[Federal Register Volume 59, Number 56 (Wednesday, March 23, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-6813]
[[Page Unknown]]
[Federal Register: March 23, 1994]
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DEPARTMENT OF TRANSPORTATION
Coast Guard
[CGD 94-006]
Announcement of Global Positioning System (GPS) Initial
Operational Capability (IOC) and Its Impact on Vessel Carriage
Requirement Regulations
agency: Coast Guard, DOT.
action: Notice.
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Summary: The Department of Defense has notified the Department of
Transportation that the Global Positioning System (GPS) has reached its
Initial Operational Capability (IOC). A GPS receiver now meets the
carriage requirements for electronic position fixing devices under 33
CFR 164.41 (a)(2).
dates: Effective December 8, 1993, the Coast Guard will accept a GPS
receiver as an electronic position fixing device satisfying the
requirements of 33 CFR 164.41.
addresses: If so indicated, documents referenced in this preamble are
available for inspection or copying at the office of the Executive
Secretary, Marine Safety Council (G-LRA/3406), U.S. Coast Guard
Headquarters, 2100 Second Street SW, Washington, DC 20593-0001 between
8 a.m. and 3 p.m., Monday through Friday, except Federal holidays. The
telephone number is (202) 267-1477.
for further information contact: LCDR Jean Butler, Chief, Radio Aids
Applications and Developments Branch, Radionavigation Division, Office
of Navigation Safety and Waterway Services, USCG Headquarters,
Washington, DC 20593-0001, telephone 202-267-0298. A copy of this
notice may be obtained by calling the Coast Guard's toll-free Boating
Safety Hotline, 1-800-368-5647. In Washington, DC, call 267-0780.
Background
The Federal Radionavigation Plan (FRP), jointly prepared by the
Department of Defense (DOD) and Department of Transportation (DOT) on a
biennial basis, contains further information concerning navigation,
radionavigation system descriptions, and plans for government operated
radionavigation systems. It is available to the public through the
National Technical Information Service (NTIS).
GPS is a DOD-developed, worldwide, satellite-based radionavigation
system that will be the primary radionavigation system well into the
next century. When fully operational, the GPS will be composed of 24
satellites in six orbital planes. The spacing of the satellites in
orbit will be arranged so that a minimum of five satellites will be in
view to users worldwide. Full Operational Capability will be achieved
when 24 operational, production model satellites (Block II or newer)
are operating in their assigned orbits and when the constellation has
successfully completed testing for operational military functionality.
This is not expected to occur until 1995. GPS Initial Operational
Capability (IOC) has been met and means that 24 GPS satellites (any
model) are operating in their assigned orbits, are available for
navigation, and provide the SPS levels of service as defined in the
FRP. Any planned disruption of the GPS in peacetime will be subject to
a minimum 48-hour advance notice provided by the DOD to the Coast Guard
GPS Information Center (GPSIC). A disruption is defined as periods in
which the GPS is not capable of providing Standard Positioning Service
as defined in the FRP. Unplanned system outages resulting from system
malfunctions or unscheduled maintenance will be announced by the GPSIC
as they become known.
GPS provides two levels of service: Standard Positioning Service
(SPS) and Precise Positioning Service (PPS). SPS is the standard level
of positioning, velocity, and timing accuracy that is available to any
user on a continuous worldwide basis. The horizontal positioning
accuracy of this service is 100 meters (2 distance root mean squared
(drms), 95% probability) and 300 meters with 99.99% probability. PPS
will be limited to authorized U.S. and allied Federal government and
military users and to those civil users who can satisfy U.S.
requirements. These requirements are: the use must be in the U.S.
national interest; the user must meet specific GPS security
requirements; and a reasonable alternative to the use of PPS must not
be available. Unauthorized users will be denied access to PPS through
encryption of the signals. PPS military user equipment will provide
horizontal positioning accuracy of 21 meters (2 drms). The SPS is
affected by a process called Selective Availability (SA), which
degrades the basic accuracy of the SPS through adjustment and
encryption of some of the signals and data.
One of the shortcomings of GPS for civil navigation use is its
problem meeting integrity requirements. Integrity is the ability of a
system to provide timely warnings to users when the system should not
be railed upon for navigation. According to DOD's concept of operation,
GPS satellites are monitored more than 95 percent of the time by a
network of five monitoring stations spread around the world. The
information collected by the monitoring stations is processed by the
GPS Master Control Station (MCS) and used to periodically update the
navigation message, including the satellite health message, transmitted
by each satellite. The health message is transmitted as part of the GPS
navigation message for reception by both PPS and SPS users.
