SketchUp Accuracy

SketchUp Pro
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1

Hi

I am working on a project with multiple other professionals. We are the only ones using SU. The others are on ACAD. I seem to have a consistent problem with SU accuracy output. Whatever gets exported from SU is always several millimetres different when overlaid in CAD.

So an engineer sent me his grid layout for columns. I overlay this in ACAD with other people’s files and everything overlays perfectly.

I import the ACAD file into SU and draw over it with SU tools.
I setup a parallel projection and export a CAD file.
When I overlay the exported CAD file over the original grid layout, it is off.

This has occurred on a couple of projects and I would like to get to the bottom of it. Any ideas?

2

Are you using Standard Views/Top ?

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3

Share an example .skp file so we can see what you are working with and help you diagnose where the problem lies. There’s no reason you shouldn’t be able to make precise models.

Are you still using SketchUp 2019?

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4

SketchUp’s representation of circles and arcs as collections of edges will interfere with precision of round-trip import/export between SketchUp and 2D CAD, especially where an edge intersects a circle or arc. Is that what you are seeing?

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5

Yup, standard “Camera” → “Standard Views” → “Top”…also using “Parallel Projection” under the camera menu.

6

Yup, SU 2019. Although same thing happens in V2023 (which I used on another project)

7

Straight edges become parallel and/or at a different angles to the drawing being overlayed.

8

I could get the model down below 16mb however I would have to remove the CAD file. So I have uploaded to a Google Drive instead.

The problem however presents itself outside of SU - in other CAD programs.

9

Are you sure both - cad and SketchUp - are using the same coordinate origin?

10

How do I check coordinate systems? (I think I know but thought I’d ask just in case I’m overlooking something)

11

hello

if you use the rotate tool, you’ll notice your grid isn’t properly aligned with axes (once you set your reference point with rotate tool, press left arrows to force align to green axe, right arrow for red - here it shows ~0,000 close to it but not quite !)
It is a problem because every time you’ll draw something, sketchup inference system will force you to draw along them (unless you press alt to turn inference off) and everything will be off the grid

off the grid

When you import dwg’s or anything you’ll use as a reference, it is very important to make sure everything’s properly set, otherwise everything will be wrong…

you have multiple possible approaches :

you can import your dwg and manually rotate it
you can use the axe tool (tools menu > axes) so they match the grid and optionnaly save a scene to store new axes
you can edit the imported dwg to make sure you’ll work with its own UCS (User coordinate System) after grouping everything that is in it to avoid interfering with the drawing
you can fix the dwg in autocad because it probably means someone created a new UCS that is slightly off world’s axes.

can you share the dwg file ?