Helicopter ship board landing system

A system for positioning an aircraft relative to a designated location on an ocean-going vessel, the system comprising:

• A. on the vessel, a navigation unit including:
• 1. a first GPS receiver configured to receive and process signals received over a first GPS antenna, thereby to provide periodic position data;
• 2. a first inertial navigation unit (INU) configured to received periodically updated data generated by said first GPS receiver at a rate that minimizes INU error, relating to the position of the vessel;
• 3. a transmitter that transmits over a wireless link to an associated aircraft, the position data generated by the first GPS receiver and the first INU;
• and
• B. in the aircraft, a navigation unit including:
• 1 a second GPS receiver configured for receiving and processing GPS signals received over a second GPS antenna,
• 2. a second INU having an output that is updated in accordance with periodically updated data that are based on updated data from the first INU and an RTK moving baseline vector determined using data from the first and second GPS receivers, the updated data from the first INU and the RTK moving baseline vector being associated with times at which measurements are available at the GPS receivers,
• 3. a receiver adapted to receive signals transmitted over the wireless link by the transmitter in the navigation unit on the vessel,
• 4. an RTK arrangement configured to process the GPS data to generate the RTK moving baseline vector from the second antenna to the first antenna, and said RTK arrangement being further configured for differencing a post-update remote position at the aircraft based on second INS data with a post-update base station position on the ship based on first INS data to produce a correction vector and subtracting the correction vector from the RTK moving baseline vector to obtain a post-update inertial position correction, and
• 5. the aircraft INU being further configured to update its output with said post-update inertial position correction and to compute a position vector of high accuracy to guide the aircraft for landing at a designated location on the vessel.

A system comprising

• on a ship, a first navigation unit comprising:
• a first satellite signal receiver that processes signals received by a first antenna;
• a first inertial navigation unit (INU) that is updated using data that are provided by the first satellite signal receiver and associated with a given time tag;
• a transmitter for transmitting satellite signal and INU information;
• on an aircraft, a second navigation unit comprising:
• a second satellite signal receiver that process signals received by a second antenna;
• an RTK sub-system configured to use data from the first and second satellite receivers to determine an RTK moving baseline vector between the first antenna and the second antenna, the RTK moving base line vector being associated with the given time tag;
• a second INU that is periodically updated based on the RTK moving baseline vector and the updated data from the first INU;
• and
• one or more processors configured to produce a post-update inertial position correction based a correction calculated for the RTK moving baseline vector using post-update data from the first and second INUs, and to update the output position of the second navigation unit with the post-update inertial position correction to restore relative accuracy between the shipboard and the aircraft navigation units and produce a corrected relative aircraft position.

A navigation system consisting of

• a ship navigation subsystem including
• a first GPS receiver and associated first GPS antenna, the first GPS receiver periodically determining GPS position data relating to the first GPS antenna;
• a first INU configured to use the position data determined by the first GPS receiver to update inertial positions and between updates determines post update inertial positions based on INU sensor data;
• a transmitter that transmits the GPS position data and the inertial positions to a remote navigation subsystem;
• the remote navigation subsystem including
• a second GPS receiver and associated second GPS antenna, the second GPS receiver periodically determining GPS position data relating to the second GPS antenna;
• an RTK processor configured to use the GPS position data determined by the first and second GPS receivers to determine enhanced positions of the second GPS antenna and associated baseline vectors between the first and second GPS antennas;
• a second INU configured to use the enhanced positions to update inertial positions and between updates determine post-update inertial positions based on INU sensor data;
• the RTK processor further configured to determine a baseline correction vector based on the post-update inertial positions of the first and second GPS antennas, the RTK processor configured to use the baseline correction vector to correct the post-update positions determined by the second INU.