Document Information
Document Type: FAQ
Product(s): MicroStation V8
Version(s): All
Original Author: Bentley Technical Support Group
Legacy Document Number: 6206
What is a unit?
A unit is a definition of distance with which measurements can be performed.
What are working units?
In MicroStation, there is always a set of active [[Working Units]] comprised of a master unit and a sub unit. The working units are used for input and output of distances and points.
What units does MicroStation support?
Out of the box, MicroStation supports the following list of units. These are called "Standard Units":
Why would I want to change the working units?
It can be very convenient. The working units are used for input and output of all distances and points. The measure tools always report distances in working units. Also, working units are used when distances are entered into all dialogs, including AccuDraw.
Unlike Pre-V8 MicroStation, changing the working units does not effect the sizes of the elements. So there is no reason not to use the most convenient working units for a particular task.
How do I change the working units?
Working units are changed using the design file settings dialog box. This dialog can be accessed from the main menu under Settings > Design File.
In this dialog box, choose the "Working units" entry from the list on the far left. Both the master and the sub units can now be changed.
<<Image here>>
Can I change the working units by a key-in?
Yes. The syntax for the key-in is:
SET UNITS [sub unit]
Both "master unit" and "sub unit" should be the name of a known unit (ex. Meter, Foot). Matching of unit names is case insensitive and both singular (ex. meter) and plural (ex. meters) unit names will match.
"Master unit" is required, "sub unit" is optional. If no sub unit is specified, then the sub unit will be set the same as the master unit.
Note: If a space exists within the unit definition, quotes must be used to enclose the unit name when executing this keyin.
Why doesn't MicroStation remember the units that I set?
The working units are "settings", so they are only saved when you enter a "save settings" command. From the main menu, choose File > Save Settings.
If you prefer, settings can be saved automatically whenever you close a DGN file. To do this, choose Workspace > Preferences > Operation >Save Settings on Exit.
Can I use a unit that is not in the default list?
Yes. New units can be defined two ways:
- By using the custom unit dialog box, or
- By supplying a unit definition file.
How does the custom unit dialog box work?
You can use this dialog box to define new master or sub units in terms of the Standard Units. First choose the option "Define Custom Unit" for either the Master or Sub Unit definition.
The line of items that appears can be read like a sentence. For example, the master unit in the picture has been defined as:
3.0 cu is equal to 2.0 Feet
So one cu is the same as 2/3 foot or 8 inches.
It is best to use whole numbers in the custom unit definition. If fractions are used the unit definition will not be exact. This is especially true if a repeating decimal is used, 0.333333 is not exactly equal to 1/3.
<<image here>>
What about Dimensions?
Dimensions can be created using either the active working units or a specific unit defined in the dimension style. For more information, see the MicroStation Dimensions FAQ.
Do all the models in a DGN file share the same unit settings?
What does the Advanced button do?
Important: The resolution setting should NOT be changed during normal operation. This setting is provided to enable user intervention in the case that V8 does not correctly handle the conversion of units between V8 and Pre-V8 files.
When the resolution is changed, the effective size of all graphical elements is also changed. This also changes the maximum size of the model. The maximum size if listed under Working Area: Total. No elements can be placed outside of this area.
Why is the total working area limited?
Note: The allowable working area in V8 is approximately 2 million times larger than it was before V8.
What is the Solids Working Area?
The solid modeling kernels used by MicroStation require coordinate data at a fixed precision. In order to guarantee enough precision is available, MicroStation defines the solids working area. Solid modeling operations outside of this region are not guaranteed to be successful.
The size of the solids modeling area can be increased, but doing so will reduce the available precision.
How does V8 handle the conversion of units from Pre-V8 files?
When a pre-V8 file is loaded, this label is translated using the following table:
| ui | = | microinches |
| ti | = | tenth of an inch |
| i in " | = | inches |
| f ft ' | = | feet |
| yd | = | yards |
| mi | = | miles |
| um | = | micrometers |
| mm | = | millimeters |
| cm | = | centimeters |
| dm dc | = | decimeters |
| m | = | meters |
| hm | = | hectometers |
| km | = | kilometers |
| all others | = | meters |
If your Pre-V8 file does not use one of the unit labels listed in the table, you can let V8 know about that unit by adding a line to the custom unit definition file.
Also, if the table does not list the correct unit for a particular label, the custom unit definition file can be used to override the table.
Why are the unit settings in my Pre-V8 file different when I load the file into V8?
If the master unit label in your Pre-V8 file does not match one of the labels in the table above, then MicroStation needs help to correctly convert the unit information. You need to add a line to your custom unit definition file to describe the new unit.
However, if the master unit label is in the table above, it may appear that the unit settings have changed, but in fact they are simply presented differently.
In Pre-V8 the resolution value was displayed in two parts. For example, in the US, many files were set up with 8000 positional units per in and 12 in per ft. When this is brought into V8, the master units become Feet, and the resolution is displayed as 96000 per Foot. (96000 = 8000 * 12).
How does V8 handle units of DWG files?
See Also
MicroStation Desktop TechNotes and FAQs
External Links
Bentley Technical Support KnowledgeBase
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