ACS (Auxiliary Coordinate Systems)


The ACS tools have been significantly improved in current versions of MicroStation-based products. In fact, ACS actually replace the need for Depth Lock (note that Depth Lock has been removed in favor of using ACS).

If the tool is not visible, right‐click on the Primary Tools frame and turn on Auxiliary Coordinates:

This icon either opens a pop‐down or floating dialog like the others in this tool frame.

There is also a toolbox, but as all of the tools are now in the ACS dialog (above) it is not really needed. The toolbar contains three groups of tools. The middle four tools allow you to define a new ACS by different methods.

Creating A New ACS

 The tool that I think is most useful is Define ACS by Points. It is the clearest tool to use as it requires you to visually select the origin, then X and Y axes.

This is relevant to setting out drawings as the origin point is defined first then the X axis, use this if creating an ACS that will be used for Setting Out.

Define by Element sets the origin as the point that you select on the chosen element but aligns the X axis automatically, not necessarily the way you want. The other methods do not allow the origin to be selected.

Currently, there is the step required to save an ACS after creating it. Once the Create ACS by Points command is complete, the new ACS will be listed at the top of the dialog as View n : Unnamed.

To save this ACS right‐click on it and pick Copy. The new ACS will then be added to the list below as Unnamed where it should be then be renamed appropriately.

You can create as many ACS as you need (or can keep track of!). ACS can be created in any orientation:

Creating A Quick ACS

Define ACS by Face is a very quick way to set up a temporary or file specific ACS that relates to a building element, pick the solid and then the appropriate face, the position of the ACS can be moved around by its centre to snap to a relevant point or rotated or flipped using the axis widgets

ACS and Views

A feature introduced in V8i is that the ACS can be different in each view.

Note in the dialog above that the Active ACS is shown at the top of the list as View 2 : Block 3 Ground. It is also highlighted in turquoise in the list of ACS. Double click any other in the list to change ACS. However be aware that double clicking will only set that ACS active in the current view. To set all views to that ACS right‐click and pick Set All Views.

For example, setting the ACS to ‘Block 1 Second’ in the View 1 (Top view) allows you to start placing an element in the Top View at the desired ACS Z‐height or rotation without changing the ACS being used or other operations in other views. The critical thing is to be aware of the ACS in the view where you start element placement.

To Apply ACS To All Views

Open ACS Toolbox from Tools menu > Coordinate Systems > ACS > Open as Toolbox

Dock this toolbox, it will show as a single icon, use the Apply ACS to Selected View tool (no 8), in the tool settings there is an option to Apply To All. When this is ticked, it is saved in your preferences. This gets around the View independent ACS that is the default.

Once this setting has been applied selecting an ACS the ACS Selector in the Drawing Scale dialog will apply to all views.

ACS And View Rotation

Note that the standard named views are all relative to the active ACS. For instance if you select Isometric view when an ACS at an unusual orientation is active you may wonder why the site is at an odd angle!

Modifying ACS

It is often as quick and more reliable to create a new ACS than to move or modify an existing one. Rotate ACS requires the rotation angles to be worked out then keyed in. Move ACS is useful if you just want to relocate the ACS origin. As with ACS creation the moved ACS has to be copied to the list and renamed.

ACS can be modified by direct input to the listed values. For instance Building 1 First Floor can be copied and renamed to Building 1 Second Floor. The Z value can be edited to change to the next floor level.

Select ACS

Using the Select ACS tool (at right hand end of the toolbox) will show all of the existing ACS and their names in all open views, the active ACS in colour, any others in grey. The required ACS can be selected by clicking on it.

Drawing Scale Dialog

The Active ACS can also be set from the pop‐up list in the Drawing Scale dialog. This is opened from the Settings menu > Drawing Scale. It should be docked at the bottom of the MicroStation window with the subunit and ACS Scale items turned off.

Selecting an ACS from this pop‐up will only set the ACS for the Active View.


Note that toggling the Lock ACS button will toggle both the ACS Plane and ACS Plane Snap Locks on/off. Both of these locks are generally needed to constrain element placement to the active ACS plane.

ACS Plane Lock – locks your datapoints to the active ACS

ACS Snap Lock – locks your snaps to the active ACS

Importing ACS

It is obviously tedious and time consuming to repeatedly create ACS. Where appropriate a project seed file can be pre‐populated with ACS. Or if the ACS are created as the project proceeds they can be imported into the active file or the project seed file.

If the ACS change as the project proceeds updated ACS can be imported, duplicate named ACS will be added to the ACS list and named with a suffix:

ACS and AccuDraw

If you use the AccuDraw P shortcut for precision key‐in, there is an option to set the coordinates relative to the active ACS.

As with the other features you have to be careful to ensure the correct ACS is active.

ACS and Coordinate Placement

Any coordinates placed using the Label Coordinates tool will be relative to the active ACS. This can be very useful when placing coordinates relative to a site datum

Again be sure that the correct ACS is active when placing Label Coordinates.

When using this tool, the label is accurately generated by the selected point, but no visible marker is placed. Once placed the coordinates are simple text, they will not update if moved or copied and there is no recorded connecting the label and the active ACS at placement.

Another approach to placing coordinates is using Text Fields. However, at present Text Fields that contain Element Properties, such as the x,y.z coordinates of a point, do not recognize the active ACS, they always display the coordinates relative to the model file’s Global Origin.