# Excercise 2 - Exercise Two 1,Read the reference books and...

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Exercise Two 1,Read the reference books, and explain the methods can be used to measure astronomic latitude, astronomic longitude. Since the positions on many stars have been measured by astronomers, basically be measuring how far they are away from the rotation axis. So when a star whose coordinates are known, the elevation angle of the star at its highest or lower point can be used to determine astronomic latitude. There is a very good star to use and this is the sun. Its declination changes through out the year because of the tilt of the Earth’s equatorial plane There is however two special times when the sun is very easy to use: The fall and spring equinoxes. The fall equinox occurs on Sep 23. At the equinoxes, the sun is in the equator plane of the earth and so its declination is zero. A simple measure of the elevation angle to the Sun at its highest elevation is a direct measure of the latitude (90 minus the elevation angle is the latitude). To determine longitude, we need know the time when the star crosses the meridian. The

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## This note was uploaded on 03/22/2010 for the course GEOMATICS LSGI taught by Professor Kady during the Spring '07 term at Hong Kong Shue Yan.

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Excercise 2 - Exercise Two 1,Read the reference books and...

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