Units and Unit Formats

Before you start to draw, you decide on the units of measurement to be used in the drawing, and set the format, precision, and other conventions to be used in coordinates and distances.

 Before you start to draw, you must decide what one drawing unit represents based on what you plan to draw. You can convert a drawing between systems of measurement by scaling it.

 Every object you create is measured in drawing units. Before you start to draw, you must decide what one drawing unit will represent based on what you plan to draw. Then you create your drawing at actual size with that convention. For example, a distance of one drawing unit typically represents one millimeter, one centimeter, one inch, or one foot in real-world units.

Convert Drawing Units

If you start a drawing in one system of measurement (imperial or metric) and then want to switch to the other system, use SCALE to scale the model geometry by the appropriate conversion factor to obtain correct distances and dimensions.

For example, to convert a drawing created in inches to centimeters, you scale the model geometry by a factor of 2.54. To convert from centimeters to inches, the scale factor is 1/2.54 or about 0.3937.

To set the units format and precision

• Click the Application button, and click Drawing -> Units.
• In the Drawing Units dialog box, under Length, select a unit format and precision. Click OK. The Sample Output area shows an example of the unit format at the current precision.

To convert a drawing from inches to centimeters

• Click Home tab Modify panel -> Scale.
• At the Select Objects prompt, enter all. All objects in the drawing are selected for scaling.
• Enter a base point of *0,0. Scaling will be relative to the world coordinate system origin and the location of the drawing origin will remain at the WCS origin.
• Enter a scale factor of 2.54 (there are 2.54 centimeters per inch). All objects in the drawing are now 2.54 times larger, corresponding to the equivalent distance in centimeters.

Linear Unit Conventions

Before you start to draw, you set the format and the number of decimal places to be used when you enter and display linear units.

You can choose from several common conventions to represent the display style and the precision of distances and coordinates. Depending on what you specify, you can enter and display in decimal format, fractional format, or other notation. These settings affect

• The Properties palette
• Dynamic input
• The LIST command
• The ID command
• The coordinate display on the status bar
• Several dialog boxes that display coordinates

You can set the unit type and precision in the Drawing Units dialog box, the Quick Setup wizard, or the Advanced Setup wizard.

Rounding and Precision – When you specify the display precision of units, the values for coordinates and distances are rounded off. However, the internal precision of coordinates and distances is always maintained regardless of the display precision.

For example, if you set the display precision of decimal-format units to 1 (or 0.0), the display of coordinates is rounded to one place after the decimal point. Thus, the coordinates 0.000,1.375 are displayed as 0.0,1.4, but the internal precision is still maintained.

Imperial Architectural Format – In architectural format, to enter feet and inches, indicate feet using the prime symbol (‘), for example, 72’3. You don’t need to enter quotation marks (“) to specify inches. The units format for creating and listing objects, measuring distances, and displaying coordinate locations is separate from the dimension units setting used in creating dimension values.

Angular Unit Conventions

Angle conventions include the position of angle 0 and the direction of measurement: clockwise or counterclockwise. You also set the format and the number of decimal places.

You can choose from several common conventions to represent angles in a drawing. You can specify that positive values of angles are measured either clockwise or counterclockwise, and angle 0 can be set to any direction (usually East or North). You can enter angles using grads, radians, or surveyor’s units or using degrees, minutes, and seconds.

Surveyor’s Angles – If you use surveyor’s angles when specifying polar coordinates, indicate whether the surveyor’s angles are in the north, south, east, or west direction. For example, to enter a coordinate relative to the current coordinate for a property line that is 72 feet, 8 inches long with a bearing of 45 degrees north, 20 minutes, 6 seconds east, enter

@72’8″<n45d20’6″e

To set the angle format and precision

• Click the Application button, and click Drawing Utilities -> Units.
• In the Drawing Units dialog box, under Angle, select an angle type and precision. The Sample Output area shows an example of the angle type at the current precision.
• Select Direction to specify an angle direction. The angle direction controls the point from which angles are measured and the direction in which they’re measured. The default starting angle, 0 degrees, is toward 3 o’clock (or east), and positive angle measurement is counterclockwise.
• Select the options you want to use.
• Click OK to close each dialog box.