1. Coordinate Systems Cartesian, Relative and Polar
Engineering Design Technology
Sacramento City College
Coordinate Systems

2. Point Entry Mode
Each of the point entry methods uses the Cartesian coordinate system.
The Cartesian coordinate system is based on selecting distances from three intersecting axes, X, Y, and Z.
A location is defined by its distance in x,y from the origin point.
Most of our work will be in 2D not 3D.
Coordinate Systems

3. The Cartesian Coordinate System
The Origin divides the coordinate system into four quadrants.
Points are located in relation to the origin.
The Origin is point 0,0 and is the location where the X and Y axes cross.
For AutoCAD, the origin is the lower-left of your drawing.
Coordinate Systems

4. Quadrant 1
Origin (0,0)
Coordinate Systems

5. The Cartesian Coordinate System
Quadrant #2
-x, +y
Quadrant #1
+x, +y
Origin (0,0)
Quadrant #3
-x, -y
Quadrant #4
+x, -y
Coordinate Systems

6. Using Absolute Coordinates
Points are measured from the origin.
A point [4,2] is
4 units in the X direction.
2 units in the Y direction.
from the origin.
The coordinate display on the lower left corner of the screen shows the location of the cursor at any time.
Coordinate Systems

7. Using Absolute Coordinates
You can draw lines by typing in the coordinates of the line.
Command: L or LINE
Specify first point: 4,2
Specify next point or [Undo]: 7,2
Specify next point or [Undo]: 7,6
Specify next point or [Undo]: 4,6
Specify next point or [Undo]: 4,2
Specify next point or [Undo]: [Enter]
Command:
Coordinate Systems

8. Using Relative Coordinates
Relative coordinates are located from the previous position, rather than from the origin.
The symbol must precede each entry.
Coordinate Systems

9. Using Relative Coordinates
Command:
Specify first point: 2,2
Specify next point or
Specify next point or
Specify next point or
Specify next point or
Specify next point or
Specify next point or [Undo]: [Enter]
Coordinate Systems

10. Using Polar Coordinates
A point located using polar coordinates is based on
the distance from a fixed point
at a given angle (< 45)
Procedure:
Enter the distance
then
Enter the angle
Example: @6<45
Coordinate Systems

11. Using Polar Coordinates
The angular values used for polar coordinates are:
0 = east (or to the right)
90 = North (or up)
180 = West (or to the left)
270 = South (or down).
Coordinate Systems

12. Using Polar Coordinates
@4<45 means
Measure from the previous point
A distance of 4
At an angle of 45 degrees from 0 degrees.
Coordinate Systems

13. The Coordinate Display
Coordinate Systems

14. The Coordinate Display
The coordinate display shows the current cursor location.
Turn the cursor tracking display on and off with the [F6] key.
Coordinate Systems

15. The COORDS Variable
The COORDS variable lets you choose how the coordinates will be displayed.
0 = the coordinate display is static. Coordinates are displayed only when points are selected.
1 = the coordinate display is dynamic.
2 = the coordinate display is in polar mode showing length at an angle.
Coordinate Systems