Units and Scale are two of the most important settings in an AutoCAD drawing. You can prevent any number of problems by ALWAYS setting your units and scale before you begin work on a drawing. If you have already begun work on a site design and are running into issues resulting from your Units and Scale settings being off, you can address the problem by verifying and correcting your units and scale.
Having scaling issues with your blocks? See our Blocks Coming In at the Wrong Scale article.
Verify Your Units Setting
A Note on CAD Units: AutoCAD is considered "unitless" by design. The definition of a line in AutoCAD is always something like "0,0 – 10,10." In this case, the line is extending from the coordinates 0,0 to the coordinates 10,10. Note there is no Unit specified – just the numeric coordinates. So no matter what you change the units of the drawing to be, the line will still extend from 0,0 to 10,10. So the term "unitless" is misleading; it's very much hard set to a unit type. What does this mean for you as the designer? You need to be extremely diligent in confirming the units.
You may have received a drawing from a colleague, consultant, or client who previously set the units as, say, architectural inches, while you've meanwhile been working in decimal feet. You may have even unknowingly switched the units or scale of your own drawing at some point.
Here's a simple trick to check the units in AutoCAD:
First, draw a line: Type Line in the Command line. The Command line will prompt you to Specify first point. Click anywhere in your drawing to start the line, and drag the cursor in any direction.
Now type 9 (do not click to continue the line). Press the Enter key and then ESC to exit the LINE command. You now have a line in your drawing that is 9 units long. To determine the actual unit setting (inches, feet, meters, etc.), you can now perform a visual test by comparing the length of this line with an object in the drawing of a known size.
The example drawing below contains our correctly scaled trees, a few correctly scaled cars, and our incorrectly scaled tiny tree to the right. We have also drawn our 9-unit line as described in the steps above, which appears at the bottom center portion of the drawing.
Compare the length of your line with the size of any object in your drawing whose actual size you know. In this case, the line is much shorter than the length of the cars. Because we can safely assume that the line is either 9 inches, feet, or meters long, we can verify that the units of the drawing are currently set in inches (we now know the line is neither 9 feet nor 9 meters long because of its size relative to the cars).
Of course, we could also compare our line with the size of the existing trees in our drawing that are the correct size. In this case, the diameter of the correct tree symbols is several times the length of our line, making feet or meters unrealistic. We must be working in inches.
If you have been working in another unit setting, such as feet or meters, you've found the root of the problem. It's time to ...
Correct Your Units and Scale
Open our Scale tool:
F/X Admin ribbon, Scale button
F/X Planting ribbon, Scale button
F/X Admin pull-down menu
F/X Admin toolbar
or type SetDrawScale in the Command line
The Plot Scale dialog box will open.
In this example, the scale is set to 1" = 240 FT and the Drawing Units are set to Decimal Feet.
We can now correct the scale by changing it to 1" = 20 FT, and correct the Drawing Units to Architectural Inches – what we know to be the correct units for this drawing based on the steps outlined above.
Keep the drawing process simple and logical. Always set a nominal (reasonable) scale such as:
- 1" = 20 FT
- 1" = 100 FT
- 1" = 500 FT
Avoid unorthodox scales such as:
- 1" = 23.5 FT
- 1" = 130 FT
- 1" = 357 FT
If you work in Metric units, our software makes this decision easy by requiring you to select a scale from a list of options, all of which are multiples of 5 or 10.
And of course – we cannot stress this enough – always set your scale before starting work on a drawing. You'll thank yourself later.
- Working With Scale: Proper scale practice is not only essential to Land F/X but to the entire fields of landscape and irrigation design. In this webinar, we do some scale troubleshooting and show you when and how to use scaling techniques such as splitting your drawing into different scales, scaling details, and changing the scale of your entire drawing. (1 hr 4 min)