2004

210 | Chapter 15 Use Precision Tools
Use Coordinates and Coordinate Systems
For precise coordinate input, you can use several coordinate system entry
methods. You can also use a movable coordinate system, the User Coordinate
System, for convenient coordinate entry and to establish drawing planes.
Overview of Coordinate Entry
When a command prompts you for a point, you can use the pointing device
to specify a point, or you can enter a coordinate value on the command line.
You can enter two-dimensional coordinates as either Cartesian (X,Y) or polar
coordinates.
Cartesian and Polar Coordinates
A Cartesian coordinate system has three axes, X, Y, and Z. When you enter
coordinate values, you indicate a point's distance (in units) and its direction
(+ or -) along the X, Y, and Z axes relative to the coordinate system origin
(0,0,0).
In 2D, you specify points on the XY plane, also called the construction plane.
The construction plane is similar to a flat sheet of grid paper. The X value of
a Cartesian coordinate specifies horizontal distance, and the Y value specifies
vertical distance. The origin point (0,0) indicates where the two axes
intersect.
Polar coordinates use a distance and an angle to locate a point. With both
Cartesian and polar coordinates, you can enter absolute coordinates based on
the origin (0,0), or relative coordinates based on the last point specified.
8,5
–4,2
origin (0,0)
-X
-Y
X
Y