Understanding the coordinate system is essential to understanding the way AutoCAD works. In AutoCAD, you can assign length and angles, as well as coordinate values, to make drawings, but to do all this, knowledge of the coordinate system is essential.

Primarily, these are two types of coordinate systems that we will use to make geometries in AutoCAD, and they are Cartesian and polar coordinates. First let's have a look at what Cartesian coordinates are.

AutoCAD follows the Cartesian coordinate system, which is a graphical method of assigning coordinates to a point in space. The simple three-dimensional space has three coordinates, namely X, Y, and Z, which are mutually perpendicular to each other, as in the following diagram. The point of intersection of the three mutually perpendicular axes is the origin, which is represented as (0,0,0):

The position of any point in a three-dimensional space can be specified using these three axes, which are represented by the X, Y, and Z axes in the preceding diagram. But for a two-dimensional space, we only need to use the X and Y axes to define the position of any point.

In a two-dimensional space, the simple (X,Y) coordinate system is used and any point in a two-dimensional space can be defined using these two coordinates only. Take the example of the following graph. Here, the origin is mentioned as (0,0), which is also the point of intersection of the X and Y axes, represented by horizontal and vertical lines, respectively:

The A (7,8) point is at 7 units from the origin along the X axis and at 8 units along the Y axis. Similarly, the B (-6,3) point is at 6 units along the negative side of the X axis and at 3 units along the positive side of the Y axis. In the case of the C (4,-5) point, the distance from the positive side of the X axis is 4 units, and its distance along the negative side of the Y axis is 5 units.

The X axis points to the right of the origin are positive and the points to the left of the origin are negative. Similarly, on the Y axis, the points on top of the origin are positive and the points below the origin are negative.

Using polar coordinates, we can also represent points in a two-dimensional space. In this case, one polar distance and an angle with respect to the X axis are required instead of the X and Y coordinate values. To understand this clearly, have a look at the following graph:

In this case, the B point is represented by (8<30), where 8 is the distance between the A and B points. Here, A is the origin and 30 is the angle between line AB and the positive X axis in an anticlockwise direction.

This type of coordinate representation, where a point in space is represented by an angle with respect to the positive X axis and the distance from the origin, is known as a polar coordinate system.

Throughout this book, we will use both methods of coordinates to make our drawing. Drawings in AutoCAD are not essentially made only with coordinate values. For most of the cases, we use a general approach of direct distance entry and we use coordinates only in specific situations.

In the next section, we will start making our first drawing with the Line command using direct distance entry as well as different coordinate values.

You can select the Line command from the command bar, using its command alias, or you can also select the command from the ribbon panel. The Line command will make a straight-line segment of any specified length. This is the most basic of the draw tools and one of the most frequently used ones in the drawing workflow.

The Line command is in the Draw panel of the Home tab. To start the command, you need to left-click on its icon once or you can use its command alias, L. In this case, let's start the Line command from the ribbon panel:

Once your command is active, you will notice that the cursor will change into a point selection cursor that looks like two perpendicular intersecting lines and the command line will also show the name of the command, along with the prompt, as shown in the following screenshot:

Now, AutoCAD is ready for your input and you can start making the line. To do that, perform the following steps:

1. Click on any point in the drawing area and the line will start from that point. Move your cursor and you will notice that the line will follow the movement of the cursor and it will stretch with the cursor, too. This line is also called a rubber bending line, which follows your cursor.
2. Click on a second point in the drawing area and the fixed-length segment of the line will be made and the rubber bending line will again follow from the last point where you clicked. Repeat the process to make additional lines, and when you are done making the geometry, press the Enter or Esc key to exit the command.

This is the general workflow for making a random curve in AutoCAD but, as you have noticed, this method lacks precision as the distance was not specified for the line. To make drawings with precise distances, you need to use the direct distance entry method, which is explained in the next section.

