Original Article Date: December 2006
Updated: February 2011
MicroStation's Auxiliary Coordinate Systems (ACS) now includes a tool to align an ACS with a reference. This tool will allow you to set up, measure and draw using the units of a scaled reference. And..it's easy! The contents of this tutorial is for MicroStation V8 XM Edition - SELECT Update #1 (08.09.03.48) or later and was compiled from discussions on Bentley's news groups.
Download 308.dgn, open it with MicroStation V8 XM Edition SELECT Update #1 (08.09.03.48) or later and follow along to learn something new!
Take a peek at the Model dialog and note the existance of two models:
203Kv Tower - A simple line drawing of a transmission tower drawn at 1:1 and set up in meters.
Plot Layout - An "A" size sheet layout (8 1/2 x 11) with the design model attached as a reference at a scale of 1:250. This model is set up in inches to coincide with the imperial paper size.
Before getting into the ACS tool, let's first take a couple of height measurements.
Navigate to the 203Kv Tower model and using Measure Distance (D+1) - measure the height of the tower.
Note that it measures nearly 37 meters.
Go to the Plot Layout model and measure the height of the same tower that's attached as a reference at 1:250. You should get a resulting distance of about 5.8 inches which is correct for the model that the measurement is being taken in. Remember, this particular model is set up in inches and the paper size you see is an 8 1/2 x 11.
To measure the tower in meters, which are the units it was drawn in, go to Settings > Drawing Scale and set the Working Units to Meters / Centimters. Re-measure the height of the scaled reference and notice that the distance now reads about 0.15 meters.
Still - it's no where near the actual 37 meters since the measuring tools are measuring the distance between the datapoints in the active model. In other words, it's not taking the scale of the reference into consideration. Let's fix all that by using an Auxiliary Coordinate System based on the scale of the reference!
To enable accurate measuring of scaled references, you'll need access to the auxiliary coordinate tool set. These tools are available as a separate tool box via Tools > Auxiliary Coordinates or can be accessed via the Auxiliary Coordinates dialog which you can open from Utilities > Auxiliary Coordinates, or by selecting the Auxilary Coordinates button from the Primary Tools tool box.
To set up an ACS from the scaled reference, select Define ACS (Aligned by Reference) and identify the reference with a datapoint. Look at the dialog and notice that the Scale column is now now populated with the scale the selected reference. Since you might want to keep this ACS in the file, select Copy ACS and enter a name such as Tower. This enables you to easily recognize this particular ASC in the event that others are created in the same file.
Note: An alternative approach is to simply select Create a New ACS and set the scale manually from the available picklist in the Scale column.
The last thing to do is to verify that all of this is working as designed and, of course, the easiest way to do that is to measure the height of the tower in meters.
From the Drawing Scale dialog, select Meters / Centimeters for the units. Select Tower as the ACS and notice that it automatically fills in the scale as being 1:250. Take your height measurement an notice that it's now correct.
A couple of finishing notes:
It's not necessary to create an ACS from a scaled reference. If you prefer, you can simply select the correct "scale" from the Drawing Scale dialog. Of course, this may leave a little room for error so use caution when making your selection.
A huge benefit of using an ACS is that it's stored with the file and is applied to all tools. This enables you to use the scale (and/or rotation) of a reference to measure as well as draw new geometry!
Lastly, you can tidy up the Drawing Scale dialog to only show the information you really need.
Park it in your status bar and you're ready to go!
AskInga Article #308