What Does The Tilde ~ Mean In Measurements?

When drawing dimensions, the tilde ~ pops up every once in a while.
What is the significance of this?
Why does it usually signify the shape I am dragging out will change when I hit ‘enter’ ?

It means that the dimension is approximate. The actual dimensions falls between the intervals of your selected Precision. If you want precise dimension, enter them instead of trying to drag out the shape to the dimension.

Look at Model Info > Model Units
Change to a greater precision.
Otherwise type in the exact size as you ‘draw’…
For example to draw a line exactly 1234mm long, click to set the start point, then drag the end point until it’s ~1200mm showing in the Measurements box, and then type 1234mm + [enter] - don’t click in the Measurements box, just type…
If you are working with ‘mm’ set as your Model Units there’s no need for the final ‘mm’, BUT if you are working in some other units then you need to tell SketchUp you want ‘mm’.
So if you are working in feet/inches but want something drawing that is exactly 1234mm long, then there’s no need for complicated mental arithmetic, just type in 1234mm !

Thanks for the question and the answers.
Makes me think the model needs to be drawn with an workpoint benchmark as an absolute reference as some construction sites are laid out with.

How concerned should I be with Tilde measurements? For example, if I want a dimension to be 20Ft. and the Entity Info box shows it as ~ 20’ … will that reach up to bite me in the rear later on? Should I try to re-work the model until the ~ disappears or can I let it go?

I’m working strictly with architectural drawings - no precision machine work.

You should be typing your dimensions in, not depending on getting your cursor close enough.

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Very likely those ~'s will come back to haunt you later. It does depend on what you need out of the model.

The location on the site is probably not that critical but as you model the building, you should be entering exact dimensions to avoid the tildes. My preference is to model with Precision set very high so I can see dimensions that might not be accurate. That doesn’t mean that I’ll intentionally model things with 64ths but I want to see them if they occur.

If you need to rework some things, you can try a method I’ve used to save time. I tend to draw a rectangle around the boundaries of what I’m working on, then use the tape tool to lay down construction lines, typing in the exact dimension. For example, if I’m drawing a building, I draw the outline, then set construction lines parallel to the sides to show where the walls need to be placed. You could do the same thing, and simply move your objects to the construction line. It may help. Also, use the rectangle tool whenever it make sense to save your walls from being out of square. Two rectangles cannot be out of square with each other in SU unless you intentionally rotate one of them.

One thing not mentioned in this thread: Always turn off Length Snapping (Window menu>Model Info>Units). It is an useless feature causing slight inaccuracies that is by default on in most templates. No one who has used SketchUp seriously can see any utility in it.

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I agree with Aussi. This Length Snapping feature shall be turned off by default in all the templates that come with SketchUp.

That is rather alarming that snapping is inaccurate! I often have it set to 0.3m for initial planning and 0.1m for basic construction modeling… is there some fundemental arithmetic bug in it that causes this inaccuracy or are you really refering to a risk of user input error? Linked to the basic unit being Imperial…?

I think that SketchUp’s length-snapping is very precise, and does exactly what it’s designers intended - which is generally NOT what users expect (nor is it very useful). That is what causes trouble. Users seem to expect that the feature acts as a sort of universal 3D grid, constraining end points to that grid anchored at the world origin or something. But that is not how length-snapping works. Length-snapping ensures that the length of an edge (and probably the radius of an arc or circle) is an exact multiple of the specified length. If the edge is started at some odd position or aligned in some odd direction, then the end point of the edge will be an exact multiple of the chosen length increment away - but which may also be at some odd location.

Consider the following examples with the snap increment of 1/2 inch.

  1. If an edge is started at the world origin and projected along the red axis, the second end-point of that edge will be an exact multiple of 1/2 inch away, and thus the second end-point will be at a location that is a multiple of 1/2 inch along the red axis, and the length of the line will be a multiple of 1/2 inch. OK, fine.
  2. If a second edge is started at the world origin and projected along some arbitrary angle, the second end-point of that edge will be an exact multiple of 1/2 inch away (and the length of the line will be a multiple of 1/2 inch), but the location of the second end-point will be at some odd coordinates.
  3. If a third edge is started about 1/16 of an inch along the red axis from the world origin (the snapping feature does not prevent this), and projected along the red axis, the length of the third edge will be an exact multiple of 1/2 inch but neither end-point will be at a multiple of 1/2 inch coordinate point.

Another observation: Length Snapping is immediately overridden by any inference so if you start an edge at an arbitrary point and end it somewhere where an inference is active, your click will follow that inference even if it results to an arbitrary length or angle.

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