Ordinate dimensions measure the perpendicular distance from an origin point called the datum to a feature, such as a hole in a part. These dimensions prevent escalating errors by maintaining accurate offsets of the features from the datum.
Ordinate dimensions consist of an X or Y value with a leader line. X-datum ordinate dimensions measure the distance of a feature from the datum along the X axis. Y-datum ordinate dimensions measure the distance along the Y axis.
The location and orientation of the current UCS determines the ordinate values. Before creating ordinate dimensions, you typically set the UCS origin to coincide with the datum.
After you specify the feature location, you are prompted for the leader endpoint. By default, the leader endpoint that you specify automatically determines whether an X- or a Y-datum ordinate dimension is created. For example, you can create an X-datum ordinate dimension by specifying a location for the leader endpoint that is closer to vertical than horizontal.
After creating an ordinate dimension, you can easily relocate the dimension leader and text using grip editing. The dimension text is always aligned with the ordinate leader line.