UNIT 5: AutoCAD Coordinate Systems Objectives: Be able to identify, describe and/or apply… AutoCAD UCS The Cartesian and Polar coordinate systems Relative and polar coordinate point entry systems to pick points in space and create drawings Assignments/Quizzes/Tests 5-1 Relative coordinates 5-2 Polar coordinates Unit 5 Test: AutoCAD Coordinate Systems

UNIT 5: AutoCAD Coordinate Systems (UCS icon) In the bottom left hand corner of the drawing area is an icon, known as the UCS icon. The icon looks like the illustration on the left and shows 3 specific bits of information. First, the icon contains a figure X and an arrow which points from left to right along the bottom of the screen. Second, the icon contains a figure Y and an arrow head which points from bottom to top along the left hand side of the screen. These first two parts of the icon indicate the position and direction of the X and Y axes. As your cursor moves over the screen area you can see the change in X and Y co-ordinates by watching the co-ordinate status area at the bottom left of the screen (X,Y,Z). X and Y co-ordinates increase in the direction indicated by the UCS icon. By implication the Z axis points straight out of the screen towards us. If you have just opened a new drawing the Z co-ordinate will appear as "0.0000" in the status bar and will not change as you move the cursor because you are only moving in the XY Plane. X Y Z NOTE: Z will remain at “0” until you are working in 3D space

UNIT 5: AutoCAD Coordinate Systems (Coordinate Systems) A good understanding of how co-ordinates work in AutoCAD is absolutely crucial if you are to make the best use of the program. Co-ordinates fall into two types, namely Cartesian and Polar. Cartesian Coordinates Despite the fancy title (named after the French philosopher and mathematician René Descartes 1596-1650), the Cartesian co-ordinate system is the standard co-ordinate system. The position of a point can be described by its distance from two axes, X and Y. This results in a simple point description using two numbers separated by a comma.

UNIT 5: AutoCAD Coordinate Systems (Coordinate Systems-Polar Coordinates) The main difference is that polar coordinates use one distance and one angle to describe the position of a point rather than the two distances in the Cartesian system. The distance and angle measurements are made relative to an origin.

UNIT 5: AutoCAD Coordinate Systems (Relative Coordinates) Points in space are created “Relative” to the last point, rather than from the origin. When entering relative coordinates at the Command Line, the @ symbol must be entered first. NOTE: Relative coordinates is assumed when using Dynamic Input with default settings NOTE: Relative coordinates work well if you know the dimensions of the object you are drawing

UNIT 5: Assignment 5-1: Relative Coordinate Systems

UNIT 5: AutoCAD Coordinate Systems (Polar Coordinates) Points in space are located based on a distance from a fixed point at a given angle. Angles are derived from the standard AutoCAD Convention that 0 degrees is to the right, or East Use the @ symbol to create geometry relative to the previous point. Use the Less Than symbol < to enter an angle

UNIT 5: Assignment 5-2: Polar Coordinate Systems Start Point 1,1 To Point B (@2<0) To Point C (@.5<45) To Point D (@3<0) To Point E (@.5<315) To Point F (@4<0) To Point G (@2.5<90) To Point H (@4.5<135) To Point I (@.25<90) To Point J (@4.5<45) To Point K (@2.5<90) To Point L (@4<180) To Point M (@.75<260) To Point N (@1.75<180) To Point O (@.75<100) To Point P (@3.6966<180) To Point Q (@5<270) To Point R (@2.5<30) To Point S (@4.5<270) To Point T (@2.5<150) Right-click select "Close"