Original Article Date: Jan 30, 2001
Learn all about MicroStation V7's working units while drinking beer...or is that drinking units while working beer?
Authors Note: Portions of this article have appeared in the May 2000 issue of the MicroStation Manager Magazine
If you think of your MicroStation design file as a huge piece of ‘grid' paper you'll actually find it very easy to understand working units.
First of all we need to know that the design file in 2D is called a Design Plane and is a fixed size of 4,294,967,296 units or positional units along both the X and Y axis. In 3D the file is actually called a Design Cube and the Z axis also has the same number of units.
You can think of the Positional Units (PU's) as simply the distance between the grids on a piece of graph paper…each unit being equal and fixed in size. In MicroStation the PU is the smallest measurable distance that can be made.
Imagine if you will that there are 4,294,967,296 of these little fixed units in the design plane/cube…I would've drawn more but that would've been crazy!
OK, so now that the Positional Unit has been explained – Let's look at the Working Units…you know…That master unit and sub unit stuff!
Working Units in MicroStation is simply defining a relationship between the positional units and your preferred unit of measure – say meters for instance.
Working units are file independent, can be set up on a per-file basis but are typically set up in your seed files.
To set up the working units go to Settings > Design File > Working Units. Let's take a look at how to define the working units of a metric design file:
In the Unit Names category the entry fields for Master Units and Sub Units are just one or two character labels for your units of measure. For instance Meters m and Centimeters cm, or Feet ft and Inches in, or how about Cases of Beer CB and Bottles of Beer bb!
The Resolution category is where we're gonna specify how MicroStation is going to count out the positional units and how they will be applied to your units of measure.
The first field asks for the number of sub-units per master unit…so we could fill 100 since there are 100 centimeters in 1 meter. Likewise, we would enter 12 for an imperial file set up in feet and inches. (How about 24 bottles of beer in 1 case?)
The second field requires a number that tells MicroStation how many positional units to count to make one sub unit…keep in mind that the positional unit is the smallest measurable distance you can have. For our metric example we could use a value of 100, that would mean that there would be 100 pu's in one centimeter thus allowing us to draw down to 1/100th of a cm!
The Working Area category reports back to us how large of an area we now have to work with in master units. The more pu's per su – the smaller the working area and a finer resolution or accuracy can be obtained. This value is calculated by dividing 4,294,967,296 by (sub units X positional units). Even though this number changes when you change your resolution, the size of the design plane as expressed in positional units always remains the same – 4,294,967,296 of them!
Well that's about it. Ah, one last thing…working units are most often set up in the seed file and normally should not be changed in mid-design. To do so will cause MicroStation to measure the elements differently and you may not be able to set it back. Also, after you have changed your working units do a File > Save Settings or be sure to have Save Settings on Exit enabled from Workspace Preferences.
AskInga Article #36