Thursday, November 26, 2009

Technical Jargon Day

Hi All,
Explanation of todays events for the technical and none technical followers and everyone who is watching my progress.
Today at 0600hrs GMT -1 hr UTC behind UK pos 14,27.05N 027,51.64W, I started my 'Great Circle Sailing route' to waypoint 6 (Barbados) on the map.
this, wind permiting, will be a straight line for me from 0600hr position to that waypoint. It will save me some miles and give me a slightly quicker passage time. Explanation of GCS for those who are chalanged in this dept. this includes me, is.......
Imagine an orange with 24 segments in it (after you peeled it of course) the top and bottom would be planet earth north and south poles. The segments widest part the equator. each segment going north or south gets narrower toward the point they all meet, these are lines of longditude. To plot accurate positions on a chart, these lines are made parallel, so drawing a straight line anywhere on a chart, other than on the equator east west, or north and south, is impossibe, as every second of latitude which = 1 nautical mile at the equator, (slices of orange the bar person puts into your drink) gets bigger (thicker) the further north or south you travel. (dont think that applies to bar persons orange slice size though).
They have special charts were all these lines are drawn as is, and they do get narrow! this is were I draw my straight line; Were this line crosses each line of longditude I plot that position on my passage chart, I then join the dots all up with staight lines, and bingo! I get a curved line on my chart, giving me the course to steer.
Now cut the orange in two top to bottom, leaving 12 segments in each half. Each segment adds up to 15 deg (180 divided by 15 = 12 hours of time) of longditude. Were you halfed it, on the equator of that half, one side is Grenwich. The other 'the international date line' +/- 12 hours at 180 deg. Each 15 deg is 1 hour of 'Time' so as I am going west, every 15 deg, I will put my clocks back 1 hour, I put them back yesterday 1 hr and today 1 hour at 0700hrs to agree with my present position on the planets surface, So I am now -2 UTC. 2 hours behind you lot in the UK. I will put them back again when I reach 45 deg longditude. Barbados is just short of 60 deg long another hour there, Barbados being -4 UTC.
Whew, Hope you got that. If you didn't ask Tack in the Bull, he will tell it better than me. (sorry Tack)
Roy

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