Resolution MSC.112(73)
PERFORMANCE STANDARDS FOR SHIPBORNE GLOBAL POSITIONING SYSTEM (GPS) RECEIVER
EQUIPMENT, REVISED IN 2000
(adopted
on 5 December 2000)
THE
MARITIME SAFETY COMMITTEE,
RECALLING
Article (28(b) of the Convention on the International Maritime Organization
concerning the functions of the Committee,
RECALLING
ALSO resolution A.886(21), by which the Assembly resolved that the function of
adopting performance standards and technical specifications, as well as
amendments thereto shall be performed by the Maritime Safety Committee and/or
the Marine Environment Protection Committee, as appropriate, on behalf of the
Organization,
RECALLING
FURTHER that, in accordance with resolution A.815(19) by which the Assembly
adopted the IMO policy for the recognition and acceptance of suitable
radionavigation systems intended for international use to provide ships with
navigational position-fixing throughout their voyages, the Global Positioning
System (GPS) has been recognized as a possible component of the world-wide
radionavigation system,
NOTING
that shipborne receiving equipment for the worldwide radionavigation system
should be designed to satisfy the detailed requirements of the particular
system concerned,
RECOGNIZING
the need to improve the previously adopted by resolution A.819(19) performance
standards for shipborne GPS receiver equipment in order to ensure the
operational reliability of such equipment and taking into account the
technological progress and experience gained,
HAVING
CONSIDERED the recommendation on the revision of resolution A.819(19) made by
the Sub-Committee on Safety of Navigation at its forty-sixth session,
1.
ADOPTS the Recommendation on Performance Standards for Shipborne Global
Positioning System (GPS) Receiver Equipment, revised in 200Wset out in the
Annex to the present resolution;
2.
RECOMMENDS Governments to ensure that GPS receiver equipment:
a) if installed on or after
1 July 2003, conform to performance standards not inferior to those specified
in the Annex to the present resolution; and
b) if installed before 1
July 2003, conform to performance standards not inferior to those specified in
the Annex to resolution A.819(19).
Annex.
RECOMMENDATION ON PERFORMANCE STANDARDS FOR SHIPBORNE GLOBAL POSITIONING SYSTEM
(GPS) RECEIVER EQUIPMENT, REVISED IN 2000
1.1
The Global Positioning System (GPS) is a space-based positioning, velocity and
time system that has three major segments: space, control and user. The GPS
space segment will normally be composed of 24 satellites in six orbits. The
satellites operate in circular 20,200 km orbits at an inclination angle of 55°
with a 12-hour period. The spacing of satellites in orbit will be arranged so
that a minimum of four satellites will be in view to users world-wide, with a
position dilution of precision (PDOP) of = 6. Each satellite transmits on two
"L- band frequencies, L1 (1575,42 MHz) and L2 (1227,6 MHz). L1 carries a
precise (P) code and coarse/acquisition (C/A) code. L2 carries the P code. A navigation
data message is superimposed on these codes. The same navigation data message
is carried on both frequencies.
1.2
Receiver equipment for the GPS intended for navigational purposes on ships with
maximum speeds not exceeding 70 knots should, in addition to the general
requirements contained in resolution A.694(17), comply with the following
minimum performance requirements.
1.3
These standards cover the basic requirements of position-fixing for navigation
purposes only and do not cover other computational facilities which may be in
the equipment.
2.1
The words GPS receiver equipment as used in these performance standards include
all the components and units necessary for the system properly to perform its
intended functions. The equipment should include the following minimum
facilities:
.1 antenna capable of
receiving GPS signals;
.2 GPS receiver and
processor;
.3 means of accessing the
computed latitude/longitude position;
.4 data control and
interface; and
.5 position display and, if
required, other forms of output.
2.2
The antenna design should be suitable for fitting at a position on the ship
which ensures a clear view of the satellite constellation.
3. PERFORMANCE STANDARDS FOR GPS RECEIVER
EQUIPMENT
The
GPS receiver equipment should:
.1 be capable of receiving
and processing the Standard Positioning Service (SPS) signals as modified by
Selective Availability (SA) and provide position information in latitude and
longitude World Geodetic System (WGS)-84 co-ordinates in degrees, minutes and
thousandths of minutes and time of solution referenced to UTC (USNO). Means may
be provided for transforming the computed position based upon WGS-84 into data
compatible with the datum of the navigational chart in use. Where this facility
exists, the display should indicate that co-ordinate conversion is being
performed, and should identify the coordinate system in which the position is
expressed;
.2 operate on the L1 signal
and C/A code;
.3 be provided with at least
one output from which position information can be supplied to other equipment.
The output of position information based upon WGS-84 should be in accordance
with international standards*;
.4 have static accuracy such
that the position of the antenna is determined to within 100 m (95%) with
horizontal dilution of precision (HDOP) = 4 (or PDOP = 6);
.5 have dynamic accuracy
such that the position of the ship is determined to within 100 m (95%) with
HDOP = 4 (or PDOP = 6) under the conditions of sea states and ship's motion
likely to be experienced in ships**;
______________
* IEC Publication 61162.
** Refer to resolution A.694(17), Publications
IEC 6721-3-6, IEC 6945 and IEC 61108-L
.6 be capable of selecting
automatically the appropriate satellite-transmitted signals for determining the
ship's position with the required accuracy and update rate;
.7 be capable of acquiring
satellite signals with input signals having carrier levels in the range of -130
dBm to -120 dBm. Once the satellite signals have been acquired, the equipment
should continue to operate satisfactorily with satellite signals having carrier
levels down to -133 dBm;
.8 be capable of acquiring
position to the required accuracy, within 30 min, when there is no valid
almanac data;
.9 be capable of acquiring
position to the required accuracy, within 5 min, when there is valid almanac
data;
.10 be capable of
re-acquiring position to the required accuracy, within 5 min, when the GPS
signals are interrupted for a period of at least 24 h but there is no loss of
power;
.11 be capable of
re-acquiring position to the required accuracy, within 2 min, when subjected to
a power interruption of 60 s;
.12 generate and output to
display anchdigital interface* a new position solution at least once every 1
s**;
_______________
* Conforming to the IEC 61162 series.
** For craft meeting the HSC Code, a new
position solution at least every 0.5 s is recommended.
.13 have a minimum
resolution of position, i.e. latitude and longitude, of 0.001 minutes;
.14 generate and output to the
digital interface course over the ground (COG), speed over the ground (SOG) and
universal time co-ordinated (UTC). Such outputs should have a validity mark
aligned with that on the position output. The accuracy requirement for COG and
SOG should not be inferior to the relevant Performance Standards for Heading*
and SOME**;
______________
* Resolution A.424(XI).
** Resolution A.824(19).
.15 have the facilities to
process differential GPS (DGPS) data fed to it in accordance with the standards
of Recommendation ITU-R M.823 and the appropriate RTCM standard. When a GPS
receiver is equipped with a differential receiver, performance standards for
static and dynamic accuracies (paragraphs 3.4 and