You can not use longitude lines to measure distance. Picture slicing an orange into sections - two straight cuts from the "poles" on a curved orange result in a section of peel pointy on each end and fat in the middle. But 071° East is near Kabul, Afghanistan.īecause they run from the North Pole to the South Pole, lines of longitude are not always the same distance apart. For example 071° West is a line running roughly through Cape Cod on the U.S. We designate lines of longitude West or East, relative to Greenwich England. We'll find this very convenient later on when we're measuring distances and plotting courses. If you have two latitude positions, you can estimate how far apart they are in a north/south direction. So every degree of latitude is always 60 nautical miles from the next. One minute of latitude is equal to one Nautical Mile. Latitude lines will be North or South of the equator and are always parallel to each other. Coordinates tell you where something is, then you can find it with your charts. With a road map, I can give you directions to that place by saying "From Post Road, take a left on King Street, then another left on Water street." But coming by water those directions are useless. ![]() If a longitude is only two digits (like the example), add a zero to the front of it to avoid confusion. This will be a little over 41° North of the equator, and a little more than 071° West of Greenwich, England. They are always in pairs, with latitude followed by longitude. There will also be a letter at the end to designate the hemisphere. 35☄3"25'), or with a decimal instead of Seconds (e.g. We express Geographic Coordinates as Degrees/Minutes/Seconds (e.g. Lines of longitude run from the north to the south start at 0° in Greenwich, England and run to 180° West and East. Lines of latitude range from 0° at the equator to 90° at the poles and run parallel to the equator. Geographic CoordinatesĬenturies ago cartographers devised Geographic Coordinate system to locate any place on the world. To understand how to do this, you need to understand how we refer to places in the world. Navigation is traveling a planned course from start to finish, using the chart to avoid obstacles and hazards. Eyeballing a lighthouse on land won't help you miss a shoal unless you know where the shoal is relative to your boat.Ī nautical chart shows things under water and describes the landmarks and references you can see. And the water may cover hazards like rocks and shoals that you need to avoid. And even if you can see landmarks, they won't help you if you can't identify them. If you get fog or it's night time or you're far out to sea, you have nothing to make one patch of blue look any different from another. When you can see land it's easier to figure where you are. No one will put a big rock in the middle of the highway that you won't see until you hit it.īut one patch of water looks a lot like another. If you're on Interstate 95 and you know the next exit number, you're good for figuring out where you are and how to get where you're going. On land you've got roads, which limit where you can drive and how much trouble you can get into. It shows you the expected lay of the land and gives references for finding your way to somewhere when don't know the path. Master Chart Navigation with One CourseĪ nautical chart is like a road map.Dead Reckoning - Pulling it all Together.This guide gives you all the basics on how to read a chart and use it to plot a safe course from where you are to where you want to go. If you're new to navigation this can overwhelm, especially if you're looking at a crowded electronic vector chart. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |