Chapter 4 CAD Commands and Functions 103
located in the two left quadrants have negative
X coordinate values and positive or negative Y
coordinate values. Specifying point locations
with absolute coordinates is the most basic way
to locate points.
Coordinates for point locations can also be
entered as relative coordinates, Figure 4-1B.
Relative coordinates defi a location from a fine
previous point. The @ symbol is typically used
to designate a relative coordinate entry. For
example, suppose you have located the first fi
point of a line at the coordinate (3,3) shown in
Figure 4-1B. Entering the relative coordinate
@4,5 would place the endpoint of the line four
units to the right and fi ve units above the pre-
vious point at the coordinate (7,8).
When it is necessary to locate points relative
to given points at specific angles (such as the fi
endpoints of an inclined line), polar coordinates
are useful. Polar coordinates are relative coor-
dinates that define a location at a given distance fi
and angle from a fi xed point (most typically a fi
previous point). See Figure 4-1C. The coordinate
entry format @distanceangle is normally used
to specify polar coordinates. In this type of
coordinate entry, angular values are typically
measured from 0° horizontal. For example, in
Figure 4-1C, after locating the first point of a fi
line at the coordinate (1,1), entering the polar
coordinate @1430 locates the endpoint 14 units
away from the fi rst point at an angle of 30° fi coun-
terclockwise in the XY plane.
Figure 4-1. Methods of two-dimensional coordinate entry in the Cartesian coordinate system. A—Absolute
coordinates are located in relation to the origin along the horizontal and vertical axes (XY axes). Coordinates can
have positive or negative values and are designated as (X,Y). ( ( B—Relative coordinates are located in relation to a
previous point. C—Polar coordinates are located by specifying a distance and angle relative to a given point.
(2,4)
(–6,6)
(4,–4)
(–3,–7)
(+X,+Y)
(+X,–Y)
(1,1)
(–X,–Y)
(–X,+Y)
Origin (0,0)
Absolute Coordinates
A
Relative Coordinates
B
Polar Coordinates
C
X axis
X axis
4 units
5 units
@4,5
(7,8)
@1430
(3,3)
Y axis Y axis