1.2.10-3 Reference Aids for Object Displays

A perceptually distinct reference aid should be provided in an object display to support operators in recognizing abnormalities in the object's characteristics.

Additional Information:
When a change in an object's characteristics (e.g., its shape) is the perceptual feature that indicates a fault or abnormal condition, perceptual cues can assist operators in detecting the change. If shape is used, the graphic display should include the normal reference point to which operators can compare the current shape. Reference points are especially useful when the abnormality is slow to evolve, and the integral object is changing slowly.