SAE AIR902A describes a practical system for a user to determine observer-to-aircraft distances. These observer-toaircraftdistances can be either closest point of approach (CPA) distances during field measurements or overhead distancesduring acoustic certification tests. The system uses a digital camera to record an image of the subject aircraft. A method ofusing commercial software to obtain the distance from such an image is presented. Potential issues which may affectaccuracy are discussed.