Polyline Elevation Propertie in UCS

[Oscar Fuentes]

When I create a UCS and draw a polyline using it, the elevation value doesn't make sense when I check it. Can someone explain what this value means?

[SLW210]

You need to post the .dwg and give a more detailed explanation.

[Oscar Fuentes]

In this DWG file, we have 4 different UCS. where 4 polylines have been drawn, and two of them show an elevation other than zero.

I don't understand the value 92.8477 for the elevation.

UCS x Polyline Elevation.dwg

[CyberAngel]

When you draw a regular polyline (not 3D) in a coordinate system that is not the World system, it belongs to that system. Whatever the Z coordinate is for that first vertex, that's the elevation for the whole polyline. In other words, the whole polyline conforms to the XY plane for that system. You can draw a polyline in some random coordinate system, and if the first vertex is at Z=0, the elevation will be 0 no matter what the current system is. (I know because I just drew some polylines in random systems.) If you change the elevation, no matter what your current coordinate system is, the new elevation takes effect in the other, original system--the one it was drawn in.

 

When you draw a polyline in the World coordinate system, and the first vertex is at Z=0, the same rules apply. The polyline belongs to the World system, and any changes to the elevation (or any of the vertices) are applied in World coordinates. Those changes will give you the results you probably expected. On the other hand, if you change a polyline that is not in the World system, you may get results you didn't expect.

 

Your next question will probably be, "Can I change a polyline in my new coordinate system so that it has an elevation that conforms with the World system?" The answer is Yes, if you have Civil 3D. Otherwise you'll probably need to redraw the polyline in World coordinates.

[lrm]

In the following image the green plane lies on the World XY plane while the red plane is above it and tilted.  The white polyline was drawn on the red plane by setting the ucs so that it's Xand Y axes were coincident with it.

 

Here's a front view with the World ucs active.

 

Same view but with the UCS of the red plane active.

 

The perpendicular distance from the plane of the polyline to World (0,0,0) is the polyline's elevation.

Note that if the polyline is moved by 0.5 in the z direction of the red plane the elevation changes by 0.5.

 

So the anser to the question "Can I change a polyline in my new coordinate system so that it has an elevation that conforms with the World system?"  is, It  Depends. The UCS of the polyline must be parallel to the world ucs but you would need to also make it coincident to the World UCS!

Edited 1 hour ago by lrm