Additionally, satellite operating parameters such as navigation data
errors, signal availability failures, and certain types of satellite
clock failures are monitored internally within the satellite. If such
internal failures are detected, users are notified within six seconds.
Other failures detectable only by the control segment may take from 15
minutes to several hours before users are notified of a problem. This
is unsatisfactory for many modes and phases of navigation, and, from
the maritime perspective, it is particularly deficient for the harbor
and harbor approach (HHS) phase of navigation. The integrity required
for HHA navigation will be provided through augmentation of the GPS SPS
by the Coast Guard's Differential GPS (DGPS) service, now being
implemented.
As with Loran-C and Transit (the Navy Navigation Satellite System),
the GPS should not be used by itself in or near restricted waters. As
described above, the accuracy of the system is not monitored
continuously and it may take 2-6 hours to be aware of a problem or fix
a problem with a satellite. Additionally, mariners need to be aware of
the real accuracy of the system. GPS receivers may produce a latitude
and longitude position that appears accurate to several decimal places,
which may mislead a mariner to believe the system is really that
accurate. GPS SPS will only give an accuracy to within 100 meters, with
95% probability. That means that the mariner can be anywhere within a
100 meter radius of the position indicated by the receiver. It also
means that 5% of the time, the actual position could be greater than
100 meters from the indicated location. Mariners must constantly be
aware of this and navigate with due caution, using all means available,
most importantly in more restricted locations such as harbor and harbor
approach areas.
The FRP outlines navigation accuracies required for the different
phases of navigation. While the Ocean and Coastal phases have been
satisfied for some time, the harbor and harbor-approach phase
requirements have been unattainable with existing systems.
Additionally, a similar need for higher accuracy exists for other Coast
Guard missions such as positioning aids to navigation and Vessel
Traffic Services. DGPS is a solution to all of these needs.
DGPS improves upon GPS signals by using a local reference receiver
to correct errors in the standard GPS signals. An ``all in view'' GPS
receiver is located at a site which has been geodetically surveyed. The
receiver monitors all visible satellites and measures the pseudorange
to each satellite. Since the satellite signal contains information on
the precise satellite orbits and the reference receiver knows its
position, the true range to each satellite can be calculated. By
comparing the calculated true range and the measured pseudorange, a
correction term can be determined for each satellite. These corrections
are then broadcast to the user over the communications network, and can
be received by the user with a DGPS receiver. The Coast Guard will be
using selected marine radiobeacons to transmit the corrections to
users. The corrections are then applied to the pseudorange measurements
within the user's receiver, achieving a position accurate within 10
meters, with 95% probability. One advantage of DGPS is that it will
provide radionavigation accuracy that is not possible with existing
systems. It will also reduce the integrity check of satellites from
hours to seconds, and will even allow for use of satellites considered
unhealthy. By knowing its position, the reference station can detect
immediately when a satellite may be sending erroneous data. DGPS
accuracies cannot be achieved with either the GPS Standard Positioning
Service, with Selective Availability on or off, or Precise Positioning
Service. The Coast Guard will also implement an integrity monitoring
system which will verify the accuracy of the corrections that it
transmits on the selected radiobeacon. The Coast Guard's DGPS Service
will be implemented for harbor and harbor approach areas of the
continential U.S., Great Lakes, Puerto Rico, and most of Hawaii and
Alaska by 1996.
Information Availability
Operational status and other information about GPS is available to
worldwide users of GPS through the Coast Guard's GPS Information Center
(GPSIC). The GPSIC sends GPS operational status information to civil
users through Operational Advisory Broadcasts (OAB). These broadcasts
contain the following general categories of GPS performance data:
Current constellation status, Recent (past) outages, Scheduled (future)
outages, and Almanac data. The OAB is disseminated or made available
through the following media:
GPSIC Computer Bulletin Board System (BBS)
GPSIC 24-Hour Status Recording
WWV/WWVH worldwide high-frequency radio broadcasts
U.S. Coast Guard Marine Information Broadcasts (MIB)
DMAHTC Broadcast Warnings
DMAHTC Weekly Notice to Mariners
DMA Navigation Information Network (NAVINFONET)
NAVTEX Data Broadcast
Through a duty watchstander and an electronic bulletin board
service (BBS), both available 24 hours per day, GPSIC also makes the
following information available:
--Operational status of GPS as provided by DOD
--Precise GPS orbit data from the National Geodetic Survey
--Technical information on GPS
--Operational status and information on other Coast Guard operated
radionavigation systems
--Instructions on the access and use of GPSIC services
The U.S. Air Force Second Space Operations Squadron (2SOPS), which
operates the GPS Master Control Station (MCS) in Colorado Springs, CO,
provides the following GPS information for the GPSIC:
Notice Advisories to NAVSTAR Users (NANU) are near real-time
operational status capability reports. NANUs are issued to notify users
of future, current, or past satellite outages, system adjustments, or
any condition which might adversely affect users. NANUs are generated
by 2SOPs as events occur. GPS Status Messages contain general
information that is downloaded daily from the Air Force's (2SOPS)
electronic bulletin board. The message contains information about the
satellite orbit (plane/slot), clocks, and current or recent NANUs.
