DRAWING WITH AUTOCAD
AutoCAD Coordinate System
AutoCAD provides different ways to specify coordinate points in your
drawing. The following features are covered in this section:
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Absolute coordinate entry
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Relative coordinate entry
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Polar coordinate entry
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Direct distance entry
-
Tracking
Absolute Coordinates
In the absolute coordinate system all points are measured from the origin
(0, 0). They are suited to situations where you know the exact X and Y
location of the point you want to place.
To enter an absolute coordinate use the format X, Y where:
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X is the distance and direction along the horizontal axis from the
origin (0, 0).
-
Y is the distance and direction along the vertical axis from the
origin (0, 0).
Relative Coordinates
Relative coordinate entries are based on the last point entered. Use a
relative coordinate when you know the location of a point in relation to
the previous point. To specify a relative coordinate, precede the
coordinate with the 'at' @ sign using the format @X, Y:
-
@ indicates a relative distance
-
X is the positive or negative distance along the X axis from the
previous position.
-
Y is the positive or negative distance along the Y axis from the
previous position.
Polar Coordinates
A combination of angle and distance input is called polar coordinate. You
use polar coordinate when you know the angle and the distance from one
point to another.
In AutoCAD angles are positive (+) when measured counter-clockwise and
negative (-) when measured clockwise.
90º
135º
45º
(+)
180º
0º
225º
315º
(-)
270º
Polar Tracking
When you are drawing and editing objects, you can use polar tracking to
display temporary alignment defined by the polar angles you specified.
Setting the polar tracking:
1- Click Drafting Setting from the Tools menu command
2- In the drafting Setting dialog box, select Polar Tracking Tab then
select Polar Tracking ON.
3- From the angle Increment Angle list, select the polar tracking
angle.
4- Under Polar Angle Measurement, specify whether polar tracking
are absolute or relative to previous segment.
5- Click OK.
Direct Distance Entry
Direct distance entry is useful when used with Ortho or Polar Tracking
option. It allows you to specify a point relative to the previous one you
entered.
Procedure:
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Move the crosshairs in the direction you want.
-
Enter a numeric distance.
Use of the line command: A line can be a single segment or a multisegment connected together. A series of lines can be open, or they can be
closed.
Steps to activate the LINE command:
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Select Line from the Draw toolbar
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Click Line from the Draw menu.
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Type Line on the command line.
Drawing Lines:
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Select Line from the Draw toolbar.
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Enter the coordinates of the starting point, in the format of X, Y.
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Enter the coordinates of the ending point.
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Continue to specify the start and end points for additional lines.
When you are ready to terminate the Line command, you can either:
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Right-click and click enter on the shortcut menu
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Press Enter key on the keyboard.
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Or press C for close if you have drawn a series segments
The UNDO Command:
If you make a mistake during the Line command, or any other process, you
can use the UNDO command to return to a point before the mistake
occurred. The REDO command allows you to reverse this operation.
You can use the undo command
from the standard toolbar, or type U at
the command line.
Drawing Tools:
Drawing with AutoCAD is based on accuracy and time saving. As far as
accuracy is concerned, AutoCAD provides you with drawing tools to help
you draw lines and point accurately. As for time saving, this is
accomplished after some years of experience using AutoCAD.
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GRID Mode: The grid is a set of dots that fill the drawing limits
you specified.
As you work you can turn Grid ON or OFF by pressing F7 or click
the GRID button on the Status bar.
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SNAP Mode: When Snap mode is ON the crosshairs is forced to
move in steps of a specific distance.
As you work you can turn Snap ON or OFF by pressing F9 or click
the Snap button on the Status bar.
Snap mode is useful for specifying precise points.
Setting Grid and Snap:
1- From the tool Menu, click Drafting Settings
2- In the Drafting Settings dialog box, select the Snap and Grid
tab, and select the Grid On (F7) to display the grid on the
screen.
3- Under Snap Type & Style, make sure the grid snap and the
rectangular snap are selected.
4- In the Grid X spacing box enter the value in units
5- To use the same value for the Y value, press Enter.
Otherwise, enter another value in the Grid Y Spacing in units.
6- Click OK.
Use the same process to setup the Snap spacing. The snap and the grid
can be set to different values.
Ortho Mode:
The Ortho mode can be activated by pressing F8 or select ORTHO from
the Status bar
. The Ortho mode is useful if you want do draw or move
objects in horizontal and vertical direction.
Object Snap (Osnap):
The Object Snap commands are drawing tools used to help you draw
accurately. Object Snaps will allow you to snap to an exact point location
of an object. When you specify an object snap, the cursor changes to a
graphic symbol. Each graphic symbol represent an Osnap option, these are
Osnap markers that appear in your drawing as you select Osnap points.
There are three ways to activate Object Snap Commands:
1- Object Snap Toolbar.
2- Osnap, from the Status bar.
3- Object Snap Dialog box, from Tool menu bar > Drafting Setting,
then Object Snap Tab.
Object Snap toolbar:
Osnap From the Status bar:
Drafting Setting Dialog box > Object Snap Tab.