## 2. COORDINATE SYSTEM in AutoCAD

To work in AutoCAD is necessary to know the Coordinate System

When we draw a line or any character or point, the start position will be set in relation to the coordinate system.
Coordinate system understand as a plane that can be in a position if it is a 2D drawing or more positions when it comes to drawing in 3D.

So we start from starting point in relation to the axis X and Y coordinates with the position we are in a certain place (more about that below), but remember the word origins, to the position which is currently located prior to drawing. Each time when we are positioned somewhere, our starting point is the starting point no matter where in the drawing are. The position of the origin depends on the draw in the absolute or polar coordinate system (although we may in the course of combined systems that we want)

Be sure to good learn the coordinate system,  if this does not learn then will be almost impossible to design a more complex
2D drawing about in 3D not to speak of. For 3D drawing, drawing a line in space must review the toolbar UCS and UCS II, because using them will be positioned at a starting point, surface, plane and so forth.

Layout Coordinate System

Short explanation coordinate system.

Our starting point is always in the direction East and to the first X followed by Y coordinates in direction North. (x,y).

So our starting point is the central starting point. When the Command line write some coordinates, AutoCAD will be based on this starting point (which is currently on the drawing) in relation to his position will be the starting point drawing.

Used as a guide to X axis first coordinate and Y axis for the second coordinate (except in Cartography Geodesy, there are reversed coordinates - replaced, what is the X axis in mechanical engineering and construction to the Y axis in
geodesy). It is also important to note that the axis X and Y can be so negative compared to the starting point for some sort of starting point we can enter a drawing and negative coordinates.

These negative coordinates positioned in Quadrant II and III for the X axis, and III and IV quadrant of the Y axis

Example:
If when you start drawing enter coordinate X = 50 then Autocad X axis count by 50 units in the East direction, depending on the value of Y axis, the result will be in quadrant I or IV, but if you write X = -50 then AutoCAD count 50 units
in the minus ie. in the direction of West and again depending on the value of Y axis, the result will be in quadrant II or III.

The same is true for the Y axis (Please note the Geodesy is reversed, first write the Y axis and then X (y,x)

All of this applies to enter angles in Command Line.
"COUNTER CLOCKWISE" and "CLOCKWISE" directions are in the drawing coordinate system.

The engineering and building construction uses direction "Counter Clockwise" and geodesy "Clockwise"

### What does it mean?

Means that when we draw circular arcs, and other elements depending on the direction that we will set our direction and drawing, the starting point to the end. By default AutoCAD 2007 in this direction is set in the Counter Clockwise direction, and that means the opposite of clockwise.

If you want to change this direction then the text menu, select Format => Units and select the option Clockwise. Here is set and other parameters related to the units to work in AutoCAD
Or the same parameters can be set via a dialog window in the STARTUP ADVANCE SETUP window 