,and import into Sketchup

Voila!

For anyone following this topic who is interested, I have added a beta trilateration tool to my circle intersect extension. It does not require drawing circles or arcs and adds only guide points and guide lines to the model. If you are interested in testing it, please let me know.

Just to add to Steve’s post, the new element in his extension works exactly as described in the OP. It’s really easy to use and will surely make drawing up surveys in SU a whole lot easier.

I like to try.

Check your PMs.

I have just published an extension, SB Trilateration, at SketchUcation based on the discussion in this topic. It solves both 2D and 3D trilateration problems precisely without the user needing to first draw circles or spheres.

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Great help for surveyors.

It’s a huge improvement on everything that has gone before.

I’m using Triangle Tool, by Christian B. It works a dandy!

thirded

I have just downloaded and tested this extension. It’s certainly a neat way of drawing triangles. However, for mapping points in space, it has the drawback that you would have to go round afterwards eliminating a bunch of unwanted lines. For my purposes, SB trilateration is the better tool.

I wrote my extension to place guide points instead of actually drawing triangles for two reasons:

  • Provided the input side lengths yield any solution and don’t add up to exactly the length of the reference line, there are always two solutions. So if the extension draws a triangle, it must either draw both possibilities or somehow automatically choose between them. Drawing both is fraught with potential issues because SketchUp will cause the new edges and faces to merge with pre-existing ones, permanently altering them. I believe that Triangle Tool dynamically marks the vertices the user selects as A and B, and uses some rule such as right-hand circulation to decide which of the two solutions to draw. At the time, I didn’t think there was much effort saved by making the user remember such a technical rule (with the risk of having to undo and try again) vs just placing guides and letting the user draw. Maybe that was wrong? See more below.

  • There are use cases in which you only want to know the location of the intersection, you don’t actually want to draw triangles. For example, to know where to place a building using distances from ends of a baseline. There isn’t necessarily any geometry, let alone a triangle, joining the baseline to the building. It is easy to delete all guides without any impact on other geometry, much messier to delete triangles that are no longer needed - especially if they intersected other edges and faces.

It wouldn’t be hard to add a mode to my SB Trilateration extension so that it would draw triangles vs guide points; after all, it has all the required info. As noted above, the main issue would be to provide a simple way to control which solution is drawn. The vertex order-of-selection technique works but is perhaps a bit subtle and technical. Maybe a keystroke or click that would toggle between the two alternatives for a given set of data?

Not quite. Once you have input the line lengths for the two sides of the triangle that are not its base line, there is then the dynamic ability to select orientation. Clicking locks it. That is actually quite neat, at least for 2D trilateration.

As you have pointed out, drawing actual triangles that may then merge with other geometry and having to delete them is a pain when what you are trying to establish is actually a point. Your extension has the edge for me and of course includes the option of 3D trilateration. The only thing I might change is having to have two extensions (2D and 3D) in the menu rather than, say, choosing Trilateration and then selecting between 2D and 3D. It’s a minor point but could save clogging up the menu.