In AutoCAD, direct distance entry is the most obvious way of making lines of precise length. This method is fairly easy, too. To explain this method, I will make a rectangle with a length of 7 units and a width of 5 units using the direct distance entry method and a line tool, as in the following example:

1. Select the Line command from the Draw panel of the Home tab, as in figure 2.4, or type L and press Enter to start the command using its command alias.
2. The command line will prompt you to specify the first point, as in figure 2.5. Click anywhere in the drawing area to add the first point of the line and let go of your mouse cursor and move your mouse elsewhere. The rubber bending line will be formed starting from the first point.
3. Move your cursor in a horizontal direction and type a distance value. In this case, type 7 and press the Enter key again.
4. The line will be formed in a horizontal direction with a length of 7 units.
5. Now, move your cursor in an upward direction and again type another value. In this case, type 5 and press Enter. Another line in a vertical direction with a length of 5 units will be formed.

6. Move your cursor again to the left, type 7, and press Enter again to make another horizontal line.
7. Move your cursor down, type 5, and press Enter again. The line will return back to the starting point.
8. The command will still continue and you will have a rubber bending effect of the line. Press the Enter or Esc key to exit from the Line command.

Once you are done with all the previous steps, you will have a rectangle that looks like the following screenshot. In this rectangle, the length is 7 units and the width, or height, is 5 units:

This direct distance method is generally used to make drawings in AutoCAD and, as you have noticed, it allows you to make precise drawings as well. A similar workflow can also be used to make other geometries.

There are other methods of making drawings in AutoCAD and we will discuss these in the next section.

Let’s take the example of this triangle shown here. In this case, all three coordinates of this triangle are labeled as point A, B, and C:

We will make this triangle in the following example using the Line command, but instead of direct distances, we will use coordinate values:

1. Select the Line tool from the Draw panel or use its command alias, L, to start the command.
2. The command line will prompt you to specify the first point for the line, as in figure 2.5. Type 0,0 for the first coordinate point, which is also the A point of the triangle, and press Enter.
3. Now, we need to specify the coordinates of the second point, B. Type 10,0 and press Enter again. The cursor will move to the B point of the triangle.
4. Once again, we need to specify the coordinates of the next point, C. So, type 14,7 and press Enter.
5. Now, our cursor is at the C point and you can simply type 0,0 and press Enter to return to the first point, which is the origin. To exit the command, press the Enter or Esc key once.

As you have noticed, we only required the coordinates to make this triangle, but the coordinates are rarely used for making drawings and, in most cases, the length and angle values are predominantly used. In real-world drawings too, we will use direct distance entry primarily, but there will be a few instances where coordinates will also be used to make drawings.

In the next example, we will learn how to make a simple drawing using the polar coordinate system.

Using polar coordinates, you can add distance and angle values directly to the command line and they need not be entered separately. To explain this, I will use the following diagram:

In this case, we need to draw a line that is inclined at an angle of 36 degrees with respect to the positive side of the X axis and has a length of 6 units. The following is the workflow for making this line:

1. Type L and press Enter to start the line command.
2. Type 0,0 and press Enter to start the line from the origin.
3. Type 6<36 in the command line and press Enter.
4. The line with a length of 6 units and a 36 degree angle with respect to the X axis will be made.

In this case, we started the line from the origin, and the distance from point A to point B is 6 units and the angle this line makes with respect to the positive side of the X axis is 36 degrees. So, you can add both of these values in the polar coordinate to form a DIS<ANG format, where DIS is the distance and ANG is the angle.

If, however, you start the line not from the origin, but from a random point in the drawing area and still want the same result, then you need to add an @ sign before the polar coordinates. This method is known as the relative coordinate system, which is explained next.

To explain the relative coordinate system, I will once again use the same diagram that we used in the previous section, but in this case, the line will not start from the origin. Rather, we will start it randomly from any point in the drawing area, as in the following diagram:

So, the same line with a length of 6 units that is not starting from the origin and has an inclined angle of 36 degrees can be made using the following workflow:

1. Type L and press Enter to start the line command.
2. Click on any point in the drawing area to start the line.
3. Type @6<36 in the command line and press Enter.
4. The line with a length of 6 units and a 36 degree angle with respect to the X axis will be made.

