초록 ▼

In a satellite navigation system for an ocean vessel, a major source of error is unknown ocean currents when the navigation is done by dead-reckoning with respect to the waters. The present method for determining and correcting for ocean navigation error which is caused by unknown ocean currents pro

In a satellite navigation system for an ocean vessel, a major source of error is unknown ocean currents when the navigation is done by dead-reckoning with respect to the waters. The present method for determining and correcting for ocean navigation error which is caused by unknown ocean currents provides a highly accurate position of the vessel with respect to the earth. The position error reflects not only the difference between a dead-reckoned position and a satellite fix position which up-dates the dead-reckoned position but also accounts for the motion of the vessel due to the ocean currents during the time between the satellite lock-on and the actual error computation and correction.

대표청구항 ▼

In a system having a satellite fix position determining means and a dead-reckoning means for continuously estimating position between satellite fixes, a method for correcting ocean vessel navigation errors due to essentially constant water currents, comprising the steps of: periodically locking on t

In a system having a satellite fix position determining means and a dead-reckoning means for continuously estimating position between satellite fixes, a method for correcting ocean vessel navigation errors due to essentially constant water currents, comprising the steps of: periodically locking on to a satellite and determining present vessel position in latitude (fF2) and longitude (lF2) using satellite fixes at lock-on, comparing satellite fix latitude (fF2) and longitude (lF2) with dead-reckoned latitude (fDR) and longitude (lDR), respectively, at the time of fix to yield update corrections in latitude (fu) and in longitude (lu), defining differential functions (Aij) which relate respective changes in current satellite fix position in latitude (fF2) and longitude (lF2) to respective changes in velocity in the north (vN) and east (vE) directions, partially predicting satellite fix errors in latitude (fE) and longitude (lE) at current and previous satellite updates as a function of the velocity changes (vN and vE) and the differential functions (Aij), determining the values for the differential functions Aij, comprising the steps of introducing known velocity errors in the north and east directions and measuring variations in satellite fix latitude (fF2) and longitude (lF2) positions resulting from the introduced known velocity errors, measuring the time (T) between satellite updates, and determining the velocity north and velocity east errors (vN and vE) as a function of: time between satellite updates, update corrections (fu and lu), and differential functions (Aij).