Encl. (1) to COMDTINST 16577.2
USCG DGPS CONOP
2. OPERATIONAL REQUIREMENTS
___________________________________________________________________________
2.1 Customer Needs
The DGPS Tentative Operational Requirements (TOR) document, G-NRN memorandum dated 5
Dec 1990, identified four missions to be supported by DGPS:
Harbor and Harbor Approach (HHA) .navigation
Vessel Traffic Service (VTS)
Aids To Navigation (ATONE) positioning.
Exclusive Economic Zone (EEZ) surveying
HHA is the only listed mission that requires a navigation capability for both government and public
users. The other three are government missions requiring a positioning service. HHA, being
considered the highest risk mission, was therefore chosen for concentrated analysis. The goal was
to accurately model the HHA mission; then utilize the model to derive measurable performance
values for the DGPS service.
In addition to the four missions listed above, the Coast Guard is cooperating with the U.S. Army
Corps of Engineers (USACE) to implement DGPS service along inland rivers. As a result, USACE
surveying, positioning, dredging, revetment maintenance, and other navigation related activities
will be more efficient. A memorandum of agreement between the USCG and US Army was signed
in February 1994.
The Coast Guard will use the DGPS service for its own missions, and will make it available to both
the general public and other government agencies. Some applications that have been identifidd by
G-N include VTS (dependent surveillance), low visibility search and rescue operations, Q-route
survey support, and Automated Aid Positioning System (AAPS) aboard ATON servicing units.
Most importantly, a DGPS service will ensure that a harbor and harbor approach (HHA)
radionavigation service will be provided to meet the accuracy, reliability and integrity requirements
outlined in the Federal Radionavigation Plan (FRP).
2.2 Performance Measurements
Traditionally, radionavigation system critical performance is defined In terms of accuracy,
integrity, availability, reliability, and coverage. Appendix B gives definitions for these five
performance measures from the 1992 FRP. The U.S. Coast Guard has extensive experience in
specifying navigation service alarm thresholds to ensure safe oceanic (OMEGA) and coastal
(LORAN) radionavigation. However, in the transition from coastal to harbor navigation the
probability of vessel collision or grounding clearly increases. The DGPS service is intended to
improve HHA navigation safety under all weether conditions. Therefore, integrity and reliability
parameters had to be established to levels that would significantly reduce the risk of any navigation
casualty while traversing harbor areas. Values for accuracy and availability set by the 1992 FRP are
summarized in Table 2-1. The positioning user values come from the requirement statement
provided by G-NSR, G-NVT, NOAA, and USACE. HHA accuracy value is set within the 8-20
2
Previous Page