This @ sign represents the relative coordinate system, which allowed us to make a line from a point that is not on the origin. Here is another example of relative coordinates.

As explained in the previous example, relative coordinates are helpful when you are making a drawing from a point that isn't the absolute origin and still want to use the selected point as a reference for adding the coordinates. In this example, I will create the following triangle using relative coordinates:

Here, you can start the drawing at point A, which is not on the origin, and then progressively make your drawing by entering distances. Instead of direct distances, however, we will use relative coordinates to make this triangle in the following example:

1. Start by selecting the Line command and then click on a point in the drawing area, making sure that the point is not at the origin. Let’s call it point A. As the A point is chosen randomly, we can’t specify an exact value of the (X,Y) coordinate for the B point with respect to the A point. So, in this case, we can use relative coordinates to specify a coordinate value of the B point with respect to the A point. Relative coordinates assume that the last point you clicked or selected is the origin and then make all measurements from that last point as if that point were the origin.
2. So, if point A were the origin, then point B should be 8,0, with respect to point A. To make the AB horizontal line, type @8,0 and press Enter. The line will end up at point B, as in figure 2.10. Note the @ sign before the coordinate value. This @ sign is added to indicate that the next coordinates are "relative" with respect to the point that we previously clicked, which is the A point, in this case, and it will assume the A point as the origin instead of the absolute origin of the drawing.
3. Once you have reached point B, don’t exit the line command, but type @0,6 and press Enter. You will notice that AutoCAD will reach point C, as in figure 2.10, and in this case, the B point will also be treated as the origin and the coordinate value of the C point with respect to the B point is 0,6, which is shown with the @ sign.
4. You can complete the triangle by clicking again on the A point and then pressing Enter to exit the line command.

So, now that we have seen different methods of making the drawing in AutoCAD, let’s use a combination of these methods to make a simple drawing.

So far, we have used different coordinate systems to make a drawing, but it is generally not the ideal way of making drawings in AutoCAD. Generally, we would use direct distances and angles instead. In this section, we will learn how to use this method to make drawings. To explain this example, I will use this triangle:

In this drawing, there is no coordinate information provided and we will use only the dimension values, such as the length and angle, provided here to make it. We will make this triangle performing the following steps:

1. Open a blank drawing and start the line command by clicking on the Line tool in the Draw panel, or by using the L command.
2. Click at a point in the drawing area to start the rubber bending line and move your cursor toward the right side. Type 10 in the command line and press Enter.
3. Press Enter again to exit the command.

4. Click again at the starting point of the line (point A) and type <30, and then press Enter. Notice the < angle sign before 30. In this case, entering the angle sign before 30 will tell AutoCAD to take the numeric value as an angle and not a distance. Once you press Enter, you will notice that the line will be locked at an angle of 30 degrees with respect to the positive side of the X axis.
5. Move your cursor in the direction of the 30 degrees line and type 14, and then press Enter again. This will make a line at an angle of 30 degrees with a length of 14 units.
6. Click on the B point, as in the preceding diagram, and press Enter again to exit the command.

In this case, you saw that geometry can also be made by entering values of the distance and angle directly in the command line. This method is relatively easy when compared to the coordinate entry method. This is also the most common way of making drawings in AutoCAD. There are also some status bar modes that help you to generate references that can be used to make precise drawings. These modes are Dynamic Input, ortho, and polar tracking, and we will discuss them in the next section.

The status bar modes help you make precise drawings in AutoCAD. The tools in the status bar can be toggled on and off by clicking on their icons or by using their function keys. Not all status bar icons are visible by default and you can toggle the visibility of the icons as per your requirements:

To change the visibility of icons in the status bar, click on the customization icon, shown as three dashes on the far-right side of the status bar, and click on the name of the icon that you want to show on the status bar. When visible, a checkmark will show next to the icon's name. In the following screenshot, you can see Dynamic Input and other status bar toggles checked in the customization menu:

In this section, we will discuss some of the most basic status bar toggles that we need in order to render drawings precisely.

