Scales in MicroStation

                In MicroStation, there are various scales that are relevant to the process of drawing creation. I will try to brief about each scale so as to know how these scales are useful for drawing creation process & also how they are correlated to each other. Below is the list of scales, you would be interested to know about.

  1. Active Scale
  2. Linestyle Scale
  3. Annotation Scale
  4. Detail Scale
  5. Reference Scale
  6. True Scale
  7. ACS Scale
  8. Print Scale

                Let us go through each scale one by one.

1. Active Scale

                Active Scale is a file property, a general purpose scale for all models within the dgn file. Active Scale is useful to scale cells at the time of placement or for scaling elements with Scale tool. It allows ad-hoc scaling of geometry with different scales along the three axes.

2. Linestyle Scale

                Linestyles are of two types, physical and cosmetic (Non physical). Physical linestyles are used to represent real world objects in the drawing. For example, the painted stripes of a parking lot. They don't need scaling whereas cosmetic linestyles needs to be scaled. It is done by the linestyle scale. 

                Scale for individual linestyle can be set through "Linestyle" dialog (Element>Linestyles>Custom). Also a global linestyle scale factor can be applied to the linestyles which also scales all linestyles by that scale. This is controlled through model properties dialog where you either choose to set a global scale factor or set it to use active model's annotation scale.

3. Annotation Scale

                Annotation Scale is a model property which is used to scale annotations in sheets. It is sometimes referred to as sheet scale because it scales the sheet boundary appropriately to keep the relative size of annotations on the sheet constant and readable. It also helps you pre-configure the reference scale of drawing models for attaching on sheets.

                For more information related to Annotation Scale, please refer the blog on Usability of Annotation Scale.

                Note from the above image that Drawing Scale is just the name of the dialog that contains annotation scale and ACS scale settings.

4. Detail Scale

Detail Scale, Reference Scale and True Scale in Reference Attachment dialog.

                Detail Scale is the representation of master:reference scale in terms of sheet's annotation scale. When you want to attach a drawing at a certain detail scale on a sheet, MicroStation does the necessary calculations to figure out the appropriate master:reference scale.

5. Reference Scale (M:R Scale)
                It is the ratio of master units in the active model to the master units in reference model. When sheet is at full scale (Full Size 1=1) and the design model is being scaled down, it is important to scale it by appropriate reference scale factor so as to fit within sheet boundary. When you specify the detail scale of an attachment, the reference scale is calculated by dividing sheet's annotation scale with the detail scale.

                Relation between Annotation Scale, Detail Scale and Reference Scale
                Annotation Scale is the sheet scale which controls the scaling of the sheet boundary. Detail Scale controls scaling of the drawings attached to the sheet and Reference Scale calculates the appropriate scale factor for the reference based on the sheet annotation scale and the detail scale. 

 6. True Scale
                True Scale is considered for two cases: First is for reference attachment when units in the master model and attachment model are different; and second is for placing cell, when the resolution of the cell model and the resolution of the master model are different.

                It deals with transforming units between two models while attaching reference. It specifies the appropriate scale factor to convert actual units in the referenced model to the units in the active model for reference attachment.

                Let's say Model A is in meters and contains a slab of 1m x 1m. Say it is referenced at master:ref scale of 1:1 into Model B whose units are feet-inches. When attached with True Scale ON, it will convert meters into feet & will reflect the true size of the element, i.e. 3.28ft x 3.28ft. If attached with True Scale OFF, it will measure 1ft x 1ft.

7. ACS Scale

                ACS Scale helps you set a customized frame of reference without having to worry about the global frame of reference. For example, if you are modeling a building which is offset from the global origin and is rotated and scaled from the global coordinate system, it is hard to work on geometry inside the building by constantly terpreting every coordinate with respect to the global coordinate system. You can create your own auxiliary coordinate system for each floor of the building in a way that is convenient to you, say from the corner of the floor and rotated parallel to the floor.

                When you set the drawing to a particular ACS Scale, everything you draw or measure gets scaled in terms of that scale. So a line of 1m placed with ACS Scale 1:1 will measure 10m when ACS scale is changed to 1:10.

                For measuring scaled element sizes, it is a very handy tool, but requires that ACS Plane Lock is ON. Suppose a design model is attached into a sheet by scaling down it by 10 times. Now elements in the reference are 10 times smaller. So from the sheet if you want to know the real world sizes, ACS scale will work a treat for it. Just set ACS Scale to 1:10 and the measured sizes will be actual sizes of the elements.

How Annotation Scale and ACS scale are correlated?
                Annotation Scale is a sheet scale which controls the scaling of the sheet boundary and its annotations whereas ACS controls scaling of the drawing elements. When Annotation Scale is changed, as available sheet space is modified, ACS Scale also automatically changes so that a proportionate scaling between sheet size and element size is maintained. But if the ACS Scale is changed, it won't affect the annotation scale setting. This is because Annotation Scale is independent of ACS Scale. As annotation Scale is meant for annotation and sheet boundary scaling, a change in ACS Scale won't reflect in the Annotation Scale.

8. Print Scale

                It is the scale at which you will take paper output from the composed drawing. Print scale is a factor that should be multiplied by measured sizes on the paper to know the real world sizes.

How Annotation Scale and Print Scale correlated?
                If your print area is defined as the sheet boundary, then the sheet's annotation scale becomes the print scale. Let's see how this works. Say you create a sheet of size ANSI A (8.5" x 11") and apply an annotation scale of ¼"=1' (48 times) to cover design model attachments at master:ref scale of 1:1. You have pre-configured the sheet for printing on ANSI A paper at a print scale of ¼"=1'. If you open the Print dialog, set print area to Sheet and pick ANSI A paper, then the print scale is ¼"=1'. Remember to place a text field in your title block that shows the sheet's annotation scale (¼"=1').

Additional Scale settings for Dimensions and Pattern
                Apart from the above scales there are some additional scale settings for dimensions and Patterns.

  • Dimension Scale

Dimensions Scale setting is available under Scale section in Units tab of Dimension Style dialog. It offers you to scale dimension values in multiples of the scale factor applied. Resultant "dimension value" will be displayed as a multiple of dimension scale factor and the element's size. This will be stored with the dimension style.

  • Reference Scale for Dimension

This setting is accessed either through Scale section in Units Tab or through Placement settings in Advanced Tab in Dimension Style dialog. It allows you to dimension the elements in the reference with its true size. Though the elements in the reference are scaled by reference scale, it allows you to display actual sizes of the elements.

  • Pattern Scale

Pattern Scale is set in the Pattern Area tool setting dialog. It scales active pattern or active pattern cell within that patterning area.


                The following chart shows various scales the afore-mentioned scales being used at different stages in drawing creation & sheet composition process.

 More blogs are coming up so be there: