CIV 104
COMPUTER AIDED
TECHNICAL DRAWING
CHAPTER 2
Creating Basic Drawings
1
2
The Coordinate System
Every object you draw is placed in either
the world coordinate system (WCS) or
a user coordinate system (UCS).
When you create 2D geometry, data input is ultimately
passed to the software in the form of Cartesian (x,y) or
polar coordinates (distance, angle). You can either
manually enter these coordinates or infer them by
picking a point in the drawing window.
3
The Coordinate System
The Cartesian coordinate system is used to determine
points in space that are a specified distance from a set of
perpendicular axes that intersect at the origin of the system.
In the World coordinate system, the X axis represents the
horizontal direction, the Y axis represents the vertical direction
and the origin is located at 0,0. Positive X moves to the right,
positive Y moves up, and the Z axis moves in the positive direction
directly towards you, the viewer.
Note that for this course we will
only be concerned with the X & Y
coordinates since we are working
in 2D. The Z coordinate will always
be zero and need not be specified.
4
The Coordinate System
A polar coordinate is a point in the coordinate system that is
determined by a distance and an angle. The following illustration
shows a line drawn from the origin of the coordinate system with a
length of 7 units and an angle of 45 degrees.
To specify a polar coordinate,
type the distance < angle,
example 5<45, where Distance
equals the distance traveled
from the specified origin point
and Angle equals the angle
from the X axis.
5
The Coordinate System
Polar Angle
The default polar angle is measured
counterclockwise from the zero
angle position. The default zero
angle is in the East compass
direction.
6
The Coordinate System
Absolute and Relative Coordinates
When you type coordinates, they can be in the form of an absolute
or a relative coordinate.
An absolute coordinate represents a specific point in the current
coordinate system relative to the origin point (0,0). To enter an
absolute coordinate, type the values as a Cartesian coordinate
(x,y) or Polar coordinate (distance angle).
A relative coordinate is a point located from a previously selected
point. To enter a relative coordinate, select your first point, then
precede the next coordinate point with the @ symbol. For
example @5<45 would mean 5 units at 45 degrees from the last
point selected, and @3,5 would mean 3 units in the positive x
direction and 5 units in the positive y direction from the last point
selected.
7
The Coordinate System
8
Dynamic Input
9
Dynamic Input
10
Dynamic Input
11
Dynamic Input
12
13
Creating Basic Objects
14
For metric
templete
15
16
17
18
19
20
21