How to Use Coordinate Input
Quick answer: Every drawing has a fixed World Coordinate System (WCS), and you can also define your own User Coordinate Systems (UCS) anywhere within it. You can type points and distances in three formats, Cartesian (x,y,z), cylindrical (R<alpha,z), or spherical (R<alpha<beta), and prefix an entry with @ for relative coordinates or * for absolute WCS coordinates.
WCS and UCS
A drawing’s World Coordinate System is fixed. A User Coordinate System is one you define yourself, it can sit anywhere within the WCS and be oriented in any direction.
The Three Coordinate Input Formats
- Cartesian coordinates:
x,y,z - Cylindrical coordinates:
R<alpha,z - Spherical coordinates:
R<alpha<beta
Relative Coordinates
Typing @ in front of an entry calculates the coordinates relative to the previous point, rather than from the origin.
This also happens automatically: while Dynamic Dimensions are active, typing a value into the Length field and adding a comma copies that value straight to the Command line with an @ placed in front of it, ready to specify the next point relative to the last one.
Absolute Coordinates
If a UCS is currently active, typing * in front of an entry refers to absolute WCS coordinates instead of the active UCS’s own. For example, *0,0 refers to the WCS origin specifically, not the origin of whatever UCS you’re currently working in.
Cartesian Coordinates in Detail
Three perpendicular axes, x, y, and z, all originate at the coordinate system’s origin point. The x and y axes define a horizontal plane; the x-z and y-z axis pairs each define a vertical plane. A point’s Cartesian coordinates are its distances from the yz-, xz-, and xy-planes.
- Type the x, y, and z coordinates separated by commas for absolute Cartesian coordinates.
- Omit the z-coordinate, and the point is placed in the xy-plane (Z = 0).
- Prefix the entry with
@(@x,y) for relative Cartesian coordinates, calculated from the previous point.
Cylindrical Coordinates in Detail
Format: R<alpha,z
R: distance to the origin in the xy-plane<alpha: the angle between R and the x-axis, positive angles measured counterclockwisez: height above the xy-plane
Omit the z-coordinate, and what you’re entering is technically called a polar coordinate rather than a cylindrical one. As with Cartesian coordinates, prefix the entry with @ to calculate it relative to the previous point.
Spherical Coordinates in Detail
Format: R<alpha<beta
R: distance from the origin<alpha: the angle in the xy-plane, positive angles measured counterclockwise<beta: the angle measured from the xy-plane itself, positive angles measured counterclockwise, above the xy-plane
Frequently Asked Questions
What’s the difference between cylindrical and polar coordinates? They’re the same format, but a cylindrical coordinate includes a z-height above the xy-plane; omit the z-coordinate, and it’s referred to as a polar coordinate instead.
How do I enter a point relative to the last one I placed? Prefix the entry with @, for example @x,y for relative Cartesian coordinates.
How do I enter absolute WCS coordinates while working in a custom UCS? Prefix the entry with *. For example, *0,0 refers to the WCS origin, not the active UCS’s own origin.
What happens if I leave out the z-coordinate when entering Cartesian coordinates? The point gets placed in the xy-plane, with Z automatically set to 0.