Ellipsoidal coordinates in cartography. <i>OA</i> is the semi-major axis; <i>OB</i> is the semi-minor axis; <i>F</i> and <i>F`</i> are the foci; <i>β</i> is the reduced latitude; <i>P</i> is a point on the Ellipsoid (e.g. the Earth); <i>Q</i> is a point on the surrounding sphere (of radius a).
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<span class="int-own-work" lang="en">Own work</span>. <a rel="nofollow" class="external text" href="https://github.com/mjhorvath/mike_illustrations">Download source code</a>.