Modeling for the field and/or layout demands more precision than your standard visualization model. If you’re based in the US, this is especially important. In Revit, for example, the units may be set to show up to 1/16 or 1/8 inches of precision. This means any dimension less than 1/8 of an inch will simply round up – a nice plus if you're creating sheets but a shock to anyone using a model for layout.
The good news is that you can set up your model to show dimensions much more accurately using decimal units. Here's a quick overview of how to change the way your units are displayed in the two authoring programs we use the most.
How to Use Decimal Units in Autodesk Revit
You can fine tune how Revit shows units by changing the overall project units or by overriding the default dimension parameters.
Overall project units affect any dimensions that are using the standard measuring system as the default. To change the defaults, go to the Manage ribbon and choose Project Units. The standard setting is in feet and fractional inches, but you can change this to decimal feet instead. More importantly, you can specify the number of decimal places.
Make sure to keep an eye on related dimensions. Aligned dimensions, linear dimensions and the rest of the dimension-based families all need to be set to pull from the defaults mentioned above or overridden. To do this, select an existing dimension family and change the type properties to display “Use project settings” in the units format property. Of course, you can override this parameter if you need an alternate dimension type.
How to Use Decimal Units in Autodesk AutoCAD
Changing the units in AutoCAD is very similar to Revit. You have overall units (specified in Dimension Styles) and then dimension overrides within properties that may or may not use the overall units.
Use the DIMSTYLE command in the command window to access the dimension styles in the file. You can usually edit the “Standard” style (the default in a typical AutoCAD file). Within the DIMSTYLE dialog box, click on the Primary Units tab to specify decimal units format and precision for that style.
From there, any dimension you create with the “Standard” dimension style will display those units. As with Revit, you can override how those dimensions are shown individually in the properties. Use the MO command to bring up the properties window and click on one or more dimension objects. From there you can edit (i.e., override) nearly any option manually. Try to avoid doing this too often as it will prove more difficult to change dimensions en masse if you change your mind later.
Zack Creach is a senior engineer for Holder Construction in Atlanta.