Setup for Success - AutoCAD 2012 - page 84

The United States may be late coming to the party, but the U.S. federal government has made a commit-
ment to adopt SI Metric. For more information, point your browser to the National Institute of Standards
and Technology's Special Publication 814 ( http://ts.nist.gov/WeightsAndMeasures/Metric/pub814.cfm ) .
Most of the world abandoned local systems of measure generations ago. Even widely ad-
opted ones like the imperial system have mostly fallen by the wayside, just like their
driving force, the British Empire. Except, of course, in the United States, where feet,
inches, pounds, gallons, and degrees Fahrenheit still rule.
During drawing setup, you choose settings for Length units (for measuring linear objects
and distances) and Angle units (for measuring angles between nonparallel objects or
points on arcs or circles) in the Drawing Units dialog box, as shown in Figure 4-1. (I show
you how to specify these settings in the section “Setting your units,” later in this
chapter.) AutoCAD's Length unit types are as follows:
Architectural units are based in feet and inches and use fractions to represent par-
tial inches.
Decimal units are unitless — that is, they're not based on any particular real-world
unit. With decimal units, each unit in the drawing could represent an inch, a milli-
meter, a cubit (if you're into building arks in case that rainy day should come), or
any other unit of measure you deem suitable.
Engineering units are based in feet and inches and use decimals to represent par-
tial inches.
Fractional units, like decimal units, are unitless and show values as fractions
rather than decimal numbers.
Scientific units are also unitless and show values as exponents, used for drawing
really tiny or really large things. If you design molecules or galaxies, this is the unit
type for you.
AutoCAD's Angle unit types are as follows:
Decimal Degrees show angles as decimal numbers and are by far the easiest to
work with — if your type of work allows it!
Deg/Min/Sec is based on the old style of dividing a degree into minutes and
minutes into seconds. But seconds aren't fine enough to display AutoCAD's preci-
sion capabilities, so seconds can be further divided into decimals.