Status Messages are generated by 2SOPS once a day Monday through
Friday, except on Federal holidays.
Almanacs contain the orbital information and clock data of all the
satellites. The almanac for all satellites can be obtained from
downloading the continuously transmitted data stream from any
satellite.
In addition to receiving information from the MCS, the GPSIC works
with representatives of the National Geodetic Survey (NGS) to offer NGS
computed precise GPS orbit data to the public via the GPSIC bulletin
board. This data is called precise ephemeris data. Precise ephemeris
data describes the orbit of each satellite as observed by numerous
ground stations. It is useful in making a refined determination of
where the satellites were at some time in the past. The time lag for
this information is about eight days.
The BBS is an electronic version of a bulletin board, where
information is made available in easy to access lists and files. Any
user with a computer and modem can dial the BBS and browse through the
information or copy files into their own computer for further use. The
BBS is menu-driven and has an extensive set of on-line help utilities.
If necessary, users can also page the GPSIC watchstander to request
personal assistance. The BBS is free and open to all. However, users
will have to pay their own connection charges (long distance telephone
or public data network costs). First-time callers are asked to register
on-line (provide their names, addresses, etc.) before proceeding to the
BBS main menu. Through the BBS, a wide range of information is
available 24 hours a day. BBS information is updated whenever the other
GPSIC sources are. Users may call the BBS via either telephone or
SprintNet (a public data network). Ordinary telephone is the easiest
for most people, but SprintNet offers a high speed error-free
alternative for those (especially international callers) who may have
difficulty in getting a good data connection over the voice phone
lines. To contact the BBS, call: (tel) 703-313-5910. Modem speeds of
300 to 14,400 bps and most common U.S. or international protocols are
supported. Communications parameters should be set to: 8 data bits, No
parity, 1 stop bit (8N1), asynchronous comms, full duplex. We have
eight phone lines at this number and two auxiliary numbers to
accommodate modems which may be incompatible with the ones on 313-5910.
The BBS SprintNet number is: 31102021323 (or abbreviate to 202 1328 if
accessing SprintNet via telephone to one of their modems.) For
SprintNet access, users must set up their own accounts with Sprint or a
similar public data network which has a ``gateway'' to SprintNet. For
more information, call: (800) 736-1130 (U.S.) or (913) 541-6876)
(international).
Users who need further information or assistance may call the GPSIC
watchstander at 703-313-5900, or write to Commanding Officer, USCG
Omega Navigation System Center, 7323 Telegraph Road, Alexandria, VA
22310-3998.
In addition to the GPSIC watchstander and BBS already described,
users can access the GPS OAB information from the services described
below:
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Service Availability Info type Contact No./Freq
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GPS/Omega voice 24 hours a day... Status forecasts (703) 313-5905.
tape recording. historic.
WWV.............. Minutes; 14 & 15. Status forecasts 2.5, 5, 10, 15
and 20 MHz.
WWVH............. Minutes; 43 & 44. Status forecasts 2.5, 5, 10 and
15 MHz.
USCG MIB......... When broadcast... Status forecasts VHF-FM, med freq
& high freq.
DMA broadcast When broadcast... Status forecast ................
warnings. outages.
DMA weekly notice Published & Status forecast (301) 227-3126.
to mariners. mailed weekly. outages.
DMA Navinfonet 24 hours a day... Status forecasts (301) 227-3351
automated notice historic 300 baud, (301)
to mariners almanacs. 227-5925 1200
system. baud, (301) 227
4360 2400 baud.
For more info (301 227-3296.
call.
Navtex data When broadcast; 4- Status forecast 518 KHz.
broadcast. 6 time/day. outages.
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(Authority 33 USC 1231, 46 USC 2103, 3703, 49 CFR 1.46)
Dated: March 15, 1994.
R.C. Houle,
Captain, U.S. Coast Guard, Acting Chief, Office of Navigation Safety
and Waterway Services.
[FR Doc. 94-6813 Filed 3-22-94; 8:45 am]
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