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Sep 18 - Crossing the Line

Position Report at 1400UTC Sunday 17th September 2006
Latitude: 01 32.4 N
Longitude: 030 31.0 W
Bearing: 25 T, 630 Nm from Recife
Destination 1: Montevideo
ETA at 11.5 knots is 07:22 on 27 September 2006
Total Distance Travelled: 3632
Total Steam Time: 310.2
Total Average Speed: 11.7
Wind: Direction SE, Force 5
Sea State: Moderate
Air Temp: 26.8 C Sea Temp: 28.2 C
Pressure: 1013.6 Tendency: Rising

By 0100 UTC on Monday 18th of September we should be crossing the Equator, on passage for Montevideo. Unfortunately for the ship's doctor, new Able Seaman, and cadets, a "crossing the line" ceremony is performed for those who have not done so at sea before, involving free haircuts for those willing and perhaps a short bath in the following;


Before sunrise on the 14th a spectacular electrical storm was witnessed by Second Officer David King and AB Kevin Holmes;

Picture by Dave King
Picture by Dave King

Blue skies and calm sea conditions have otherwise predominated, allowing plenty of opportunities for Cadet Andrew Gill to continue celestial navigation, including many twilight star sights. A snapshot of the Ship's SWATH Bathymetry system from 1000 UTC on the 17th reveals the topographic features of the Mid-Atlantic Ridge.

Screenshot by Jeremy Robst
Screenshot by Jeremy Robst

Mapping of the seabed outside national waters using SWATH Bathymetry involves sending out a sonar signal from the ship, which is reflected from the seafloor, the time delay before the signal returns allows the depth of the seafloor to be calculated. In order to allow for accuracy in data production gravitational sensors calculate the Ship's heave, pitch and roll, and these are accounted for in production of bathymetric data [Greek bathus deep metria measurer]. North of the Equator the Mid-Atlantic ridge runs to within a few hundred kilometres of the North Pole, to the South finishing at around 55degrees South. Evolving from diverging tectonic plates, the Mid-Atlantic Ridge's features are formed by plumes of magma arising from tension cracks the Earth's crust, explaining the volcanic activity in islands such as Iceland, which are situated along the ridge.