Day Skipper theory - Charts the magic of the maps

[@newfie8]

Great Job. Sometimes people don’t realize how important people like you are!

[@waldek32]

finally clear english and visible explanation . greetings from Poland

[@bluecap5434]

thanks for the very useful information you kindly provide. looking forward to hearing soon.

[@faisalsaaid634]

Great Explanation ., Thank you From Yemen

[@macgyver6115]

Thank you for your time, to make these excellent videos

[@Brian.Heffernan]

Great little video 👌

[@Learn2Sail]

Glad you enjoyed. Cheers

[@eddsummat2191]

So in reading charts is the opposite way to reading an OS map (along the corridore and up the stairs) ie would be long the lat no for a grid reference

[@Learn2Sail]

Yup. I guess it is. Latitude first, then longitude. On the bottom or horizontal scale

[@markwilson8632]

She has to come across before you can get up her is the way I was taught. Military but using mills rather than degrees.

[@LexLuthor1234]

Grazie! :)

[@robertprecious2614]

I am about to do my day skipper course and what I would find helpful is a priority list of what calcs need to be done in the correct order so as not to forget anything?

[@Learn2Sail]

Each subject will be different, so best learn as you go along

[@lukasvandewiel860]

Perhaps add that longitudinal minutes of arc are nautical miles only at the equator, and that they get smaller as you move closer to the poles, because the circles around the planet become smaller. (Genuine question: Do we take into account that the Earth is better approximated by an ellipsoid than by a perfect sphere, because of its rotation, or is that effect too insignificant?)

[@Learn2Sail]

Thanks for the comment, but the video is geared at those just starting out in learning charts, too much information to start with would swamp them. These things get mentioned in the classroom. Thanks for your input.

[@lukasvandewiel860]

@@Learn2Sail From your youtube marketing there is a reasonable chance that we will see each next summer during a Competent Crew course. ;-) I will prepare by studying the navigation theory by the light of the Christmas tree. :-)

[@bigglyguy8429]

I can understand how the longitude lines will change across the curvature of the Earth, but I thought the parallels were called that because they are equally spaced?

[@lukasvandewiel860]

​@@bigglyguy8429 The planes through parallels are all indeed parallel as you say. If you stand on a parallel, and draw and imaginary line from your feet to the center of the earth, the angle that line makes with the equatorial plane is the value of the parallel. If the earth were a perfect sphere, the arc distance from parallel to parallel would be the same from equator to pole. However, the centrifugal force due to rotation of the earth turns our planet into an ellipsoid. If you are standing at sea level at the equator, you are standing about 6378 km from the center of the earth. At the poles that is just 6357 km. 21 km difference. This causes the parallels near the equator to be further apart than at the poles. A degree latitude at the equator is very close to 2 * pi * 6378 / 360 = 111.317 km and a degree latitude at the poles is very close to 2 * pi * 6357 / 360 = 110.951 km. Almost 400 meter difference. Might be small enough to ignore on the vast ocean, or it might not be.

[@bigglyguy8429]

@@lukasvandewiel860 Thanks for that. It's interesting to know. Is this accounted for on charts?

[@harbourdogNL]

Thank you.

[@brooklynnunya1179]

Cool

[@debbiebebington9803]

very nice but the bleeps in the background is annoying

[@jimmybrokos4610]

👍🏼👍🏼👍🏼