FREJVALL PER (SE)
| WO1993017334A1 | 1993-09-02 | |||
| WO2009029129A1 | 2009-03-05 |
| US20110076904A1 | 2011-03-31 |
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"Types of Automatic Identification Systems", US COAST GUARD NAVIGATION CENTER, 7 June 2011 (2011-06-07), Retrieved from the Internet
PRINSENBERG S J ET AL.: "Pack ice stress and convergence measurements by satellite- tracked ice beacons", OCEANS '97. MTS/IEEE CONFERENCE PROCEEDINGS HALIFAX, vol. 2, 6 October 1997 (1997-10-06), NS, CANADA, pages 1283 - 1289
| Claims 1. Method for determining a position of an ice buoy (1), which boy is provided with a GPS device (11) and a transmit- ter (9) for transmitting its position and identity to a receiving party, such as a ship or vessel, which is provided with a navigation system (6) that is adapted to receive sig¬ nals according to AIS standard, c h a r a c t e r i s e d i n, that said GPS device (9) is arranged to produce unfil- tered position information as regards so called Speed filtering, in that the unfiltered position information is caused to be transmitted by the transmitter (9) to a base station onboard a ship or vessel, in that a receiver (3) of the base station is connected to a converter (5) arranged to covert the received position information to a signal protocol ac¬ cording to AIS (Automatic Identification System) and in that the converter (5) in caused to feed the converted signal into said navigation system (6) . 2. Method according to claim 1, c h a r a c t e r i s e d i n, that the transmitter (9) is caused to transmit the posi¬ tion of the buoy (1) with a predetermined time frequency regardless of the speed of movement of the buoy. 3. Method according to claim 2, c h a r a c t e r i s e d i n, that the transmitter (9) is caused to transmit the posi¬ tion of the buoy (1) at time intervals no longer than five minutes . 4. Method according to claim 1, 2 or 3, c h a r a c ¬ t e r i s e d i n, that said transmitter (9) is caused to transmit on the 400 or 800 MHz band. 5. Method according to claim 1, 2, 3 or 4, c h a r a c ¬ t e r i s e d i n, that the converted signal is caused to be a signal according to NMEA standard. 6. System for determining a position of an ice buoy (1), which boy is provided with a GPS device (11) and a transmit¬ ter (9) for transmitting its position and identity to a receiving party, such as a ship or vessel, which is provided with navigation system (6) that is adapted to receive signals according to AIS standard, c h a r a c t e r i s e d i n, that said GPS device (11) is arranged to produce an unfil- tered position information as regards so called Speed filter¬ ing, in that the transmitter (9) is arranged to transmit to a base station onboard a ship or vessel, in that a receiver (3) of the base station is connected to a converter (5) arranged to covert the received position information to a signal pro¬ tocol according to AIS and in that the converter is arranged to feed the converted signal into said navigation system (6) . 7. System according to claim 6, c h a r a c t e r i s e d i n, that the transmitter (9) is arranged to transmit the position of the buoy (1) with a predetermined time frequency regardless of the speed of movement of the buoy. 8. System according to claim 7, c h a r a c t e r i s e d i n, that the transmitter (9) is caused to transmit the posi¬ tion of the buoy (1) at time intervals no longer than five minutes . 9. System according to claim 6, 7 or 8, c h a r a c ¬ t e r i s e d i n, that said transmitter (9) is arranged to transmit on the 400 or 800 MHz band. 10. System according to claim 6, 7, 8 or 9, c h a r a c ¬ t e r i s e d i n, that the converted signal is a signal according to NMEA standard. |
The present invention refers to a method and apparatus for determining a position of an ice buoy.
Ice buoys are used in the Artie area for reporting ice movements on a small or a large scale. The ice buoys are deployed on the ice. Each buoy is provided with equipment to receive GPS signals to determine the position of the buoy and a transmitter arranged to transmit the position of the buoy to a base station via AIS (Automatic Identification System) or through satellite networks. The AIS system is a standardised system used worldwide by ships informing a ship of neighbouring ships and their identity. There is a problem with both of these methods since they yield inadequate accuracy for ice drift calculations and are very expensive.
The problem with an inadequate accuracy is due to that the AIS system transmits the position of the buoy depending on the speed of the movement of the buoy. Since the ice moves slowly, such as 0.1 to 1 knot, the transmitter will send a new position after for example 50 meters from the latest position. Ice that moves may move in spirals and other patterns and fairly sharp turns, where the extension of such a spiral or turn is less than 50 meters. This gives that when making mathematical prognosis for the movement of the ice, the input values for different parameters such as how the ice actually moves, the buoys yield incorrect positions on how the ice actually has moved, which incorrect values will be used as input values. For example information about the movements of the ice is used to predict where icebreakers shall break ice in relation to the position of a ship for offshore drilling.
