Click on the link below to watch a fascinating and accurate picture of the actual track of Costa Concordia as it approached Point di Castellari about 20:35. You can see that they were steering directly toward Giglio Island at 15.5 knots. As they neared the point, the ship began to execute a nearly 60 degree turn to the north. Although the Rate of Turn (ROT) data did not seem to be working, it is interesting to watch the turn develop, at the last minute, apparently with hard over helm that caused a significant "advance" toward the rocks on the Point. (Advance is the track a ship continues to maintain sideways when a hard turn is executed. ((A skid)) It is exacerbated by full rudder and a high rate of speed).
After striking the rocks, the ship continued to lose speed until it seemed to be almost dead in the water just north of its final resting place. It appears that there was some power available to make an almost 180 degree turn and slowly thrust the vessel sideways toward the beach, possibly aided by wind or current. . Note the differences between the compass heading (HDG) and the Course Over Ground (COG).
This data was obtained from the Concordia's AIS transmitter, a device required to be carried on all large ships, that transmits the vessel's position, as determined by GPS, to other vessels and shore monitors by means of VHF radio. The abbreviated data shown in the square box is just a small part of all the information that is available. The position data can be plotted on a navigation chart showing time intervals as seen here in the picture.
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