Dynamic Input allows you to enter the distances, angles, and other values right inside a drawing with a visual reference. Using the Dynamic Input tool, you can bypass the command line and enter the details directly in the drawing.

To explain the Dynamic Input tool, I will again use the drawing of an inclined line shown in the following diagram:

Here, we will make our inclined line with a length of 6 units and an angle of 36 degrees, with respect to the positive side of the X axis, performing the following steps:

1. Click on the Dynamic Input icon in the status bar and it will turn blue when active. You can also type DYNMODE, then press Enter, and then type 3 and press Enter again to activate the Dynamic Input mode. The default value of the DYNMODE system variable is -3. You can also activate or deactivate the Dynamic Input mode using the F12 function key:

2. When the Dynamic Input mode is active, select the Line command and you will now notice a tooltip on the cursor with the value of the X and Y coordinates of the point, as in the following screenshot:

3. Now, click at a point in the drawing area and your tooltip on the cursor will change to represent a length and an angle field, as in the following screenshot:

4. Here, the length field is active and ready for your input. Type the length of the line in this field and press the Tab key on your keyboard.
5. The line will be locked at a length of 6 units and a lock sign will also appear next to the length field of the tooltip. Also, the angle field will be highlighted. Now, enter the angle value without any angle sign, which in this case will be 36, and press Enter.

We now have our required line with a length of 6 inclined to an angle of 36 degrees, with respect to the X axis.

So, as you have noticed, this is a quick and effective way of making geometries in a drawing, which you can use to bypass the coordinate or direct distance entry methods. If, for any reason, you don't want to use this Dynamic Input tool, then click on the Dynamic Input icon again on the status bar to deactivate it.

So, now you know that Dynamic Input makes it easy to add distances and angles, let's move on to learning about another status bar mode called ortho mode, which makes rendering horizontal and vertical lines a breeze. We will discuss this status bar mode in the next section.

So far, we have used the line command to make geometries in arbitrary directions. But if you want to restrict the direction of your lines to horizontal and vertical directions, then you can use ortho mode. Ortho mode restricts the movement of the cursor to a horizontal or vertical direction only, so with ortho mode active, you will be able to make lines only in a horizontal or vertical direction. To activate ortho mode, you can use the following workflow:

1. Click on the ortho mode icon in the status bar, as in the following screenshot, or press the F8 function key on your keyboard:

2. Select the Line tool from the Draw panel or use its command, L, and click on a point in the drawing area.
3. Now, move your cursor around and you will see that the line will remain restricted to a horizontal or vertical direction, depending on the movement of your cursor.

You can click on different points to make the geometry but the lines will always remain horizontal or vertical. To deactivate ortho mode, simply click on its icon in the status bar again or press the F8 function key on your keyboard. Just like ortho mode, there is another mode in the status bar that lets you make lines on any angle you specify. This mode is called polar tracking and we will discuss it in the next section.

Polar tracking allows you to make geometries at any angle you want. To activate polar tracking, click on its icon in the status bar, as in the following screenshot. You can also activate polar tracking by pressing the F10 function key on your keyboard:

When polar tracking is active, it will automatically deactivate ortho mode.

1. Start the Line command again by selecting its command, L
2. Click at a point in the drawing area and move your cursor in the horizontal or vertical direction.
3. You will notice a green tracking vector when the cursor is horizontal or vertical and this will help you to restrict the line to a horizontal and vertical direction:

But this is not all. In this case, you can assign a different angle to polar tracking mode and it will start restricting your lines to those angles.

1. To change the angle of polar tracking, click on the small arrow right beside the polar tracking icon.
2. When the angle menu shows up select the angle that you want to choose.
3. By default, 90 and its multiples will be selected, but we will change this to 30 and its multiples, as shown in the following screenshot:

4. You can select any other angle value as well, if you want to, from the list.

After making your selection, move your cursor again to the drawing area and now you will find a green tracking vector after an interval of every 30 degrees or at every angle that is a multiple of 30 degrees as shown in the following figure:

These status bar options allow you to make geometries. To make drawings, we will use a combination of these status bar tools as and when needed.

