Changing the UCS Origin

Changing the UCS Origin

This video demonstrates how to easily set a new drawing origin to facilitate the location of objects with respect to other objects.

Transcript of this video

Welcome. I’m Cindy Dunn, President of CCAD inc. This video demonstrates how to easily set a new drawing origin to facilitate the location of objects with respect to other objects.

Underlying every AutoCAD drawing is a Cartesian coordinate system. A coordinate is set of numbers that locate the position of a point. AutoCAD utilizes a three-dimensional coordinate system where points may be entered as two-dimensional (X,Y) or three-dimensional (X,Y,Z) values. This configuration is called the World Coordinate System (WCS). The WCS is fixed and cannot be changed.

In a two-dimensional Cartesian coordinate system, X coordinates are arranged along a horizontal line or axis (X Axis). Y coordinates are set along a line perpendicular to the X Axis, called the Y Axis. The intersection of these two axes is called the Origin. The value of both X and Y at the origin is 0.

Positions in the coordinate system are specified by pairing the X location followed by the Y location. The X component always comes first and the X and Y values are separated with a comma. The location of the point will be relative to the Origin of the Coordinate System. Example: 2,4.

AutoCAD provides a display aid called the User Coordinate System Icon (UCS Icon) that helps orient you to the coordinate system. The letters are located at the positive end of the axis of the UCS Icon.

The UCS Icon is typically displayed at 0,0 called the Origin. However, the User Coordinate System (UCS) can be defined to assist in locating points using a different origin and the UCS Icon can be displayed at the Origin.

In this example, two new circles are to be drawn. The centers of the new circles are located in relation to the center of the polygon. Instead of drawing lines and offsetting them I will change the Origin of the drawing to the center of the polygon and input coordinates to locate the two new circles.

First I select the UCS icon. If the UCS icon isn’t visible, go to the View tab, Viewport Tools panel to turn it on. Next I hover over the square grip of the UCS Icon to display a menu of choices and pick Move Origin Only. AutoCAD 2016 includes a new object snap called GCEN (geometric center). Next I press and hold the Shift key and right-click and choose Geometric Centerfrom the menu. Select the edge of the polygon to assign the new UCS origin. If the UCS icon doesn’t jump to the origin, hover over the icon, right-click and select UCS Icon Settings, then Show UCS Icon at Origin.

Now that the UCS origin is located at the geometric center of the polygon I can use absolute coordinates to locate my circles. Absolute Coordinates are located from the origin of the current UCS.

I select the Circle > Center, Diameter button in the Draw panel. When prompted for the Center point I type 3.75,2.25 and press ENTER, then the circle’s diameter. The circle is located to the right (positive X direction) and up (positive Y direction) from the origin. The next circle is located to the left and down from the origin, so both the X and Y coordinate values will be negative (-2.25,-3.75).

In closing, assigning the UCS origin to a reference location can facilitate locating new objects and moving or copying objects to a position relative to other objects in the drawing.

Thank you for watching this video changing the UCS origin. Please visit our AutoCAD Training page or see more of our free Tutorials.