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Thanks for taking the time to look into this, much appreciated!

The ellipse on the map is created by a longitude and latitude given in degrees.

Ex: (-103.0, 40.0)

Along with a minor/major axis represented in meters.

Ex: (semiMinorAxis : 400000.0, semiMajorAxis : 400000.0)

The map used, is a 3D Globe, provided by Cesium

With the information above, how would one calculate a list of coordinates which trace the rim of the ellipse?

Jared Smith
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  • That's a circle, silly – TonyK Jul 05 '17 at 14:00
  • @TonyK In this case yes, however, the major and minor axis will most likely not be equal. A Circle is a type of ellipse. – Jared Smith Jul 05 '17 at 14:01
  • seems to understand that the ellipses is created on a flat map, and is an ellipses on that map but not in 3D. Then you need to know what type of map it is, and how the ellipses is orientated in it to be able to answer. – G Cab Jul 05 '17 at 14:27
  • @GCab I am little confused by your comment. However, I do believe the type of map used in important, I'll add it now. Thank you. – Jared Smith Jul 05 '17 at 14:36
  • Yes, I know a circle is an ellipse. But it's a silly example to give, because it's such a special case. Drawing a circle is much easier than drawing an ellipse, especially on a curved surface. Even defining what it means to be an ellipse on a curved surface is not easy. – TonyK Jul 05 '17 at 15:35
  • One can define an "ellipse" on a closed surface as the locus of points whose sum of geodesic distances to two given foci is constant. On a sphere, if you orthogonal project an "ellipse" on sphere to the plane perpendicular to midpoint of the foci, the image will be an ordinary ellipse on that plane! (for a proof, see this). One possible solution for you problem is approximate the globe as a sphere, work out the equation for ellipse on the plane (perpendicular to your center location) and then project the points back to sphere/globe. – achille hui Jul 05 '17 at 18:00
  • @achillehui: the previous post you are referring to is very interesting! (+1). That's the case of an ellipses on the sphere: the post was originally speaking of A MAP, which to my understanding means a 2D map (obtained with some of the projections used since centuries). Now the post has been corrected to a 3D map : does it mean the sphere itself !? – G Cab Jul 05 '17 at 21:30
  • @GCab It depends on what accuracy the OP want. To the lowest approximation, the globe (aka the earth) is a sphere. However, for practical application these days, the globe is modeled as an oblate ellipsoid and latitude are quoted as geodetic latitude (instead of the much simpler geocentric one). Even if we approximate the "ellipse" by one of sphere, the conversion to the one on ellipsoid and geodetic latitude is not that trivial. – achille hui Jul 05 '17 at 22:29

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