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diff --git a/tde-i18n-en_GB/docs/tdeedu/kstars/geocoords.docbook b/tde-i18n-en_GB/docs/tdeedu/kstars/geocoords.docbook new file mode 100644 index 00000000000..5f8d87bf8a7 --- /dev/null +++ b/tde-i18n-en_GB/docs/tdeedu/kstars/geocoords.docbook @@ -0,0 +1,66 @@ +<sect1 id="ai-geocoords"> +<sect1info> +<author +><firstname +>Jason</firstname +> <surname +>Harris</surname +> </author> +</sect1info> +<title +>Geographic Coordinates</title> +<indexterm +><primary +>Geographic Coordinate System</primary +></indexterm> +<indexterm +><primary +>Longitude</primary +><see +>Geographic Coordinate System</see +></indexterm> +<indexterm +><primary +>Latitude</primary +><see +>Geographic Coordinate System</see +></indexterm> +<para +>Locations on Earth can be specified using a spherical coordinate system. The geographic (<quote +>earth-mapping</quote +>) coordinate system is aligned with the spin axis of the Earth. It defines two angles measured from the centre of the Earth. One angle, called the <firstterm +>Latitude</firstterm +>, measures the angle between any point and the Equator. The other angle, called the <firstterm +>Longitude</firstterm +>, measures the angle <emphasis +>along</emphasis +> the Equator from an arbitrary point on the Earth (Greenwich, England is the accepted zero-longitude point in most modern societies). </para +><para +>By combining these two angles, any location on Earth can be specified. For example, Baltimore, Maryland (USA) has a latitude of 39.3 degrees North, and a longitude of 76.6 degrees West. So, a vector drawn from the centre of the Earth to a point 39.3 degrees above the Equator and 76.6 degrees west of Greenwich, England will pass through Baltimore. </para +><para +>The Equator is obviously an important part of this coordinate system; it represents the <emphasis +>zeropoint</emphasis +> of the latitude angle, and the halfway point between the poles. The Equator is the <firstterm +>Fundamental Plane</firstterm +> of the geographic coordinate system. <link linkend="ai-skycoords" +>All Spherical Coordinate Systems</link +> define such a Fundamental Plane. </para +><para +>Lines of constant Latitude are called <firstterm +>Parallels</firstterm +>. They trace circles on the surface of the Earth, but the only parallel that is a <link linkend="ai-greatcircle" +>Great Circle</link +> is the Equator (Latitude=0 degrees). Lines of constant Longitude are called <firstterm +>Meridians</firstterm +>. The Meridian passing through Greenwich is the <firstterm +>Prime Meridian</firstterm +> (longitude=0 degrees). Unlike Parallels, all Meridians are great circles, and Meridians are not parallel: they intersect at the north and south poles. </para> +<tip> +<para +>Exercise:</para> +<para +>What is the longitude of the North Pole? Its latitude is 90 degrees North. </para> +<para +>This is a trick question. The Longitude is meaningless at the north pole (and the south pole too). It has all longitudes at the same time. </para> +</tip> +</sect1> |