#### Creating Datums

A datum is a theoretically perfect plane, point, or axis reference feature. A dimensional measurement is made from a datum. Datums are used by Feature Control Frames (FCFs) when displaying GD&T information. In order to define the datums used in FCFs, you should first create the features in your plan that will become the datums. These features can come from auto features or constructed features.

1. First, create the features that will be datum features. These can be auto features or constructed features.

2. Click the Datum (Plan) icon from the Dimensions (Plan) toolbar. The Create Datum Command dialog box appears.

Create Datum Command dialog box

3. Type the datum's ID in the Datum box. Planner will default to the next available datum letter.

4. Select the feature to use as the datum from the list of features. Planner highlights the selected feature in the Graphics Display window.

Note: When selecting features use the following dialog box options:
• Typing the needed feature name in the Search ID box and the feature will be highlighted in the Feature list box when you press the TAB key.
• Selecting the last of a certain number of features by typing the needed number in the Select Last # box. For example, if you wanted to select the last four features that were created, simply type 4 and press the TAB key. PC-DMIS will highlight the features selected in the Feature list box.
• Click Clear to clear the previously selected features.

5. Click Create. Planner inserts the datum into your inspection plan.