Why, when I move polyline in AutoCAD it changes the polyline elevation? Why when moving COGO Points in Civil 3D they lose their elevations? When I copy objects in AutoCAD they change their elevations, why? The answers to these and other questions related to Elevations and Move in AutoCAD will be answered here!
AutoCAD Elevation OSNAP
The system variable OSNAPZ was introduced back in AutoCAD 2006 version. It controls whether object snaps are automatically projected onto a plane parallel to the XY plane of the current UCS at the current elevation. According to Autodesk’s site. Or in simpler words, OSNAPZ controls whether the objects/cursor will Snap and change the Z value (elevation) of the object.
To copy or move without changing the election, type on the command line OSNAPZ and enter 0.
OSNAPZ, 0 - Osnap uses the Z-value of the specified point
OSNAPZ, 1 - Osnap substitutes the Z-value of the specified point with the elevation (ELEV) set for the current UCS
If you found this information useful. Don’t forget to check our other AutoCAD Tips for more great Tips and Tricks just like this one!
When to use it
This matters whenever you move or copy objects that already have correct elevations, such as polylines, feature lines or COGO points on a grading or drainage drawing. If the Z values change after a simple Move or Copy, the object snap is the likely cause. Fix it before you continue working, so you do not end up with flat or wrong elevations that are hard to notice later.
Tips and common mistakes
- Type OSNAPZ and enter 0 to keep the Z value of the point you pick. Entering 1 uses the elevation set for the current UCS instead.
- Check the elevation of one moved object before you move the whole drawing. A quick look at its properties shows if the Z value changed.
- Do not assume the objects are broken. Often the elevation was only replaced during the move, and the setting is the real problem.
Related tutorials
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