So, now that we know the methods for making simple line drawings with precision in AutoCAD, we will move on to learning about other geometries, such as circles, arcs, and polygons.

You can select the Circle command from the Draw panel in the Home tab, or you can also use its command, C. When you click the Circle flyout, you will find six different methods for making a circle in AutoCAD:

We will talk about all of these methods in the following sections.

The first option in the Circle flyout will let you make a circle with center and radius values. The following is the workflow for making a circle using a center and radius:

1. Select the first option from the Circle flyout. The command line will now prompt you to specify the center of the circle:

2. Click on any point in the drawing area and this will be selected as the center of the circle.
3. Now, the command line will prompt you to specify the radius of the circle. Type the radius value in the command line and press Enter to make the circle, or you can also move your cursor in the drawing area and click on a point to make your circle.
4. The circle will be made with a specified radius and center point.

Let’s repeat the preceding example again to make a circle with a diameter value this time:

1. Type C and press Enter to start the Circle command, or use the Circle tool from the Circle flyout.
2. Click on a point to specify the radius of the circle and then the command line will prompt you to specify its radius:

3. Don’t add the radius value at this point. In the command line, you will also see that after or, Diameter is highlighted with D in uppercase. Using this option, you can convert the radius input of the command line to the diameter. So, instead of radius, type D and then press Enter.

4. The command line will change again and this time it will prompt you to specify the diameter instead of the radius. You can also click on the highlighted Diameter option in the command line to select it instead of typing D and pressing the Enter key:

5. Now, type the value of the diameter in the command line and press Enter and your circle will be rendered with the required diameter. In the Circle flyout, the second option, Center, Diameter, will also let you make a circle with a center and diameter.

So, these two methods are nearly identical, the only difference being the radius or diameter value that you need to make the circle. The methods shown in the next section are, however, completely different and you don't even need the radius or diameter value for them.

The next circle option, 2-Point, requires you to specify two points for making the circle. For this, I will use the triangle shown here. Here, AB is 10 units and AC is 8 units in length:

In the following example, I will make a 2-point circle on the AC line of our sample triangle:

1. Select the 2-Point option from the Circle flyout.
2. Click on the A point, then click on the C point, and you will end up with a circle that looks like the one in the following diagram.
3. In this case, the AC line is on the diameter of the circle and the length of the AC line will be equal to the circle's diameter:

The next example, a 3-Point circle, will need three points to make the circle:

1. Select the 3-Point circle command from the Circle flyout and then click on the A point, then the B point, and finally, on the C point of our example triangle.
2. The circle will be made by connecting all three points of the triangle, as in the following diagram:

The next set of options in the Circle flyout will let you make the circle with the tangent and radius as references. We will discuss this next.

The next example will require you to specify two geometries on which the circle will be tangent and then the radius of the circle:

1. Select the Tan, Tan, Radius circle option from the flyout.
2. Click anywhere on the AB line and then click anywhere on the AC line. Now, the command line will prompt you to select the radius of the circle, as in the following screenshot.
3. Type 2 and press Enter and you will have your circle that is at a tangent to the AB and AC lines. The radius of the circle will be 2 units, as demonstrated in the following diagram:

In the last circle option, Tan, Tan, Tan, you need to only specify three geometries on which the circle will be tangent:

1. Select the Tan, Tan, Tan circle tool from the Circle flyout.
2. Click on the AB line, then click on the BC line, and finally, click on the AC line.

3. You will get a circle that is tangent to all three lines and it will look like this:

So, in this way, you can make circles using different methods and the selection of the method depends on the dimensions provided and the type of geometry you are required to make. In the next section, we will explore the arc tool, which is basically a part of the circle, but the workflow of making an arc is very different from that of a circle.