The sensible echo

Lynn Poole opens the program with a brief history of radar. Dr. J.W. Gebhard, research psychologist with the Johns Hopkins Applied Physics Lab (APL), explains that his job is to improve the way men interpret radar pictures on an A-scope. He then demonstrates a PPI (plan position indicator) scope, which uses a bearing dial and cursor to locate a target. Dr. Albert Stone, a physicist with the APL, explains that RADAR is an acronym for "radio detection and ranging," which measures unknown distances accurately. He demonstrates radar's principles and explains how it works, including the radar antenna that indicates direction. A film shows a police radar speed meter in operation. This is doppler radar, measuring only velocity. Other film clips show the use of radar at sea for guiding ships into harbors, air radar for a flight across Lake Erie, and storm forecasting radar. Dr. Gebhard describes ground control approach (GCA) radar including a film of one hour of airplane flights compressed to a few minutes.