Encl. (1) to COMDTINST 16577.2
USCG DGPS CONOP
In 1989, the U.S. Coast Guard modified the existing marine radiobeacon located at Montauk Point,
New York to broadcast differential corrections in the RTCM SC-104 format. The Montauk Point
field tests demonstrated that MSK modulation of an existing radiobeacon signal was effective in the
transmission of RTCM SC-104 format corrections. Also, MSK modulation could be used with no
adverse effect on the automatic direction finding receivers of traditional maritime radiobeacon
users. Important to both the U.S. Coast Guard and the public; MSK technology is economical to
implement at existing radiobeacons and within user receivers. By January 1990, the RTCM
published the SC-104 format version 2.0 document establishing a formal U.S. industry differential
GPS (DGPS) correction format. With the RTCM SC-104 standards and the initial radiobeacon
broadcast success, Montauk Point began the first continuous public U.S. DGPS broadcast on
August 15, 1990. This transmission marks the beginning of the U.S. Coast Guard's transition from
DGPS research and development to implementation of a U.S. maritime DGPS service.
C-2