Performance Standard of Shipborne BeiDou Receiving Devices
1.1 BeiDou Navigation Satellite System is China’s independently developed and operated global navigation satellite system, which is compatible with other navigation satellite systems in the world. BeiDou is composed of three parts: the space section, the ground section and the user section.
The space section contains 5 geostationary earth orbit (GEO) satellites, 27 medium earth orbit (MEO) satellites and threeinclined geosynchronous orbit (IGSO) satellites. The GEO satellites locates at 58.75°E, 80°E, 110.5°E, 140°E and 160°E; the MEO satellites are evenly distributed on three orbital planes, with an orbit altitude of 21500 kilometers and a 55 degree dip angle. The orbit altitude of IGSO satellites is 36000 kilometers. The IGSO satellites are evenly distributed on three inclined geosynchronous planes, whose dip angle is 55 degree. The track of subsatellite point of the three IGSO overlaps on 118°E. The geometry configuration of this constellation makes sure that at least four satellites are visible to its global users. The positioning dilution of precision (PDOP) is less than or equal to 6. Every BeiDou satellite sends the public service signal B1I on waveband L using a carrier frequency of 1561.098 MHz. Signal B1I can provide the ranging code of public service, with the navigational message loaded on it. BeiDou uses CDMA to recognizesatellites.
1.2 BeiDou provides positioning, navigation and timing services, which are free of charge for its direct users. BeiDou receivers and receive and process the public service signal of BeiDou.
1.3 BeiDou receiver for shipping purpose on ships whose speed is lower than 70 knots should, not only fulfill the general requirements of the IMO A.694(17) resolution1, but also meet the minimum performance standards as listed below the item Performance Standard of Shipborne BeiDou Receiving Devices.
1.4 This standard contains only the basic requirements of positioning, COG,SOG and timing input for navigation or other functions. This standard does not contain the other possible calculation tools which the device might include, nor does it include the requirements of other systems whose input might be received by the BDS receiver.
2. The BeiDou receiving device
2.1 The BeiDou receiving device within this performance standard includes all the necessary parts and components which a receiver takes to function properly. BeiDou receiving device should contain at least the following parts:
.1 Antenna which can receive BeiDou signals
.2 BeiDou receiver and processor
.3 Software which can calculate and output the latitude and longitude location data
.4 Control interface of data output
.5 Position indicator or other output format in need
Note: If BeiDou is recognized as an approved part of the integrated navigation system (INS), then the requirement of 2.1.3, 2.1.4 and 2.1.5 can be provided within the INS.
2.2 In consideration of any possible occlusions on the ship, the design of the antenna should make sure that it’s in the visible position of the satellite.
3. The performance standard of BeiDou receiving devices
BeiDou receiving device should:
.1 Be able to receive and process the BeiDou signals of positioning, velocity measurement and timing. It should use the ionosphere model parameters sent by the BeiDou to correct the ionospheric delay.
.2 Provide longitude and latitude position information in measurement of degree, minute and one thousandth of one minute2.
.3 Provide time information based on UTC(NTSC)3.
.4 Have at least two output port, from which the position, UTC, COG, SOG and alarm information can be sent to other devices. The output location information should be based on WGS84 and should be consistent with the international standard4. UTC, , COG, SOG and alarm information output should be consistent with the requirements of 3.15 and 3.17.
.5 Make sure that the precision of the static positioning is within 25m (95%) horizontally and 30m (95%) vertically.
.6 Make sure that in the normal sea conditions and ship motion, the dynamic positioning accuracy of the receiving antenna should be equal to the precision of the static positioning5 required in .5 above.
.7 Provide position information by means of longitude and latitude in measurement of degree, minute and one thousandth of one minute. The resolution should be no less than 0.001 minute oflongitude and latitude.
.8 Be able to automatically choose suitable satellite signals to confirm the certain position, speed and time of the ship and should meet the requirement of accuracy and update rate.
.9 Be able to catch satellite signals whose electrical level of input signals are within a range between -130 dBm and -120 dBm. Once catching the satellite signals, and the electrical level of input signals are lower to -133 dBm, the receiver should continue to work normally.
.10 Be able to work normally and meet the requirements of A.694(17) Resolution under the normal interference condition.
.11 Be able to acquire position, speed and time information which meets the requirement within 12 minute , under the circumstance of no valid almanac data.
.12 Be able to acquire position, speed and time information which meets the requirement within 1 minute, with valid almanac data.
.13 Be able to acquire position, speed and time information which meets the requirement within 1 minute, should the service pause for 60 seconds or less.
.14 For conventional ships, generate a new position result at least once a second and output to displayer and digital interface6.
.15 Provide COG,SOG and UTC output, whose effectiveness tag should be in accordance with the effectiveness tag of position output. The accuracy requirement of COG and SOG should not be lower than the relevant performance standard of direction7, speed and distance measuring equipment(SDME), and should meet the accuracy standard under different dynamic situations a ship might encounter.
.16 At least provide one normally closed interlock, which should indicate the malfunction of BeiDou receiver.
.17 Should be equipped with bidirectional interface, which enables the alarm to be sent to the external system, and allow the auditory alarm from the BeiDou receiver to be confirmed by the external system. The interface should comply with the relevant international standards6.
.19 Have equipment to process difference BeiDou data (DBDS) according to ITU-R9 and RTCM standard, and indicate the receiving DBDS signals and if it is being used for positioning of the ship. If the ship is equipped with both BeiDou receiver and difference BeiDou receiver, the static and dynamic performance standard should be 10m (95%). (See 3.5 and 3.6)
4 Integrity test, malfunction alarm and status indication
4.1 BeiDou receiving equipment should also indicate if the BeiDou performance has gone beyond ocean, coast, near port, restricted waters and inland waterways. Such situation should be within the navigational requirement of A.1046(27) Resolution or the appendix 2 of A.915(22) Resolution and their subsequent amendments.
4.2 BeiDou receiver should at least
.1 Send alarm within 5 seconds should the location information is lost or does not receive result for new location information based on the BeiDou information after 1 second for conventional ships and 0.5 seconds for high speed ships. Under such condition, it should output the latest confirmed location and positioning time, and indicate the status clearly to avoid confusion, until the operation is back to normal.
.2 Can use the RAIM function of the receiver to make sure the integrity of the service information being provided.
.3 Provide self-test function of receiver.
Precautionary measures should be taken to make sure that the accidental malfunction of short circuit,antenna ground system, input and output link, or BeiDou receiver will not cause permanent damage to the equipment when the malfunction lasts less than 5 minutes.