"Gary Drescher" wrote in message
news:fcE5d.162720$3l3.118386@attbi_s03...
distance); and 2) if a plane is really passing nearby at 500' AGL, then
its distance from the camera will be less than 1000' AGL over a wide range
of angles.

Oops, that should just say 1000', not 1000' AGL.

--Gary