Geography 2122A/B Chapter Notes - Chapter 1: Spherical Coordinate System, United States Geological Survey, North American Datum
25 Oct 2013
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Oldest way is by using instruments: for observing positions of celestial bodies, technique: establish celestial lines of position (east-west, north- south) by comparing the predicted positions of celestial bodies with their observed positions. Sextant tool used to measure the angle of a celestial body above the earth"s horizon: nautical navigators used to find their way using the moon, planets and stars, including our sun. In southern hemisphere, latitude is harder to find because four stars are used to interpolate due south as there is no equivalent to polaris over the. Navigators use a small constellation called crux australis (the. The prime meridian at 0 degree longitude passes through greenwich, Therefore, each hour difference between your time and that at. Greenwich, called greenwich mean time or gmt, is roughly equivalent to. 15 degree of longitude from greenwich: to determine geodetic longitude, compare you local time with. Greenwich mean time and multiply by 15 degree of longitude for each hour of difference.
