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<em>d.geodesic</em> displays a geodesic line in the active frame on the user's
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graphics monitor. This is also known as the great circle line and traces the
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shortest distance between two user-specified points on the curved surface of
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a longitude/latitude data set. The two coordinate locations named must fall
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within the boundaries of the user's current geographic region.
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By default black line color and red text color will be used.
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By indicating the starting and ending coordinates
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of the geodesic, the line and its length (by default in meters) are displayed to
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the graphical output. If the text color is set to <em>none</em>,
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the great circle distance is not displayed.
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A geodesic line if shown over the political map of the world
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(demolocation dataset):
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<div class="code"><pre>
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g.region vector=country_boundaries -p
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d.vect country_boundaries type=area
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# show additionally a 20 degree grid
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d.geodesic coordinates=55:58W,33:18S,26:43E,60:37N \
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line_color=yellow text_color=red units=kilometers
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<img src="d_geodesic.png" border=1><br>
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<i>Geodesic line (great circle line)</i>
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This program works only in GRASS locations with longitude/latitude
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<a href="d.rhumbline.html">d.rhumbline</a>,
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<a href="d.grid.html">d.grid</a>
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Michael Shapiro, U.S. Army Construction Engineering Research Laboratory
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<p><i>Last changed: $Date: 2014-12-28 14:30:25 +0100 (Sun, 28 Dec 2014) $</i>