Development of the portable pilot unit (PPU) in the United States began in 1980 through the efforts of the U.S. Coast Guard Research and Development Center, the Johns Hopkins Applied Physics Laboratory, and Capt. Joseph Bradley of The Pilots’ Association for the Bay and River Delaware.
But the electronics of the day and the limits of LORAN-C radio navigation systems made them bulky and limited their accuracy to about 30 feet. When GPS was opened to civilian use in the 1990s, the story changed. Two private entities, Starlink Inc. and Raytheon Service Co., joined Bradley in the project with the goal of turning the PPU into a commercially viable product.
In 1994, the Pilots’ Association for the Bay and River Delaware became the first U.S.-based pilotage group to equip all of its pilots with PPUs. In the 25 years that have followed, virtually all U.S. pilot groups have equipped their members with PPUs supplied by a number of commercial vendors.
Clayton Diamond, American Pilots’ Association