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Up to this point we have been referring to our distances as units. Now are these units inches, millimeters or feet? Let's take a second and discuss how we can assign a real world unit of measurement to our drawing. I am going to start by creating a line segment. Let me come up and click my Line icon and then I am going to come out into my Model space area and I am going to pick one point on my screen and I am just going to pull at some arbitrary angle and I am going to type in a distance of 1 and hit Enter. Now that I am done with the command I am going to hit my Escape key to cancel out. I just created a line segment that's 1 unit long.
Now what does that unit represent. Well that unit represents whatever unit of measurement I want it to represent. You see when we create a drawing in AutoCAD what would be the most convenient unit of measurement for me to use to create my drawing and then that's what we set our drawing to. Let me give you an example. I am going to open a drawing. I am going to come up and click my Open icon and we are going to go one of the Exercise Files folder and we are going to Chapter 4, Defining Our Units, and then I am going to grab this first drawing, Units basketball, and we will open it up on screen.
Now this is a drawing of a basketball. Now the typical diameter of an NBA Basketball is 9.39 inches, so when I created this drawing I asked myself what would be the most convenient unit of measurement for me to use to produce this drawing. Well if one unit equaled 1 inch that would be very convenient because then I can just draw a circle with a diameter of 9.39. So in this drawing every unit equals 1 inch. Let me open another drawing. I am going to come up to my Open icon and click. Let's open up under the Chapter 4 folder.
We will grab this second drawing. Units basketball court and click Open. Now when I created this drawing I asked myself the same question. What would be the most convenient unit of measurement for me to use to create this drawing? Well if 1 unit equaled 1 foot that would be very convenient because then as I drew my line in this direction I can just type in 94. If I drew my line in this direction, I can just type in 50 so in this drawing every unit equals 1 foot. Now there are industry standard conventions. I don't want you to think that I get up every morning and I just draft something in millimeters and draft something in inches.
If you are a civil engineer or a surveyor your drawings will be set such that 1 unit equals 1 foot. That is an industry standard. If you are an architect your drawing will always be set such that 1 unit equals 1 inch. If you draft using metric units, your units will probably be set to millimeters or centimeters. Let me close these drawing and I click the x to close this drawing. We will click the x to close this one and we return to our single unit line. Now where can I apply my unit of measure to this drawing? I can do that through the Format pulldown so I am going to come up to the Formats menu and then click and then I am going to come down and select Units.
This will bring up my Units dialog box on the screen. Right here in the Insertion scale area this is where I am declaring to the world my unit of measure that I am using for this drawing. If I click the dropdown, we can see that we have several choices available. More often than not we will be using the units at the top of the list, unless you are building the Death Star or something quite large you probably won't be touching the units now at the bottom. For right now I am going to set this to Inches. This means that every unit in my drawing represents 1 inch. Also notice that this is in the Insertion scale area and it says Units to scale in certain content.
That means if my buddy next door is doing a metric drawing and he happens to set his units to millimeters if I was to insert his drawing into my drawing AutoCAD will automatically do the units conversion such that his geometry comes in at the appropriate size. Let's look at the top of the dialog box. Up here I have got a Length area and an Angle area. This controls how AutoCAD lists our geometry. If I was to ask AutoCAD how long is this line or how long is this arc, AutoCAD will tell me the length using decimal inches to a precision of 4 decimal spaces.
Now we can list our geometry more accurate if we wish. We can go from the even integer all the way up to 8 spaces to the right of the decimal. Likewise we don't have to use the decimal type for our length. If I click the dropdown, I have several other choices. The two that are used most often are Architectural and Decimal. If you are a mechanical drafter or a civil engineer or surveyor, you will be using the Decimal type because you will want your distances given in decimal values. If you are an architect you will set this to Architectural and then your distances will be given using fractional values.
So let me set this back to Decimal. We will try it out. As it's set-up right now if I was to list my line segment, AutoCAD will give me the length of the line in decimal inches to four spaces to the right of the Decimal. Let me click OK to get out of the dialog and let's try that. To list my line I am going to go to my Tools pulldown and I am going to select Inquiry, List. I can use the List command to query my geometry so AutoCAD is asking me to select objects. I am going to come down and click on this entity and then I am going to right-click to finish the selection and in my AutoCAD Text Window I get a whole bunch of information that really means nothing to us right now except for this area right here.
Notice that I am getting the length of the line in decimal. It happens to be 1 inch long and the distance is given to me using 4 decimal spaces. Let me close my Text Window. Let's go back into the Units dialog. I am going to go back to Format, Units. In addition to controlling how AutoCAD lists our length, we can also control how AutoCAD lists our angles. Currently it's set to decimal degrees. If I click the dropdown I also have the choice of Degrees, Minutes, Seconds, Grads, Radians or Surveyor's Units. Let me leave this at Decimal Degrees.
I can also control the precision of how AutoCAD lists my angles. Let me click the dropdown. Everywhere from even integer all the way down to 8 spaces to the right of the decimal. Let me click to get out. As we leave this dialog box we can remember that for this drawing every 1 unit represents 1 inch. AutoCAD by nature is flexible enough to allow you to draft using whatever unit of measurement is most convenient for you and whether you like drafting in inches, millimeters, feet or something else entirely, you can always find whatever you need in the Units dialog box.
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