AutoCAD® 2011 & AutoCAD LT® 2011 Bible

Chapter 4. Specifying Coordinates

IN THIS CHAPTER

• Working with absolute, relative, and polar coordinates

• Using direct distance entry, orthogonal mode, and polar tracking

• Using snap settings

• Working with object snaps

• Locating points

Specifying points in a drawing is one of the most fundamental tasks you do in AutoCAD and AutoCAD LT. Unless you know how to specify a point, you can't draw anything real, whether a house or a gasket. Most objects you draw have a specific size, and you need to specify that information. You draw lines, arcs, and circles by specifying the coordinates of points on the screen. As with most tasks, AutoCAD and AutoCAD LT offer many ways to accomplish this.

Understanding the X,Y Coordinate System

AutoCAD and AutoCAD LT work the same way as the graphs with X and Y axes that you plotted in high school. Look at the User Coordinate System (UCS) icon shown in Figure 4.1.

Note

The UCS icon can take on different appearances. See Chapter 8 for details. For information on the UCS icon in 3D drawing and 3D coordinates, see Chapter 21.

The X arrow points along the X axis in the positive direction. This means that as you go in the direction of the arrow, the X coordinates increase. The Y arrow points along the Y axis in the positive direction. Using this system, every 2D point on the screen can be specified by using X and Y coordinates. This is called a Cartesian coordinate system. The universal convention is to place the X coordinate first, and then a comma (but no space), and then ...