1 Introduction
1.1 QZSS is a regional navigation satellite system compatible and interoperable with
other navigation satellite systems worldwide. QZSS is a system independently
developed and operated by Japan and is comprised of three major components: space
constellation, ground control segment and user terminals. At the time of QZSS
4-satellite constellation, there are three quasi-zenith orbit (QZO) satellites and
one geostationary orbit (GEO) satellite. QZO is the inclined geosynchronous orbit
(IGSO) with a slight eccentricity. QZO satellites have different orbital planes from
one another that are inclined at about 40° and elliptical. The centre of longitude
at three QZO orbit is around 139° E. Three QZO satellites have an orbital plane
phase that has been adjusted so that they have almost the same ground track and the
orbital period of QZO is the same as GEO. GEO satellite is positioned at 127° E. At
the time of QZSS 7-satellite constellation, two QZO satellites and one GEO satellite
will be added in 4-satellite constellation. Each satellite transmits standard
positioning service signal on "L1" and "L5" bands with carrier frequencies as 1
575.42 MHz and 1 176.45 MHz, respectively. Standard positioning signals include
ranging codes which are defined in the GPS IS documents, i.e. using the same code
sequences as GPS pseudo random noise (PRN) codes and can provide the open service. A
navigation data message is superimposed on these codes. QZSS satellites are
identified by PRN codes. QZSS can be used in combination with GPS.
1.2 QZSS provides positioning, navigation and timing (PNT) service, free of direct
user charges. QZSS receiver equipment should be capable of receiving and processing
the standard service signal.
1.3 QZSS receiver equipment intended for navigation purposes on ships with a speed
not exceeding 70 knots, in addition to the general requirements specified in resolution A.694(17),footnote should comply with the minimum performance
requirements set out below.
1.4 The standards cover the basic requirements of position fixing, determination of
course over ground (COG), speed over ground (SOG) and timing, either for navigation
purposes or as input to other functions. The standards do not cover other
computational facilities which may be in the equipment nor do they cover the
requirements for other systems that may take input from the QZSS receiver.
1.5 It should be noted that this is the regional navigation satellite system being
recognized as a future component of the Worldwide Radionavigation System (WWRNS) and
the service is limited to the following coverage area:
1.6 Figure 1 shows the coverage area of QZSS PNT service.
Figure 1: Coverage area of QZSS PNT Service
2 QZSS receiver equipment
2.1 The term "QZSS receiver equipment", as used in the performance standards,
includes all the components and units necessary for the system to properly perform
its intended functions. QZSS receiver equipment should include the following minimum
facilities:
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.1 antenna capable of receiving QZSS signals;
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.2 QZSS receiver and processor;
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.3 means of accessing the computed latitude/longitude position;
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.4 data control and interface; and
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.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, taking into consideration any
obstructions that might exist on the ship.
3 Performance standards for QZSS receiver equipment
QZSS receiver equipment should:
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.1 be capable of receiving and processing the QZSS navigation signals, and
use the ionospheric model;
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.2 provide position information based upon ITRF or WGS-84 coordinates and
should be in accordance with international standards;footnote
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.3 provide time referenced to Universal Time Coordinated (UTC);
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.4 be provided with at least one output from which position information, UTC,
COG, SOG and alarms can be supplied to other equipment. The output of UTC,
COG, SOG and alarms should be consistent with the requirements of paragraph
3.15;
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.5 have static accuracy such that, for the service area in figure 1 where a
horizontal dilution of precision (HDOP) is equal to or less than 6.7, the
position of the antenna is determined to be within 50.4 m horizontal
(95%);
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.6 have dynamic accuracy under the conditions of sea states and ships' motion
likely to be experienced in ships,footnote such that for the service area in figure 1
where a HDOP is equal to or less than 6.7, the position of the antenna is
determined to within 50.4 m horizontal (95%);
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.7 have position information in latitude and longitude in degrees, minutes
and thousandths of minutes with a position resolution equal to or better
than 0.001 min of latitude and longitude;
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.8 be capable of selecting automatically the appropriate
satellite-transmitted signals to determine the ship's position and velocity,
and time with the required accuracy and update rate;
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.9 be capable of acquiring satellite signals with input signals having
carrier levels in the range of -134 dBm to -124 dBm. Once the satellite
signals have been acquired, the equipment should continue to operate
satisfactorily with satellite signals having carrier levels down to -137
dBm;
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.10 be capable of operating satisfactorily under normal interference
conditions consistent with the requirements of resolution A.694(17);
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.11 be capable of acquiring position to the required accuracy, within 30 min,
when there is no valid almanac data;
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.12 be capable of acquiring position to the required accuracy, within 5 min,
when there is valid almanac data;
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.13 be capable of re-acquiring position to the required accuracy, within 2
min, when subjected to a power interruption of up to 60 s;
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.14 generate and output to a display and digital interfacefootnote a new position solution at least once every 1
s for conventional craft and be recommended at least once every 0.5 s for
high-speed craft;
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.15 provide the COG, SOG and UTC outputs with a validity mark aligned with
that on the position output. The accuracy requirements for COG and SOG
should not be inferior to the relevant performance standards for
headingfootnote and speed and distance measuring equipment
(SDME)footnote and the accuracy should be obtained under the
various dynamic conditions that could be experienced on board ships; and
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.16 have the facilities to process augmentation data. When a QZSS receiver is
equipped to process augmentation data, performance standards for static and
dynamic accuracies should be less than 10 m (95%).
4 Integrity checking, failure warnings and status indication
4.1 QZSS receiver equipment should indicate whether the performance of QZSS is likely
to be outside the bounds of requirements for general navigation.
4.2 QZSS receiver equipment should, as a minimum:
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.1 provide a warning within 5 s of loss of position or if a new position
based on the information provided has not been calculated for more than 1 s.
Under such conditions, the last known position and the time of last valid
fix, with the explicit indication of the state allowing for no ambiguity,
should be output until normal operation is resumed; and
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.2 use receiver autonomous integrity monitoring to provide integrity
performance appropriate to the operation being undertaken.
5 Protection
Precautions should be taken to ensure that no permanent damage can result from an
accidental short circuit or grounding of the antenna or any of its input or output
connections or any of the QZSS receiver equipment inputs or outputs for a duration
of 5 min.