Читать книгу AutoCAD For Dummies онлайн

88 страница из 139

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 60 minutes and minutes into 60 seconds. Seconds aren’t fine enough to display AutoCAD’s precision capabilities, though, so seconds can be further divided into decimals. There is no degree symbol on a standard keyboard, so AutoCAD uses the lowercase letter d. An example would be 45d30′10.7249″. One nautical mile (6,076 feet) is approximately 1 minute of arc of longitude on the equator. David Letterman once said that the equator is so long that it would reach once around the world.

 Grads and Radians are mathematically beautiful (so we’re told) but are not widely used in drafting. Apparently, the French artillery uses grads but as long as we’re friends with them we shouldn’t have to worry. Some of AutoCAD’s built-in programming language uses radians for angles. There are 400 grads, and 2*pi (6.2831…) radians, in a circle.