UNITS

Do you work in Meters? Feet? Inches? Angstroms? Parsecs? Qell'gams?

Be aware of your UNITS.

The main units I personally work with are either Decimal for Civil drawings or Architectural for Mechanical, Structural and Architectural drawings.

In decimal units, one unit is usually 1 foot (Civil), 1 meter (metric Civil), 1 millimeter (metric Arch, Mech, and Struct), etc.

In Architectural units, one unit represents one inch. 

There are other Units settings in AutoCAD of course including Engineering, Fractional, and Scientific.

For now I'm just going to cover Decimal and Architectural.

You can set drawings to be Architectural, or Decimal (among others) and when you insert one drawing into another, AutoCAD will scale the drawing up or down automatically as necessary depending on the units and the INSUNITS system variable.

See Help > Insert Units. 

This automatic scaling can work well in an environment that deals with both Architectural drawings and Civil drawings. It can also be confusing for the older, uh, I mean seasoned AutoCAD users. While I admit the automatic scaling can be useful, we set all our drawings' INSUNITS to Unitless and allow the designers/drafters to scale up or down by 12 as they see fit. We have so many drawings that I feel automatic scaling would actually confuse people or scale the drawings the wrong way if the setting wasn't set right.

If you really have some interesting UNITS or have a lot of conversions going on check out the AutoCAD Unit Definition file in Help. I have to admit, I've not had a reason to mess with it that much... none at all, actually.

Many people (like us) just use Unitless for the Units setting. Type UNITS and check out the settings in the dialog box.

When Insertion scale is set to Unitless, (INSUNITS = 0) copying objects from a Decimal drawing to an Architectural drawing will require you to scale the objects up by 12 and vic-versa.

If each drawing's Insertion Scale or INSUNITS is set to its own units, AutoCAD will automatically scale the drawing accordingly when it is inserted or xreffed into another drawing.  

If you work in a multi-discipline office where you use a variety of units, get to

know the following variables.

- INSUNITS

- INSUNITSDEFSOURCE

- INSUNITSDEFTARGET

Metric to Imperial has it's own scaling issues too: 25.4 or 0.3048, etc.

If you are designing in metric and printing to 11x17 or some other American paper size, your paperspace print scaling will have to be adjusted accordingly (like 25.4)  if you want to print a 1:5,000 metric drawing to scale on American size paper. 

We work in a multi discipline office where we pass drawings around and use xrefs that may be Decimal or Architectural. Many time people have questions about their measurements. A building on a site plan should not measure 6'-8" long. It's really 80' long and the units are just reporting that distance in Architectural units. The units for a Civil drawing should be set to Decimal. The dimension style should usually reflect the current UNITS settings. 

Long ago, I customized our menus so we could easily set up a drawing for Civil or Architectural drawings. With one click of a menu pulldown, all the UNITS, system variables, and dimension styles are properly set for the appropriate drawing by using a couple of simple script files.  This could be a topic for another blog. So, if anyone is interested in this please leave a comment.  I even taught an AUGI class many years ago on menu customization using this as an example.

When people have problems with their units or dimensions, I'll ask them to take a DISTance between two points. ...Note that was a distance, not a dimension....  If the distance does not make sense (like the 6'-8" long building mentioned above) change the units and take another distance. This is an easy method of determining what distance a unit is. Foot, Meter, Inch, etc. 

So, in short, when confused, take a distance (DIST) to determine what units your drawing is set up in. Adjust your UNITS and DIMSTYLE accordingly.

I hope this has helped anyone who may work in a multi discipline office like myself.  There is still much that can be discussed, but this is enough for now, I think. I don't want to bore you too much. (Too late maybe, eh?) 

By the way, this has been another expanded excerpt from my AutoCAD Weekly Planner available from the Autodesk App Exchange. There are two versions for under $5. You can also find my "52 AutoCAD Tips Tricks and Little Known Commands" book for the Kindle from Amazon.com or directly from your Kindle for only $0.99. See link below

Lyle's 52 AutoCAD Tips on the Kindle

'till next time.

Later,

Lyle.