Ice movements prognoses are made and are fed into among others the navigation system of a ship. This enables the crew to see on a screen how the ice has moved and how it is expected to move. Hereby the crew can move the ship to a good position relative to the ice.
The navigation systems of ships are designed to mark the position of a ship or a buoy on a screen on the bridge of the ship according to the MS standard.
Buoys are normally deployed by a person placing the buoy on the ice. This is costly and time consuming since a ship or helicopter must manoeuvre to the location where the buoy shall be placed. Normally at least 3 to 7 buoys have to be deployed in order to make it possible to make a prognosis of the movements of the ice.
The present invention solves the problem related to that the AIS system transmits the position of the buoy depending on the speed of the movement of the buoy.
Thus the present invention refers to a method for determining a position of an ice buoy, which boy is provided with a GPS device and a transmitter for transmitting its position and identity to a receiving party, such as a ship or vessel, which is provided with navigation system that is adapted to receive signals according to AIS standard, . The invention is characterized in, that said GPS device is arranged to produce unfiltered position information as regards so called Speed filtering, in that the unfiltered position information is caused to be transmitted by the transmitter to a base station onboard a ship or vessel, in that a receiver of the base station is connected to a converter arranged to covert the received position information to a signal protocol according to AIS (Automatic Identification System) and in that the converter in caused to feed the converted signal into said navigation system. Further the invention refers to a system of the kind and with essentially with the features according to claim 6.
Below the present invention is described in greater detail together with an exemplifying embodiment of the invention, where
- Figure 1 is a blockdiagram
- Figure 2 shows a buoy.
The present invention is a method for determining a position of an ice buoy 1, which boy is provided with a GPS device and a transmitter for transmitting its position and identity to a receiving party, such as a ship, which is provided with navigation system that is adapted to receive signals according to AIS standard.
According to the invention said GPS device is located in the buoy 1 and is arranged to produce unfiltered position information as regards so called Speed filtering. The unfiltered position information is caused to be transmitted by the transmitter located in the buoy 1 and having an antenna 2 to a base station provided with a receiver 3 with an antenna 4 onboard a ship or vessel. The receiver 3 of the base station is connected to a converter 5 arranged to covert the received position information to a signal protocol according to AIS (Automatic Identification System) . Thereafter the converter 5 in caused to feed the converted signal into said navigation system 6 of the ship or vessel .
The converter 5 can be a computer or it could be integrated in the navigation system 6.
The buoy 1 thus comprises a housing 7 which comprises a power package 8, said transmitter 9 and an electronic package 10 and a GPS receiver 11 and antenna. The buoy 1 is enlongated and has in one of its end a metal barb 17 suitable for putting the buoy 1 in the ice so that the buoy 1 is sitting in the ice in an upright position.
The power package 8 consists of a battery pack of Lithium-Ion or low temperature Lithium batteries or any other suitable battery that operate at low temperatures.
The transmitter 9 has an output power of 1 to 10 W. The transmitter uses a direct digital modulation technique. Demo- dulation is handled by said receiver having digital signal processors .
According to a preferred embodiment of the present invention the transmitter operates at the 400 or 800 MHz band.
The electronic package is arranged to handle and create the signal to be transmitted by the transmitter 9. Said signal contains the coordinates of the buoy created by means of a proprietary signal protocol. The electronic package is arranged to receive the GPS signals, assemble data packages and to control a transmitter section in order to deliver messages regarding the position.
The electronic package is designed to deliver a position two times a minute.
According to a very important embodiment of the invention the transmitter 9 is caused to transmit the position of the buoy 1 with a predetermined time frequency regardless of the speed of movement of the buoy 1.
According to a further embodiment the transmitter 9 is caused to transmit the position of the buoy 1 at time intervals no longer than five minutes. This gives that the position of a buoy is collected such that all movements such as spirals, sharp turns etc. of the buoy will be recorded.
The received GPS signal contains a clock signal giving actual time. Each of the buoys 1 is programmed to transmit its position within a time window when no other buoy is transmitting its position.
The above mentioned converted signal which is fed by the converter 3 to the navigation system of the ship or vessel is caused to be a signal according to NMEA standard. This means that the position of the buoys 1 will appear with their respective identity on a screen 12 on the bridge of the ship or vessel as if the position information had been transmitted according to the AIS standard. In Figure 1 the stars 13, 14 mark two respective buoys 1. The navigation system 6 may also display the movements of the respective buoys during a cer- tain time back. In Figure 1 the curves 15, 16 illustrates the movements of the buoys 1 and thereby the ice from a certain time back in time.
Above several embodiments of the invention has been described. However, the present invention can be varied. For example the buoy may be designed in another way.
Thus, the present invention shall not be restricted to the above described embodiments, but can be varied within the scope of the claims.