Coordinate Systems (UCS & WCS)

AutoCAD uses two coordinate systems:

• World Coordinate System (WCS)
  
  In this type of a coordinate system, the X axis is horizontal, the Y axis is vertical and the Z axis is at 90 degrees to the plane formed by the X and Y axis. The origin is the intersection point of the X and Y axis, i.e. (0,0), which is always at the left bottom side of the drawing.
  
• User Coordinate System (UCS)
  
  To facilitate changes in direction of the plane that one is working in, the UCS has been developed. The direction can be seen in the form of a grid by pressing F7. The UCS is defined in terms of the WCS

The UCS can be relocated in the following ways:

o By defining a new origin
o Rotating the UCS around any one of the axis. That is, the direction of one of the axis is fixed while the other two are interchanged.
o Loading a saved UCS
o Specifying the direction in the direction of the present view or by aligning it with an object

Once the UCS has been relocated, Snap, Grid, and Ortho modes all rotate in line with the new UCS.