I love to see old threads like this resurrected.
My avatar is the visualization of the IFGA formula: Image Size, Focal Distance, Object Size/Ground Coverage, Focal Distance (Formula; US Navy photography.) Using the IFGA formula in aerial photography, it is possible to determine the size of an object on the ground in an aerial photograph.
The graphic I use as my avatar was the rating badge of a U.S. Navy Photographer's Mate (PH) during the Vietnam era when I was in. It was later changed to include wings, as Photographer's Mates were considered an aviation rating rather than a "black-shoe" or sea-going rating.
The rating of Photographer's Mate was retired in July of 2006 when the job was merged into the new Mass Communications Specialist (MC).