OpenGL API Specifications
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Posted 13 July 2011 - 02:17 AM
Posted 13 July 2011 - 03:48 AM
Posted 13 July 2011 - 05:14 AM
Posted 17 July 2011 - 08:25 PM
The Earth is a planet, not a spheroid. Its precise mathematical model is rather complex.
For the most precise approximation of the mean sea level you should use geoid. The geoid is changing. It depends on the magnetic field of the Earth, but also depends on the Sun and the Moon. You can download some pretty precise geoid models of the Earth.
Less precise, but more common is the approximation that uses ellipsoid. WGS84 ellipsoid is used for GPS navigation and is very common these days.
The least accurate approximation of Earth curvature is a sphere. I have no idea what your visualization would serve for, but in 99.99% you will not see the difference between the shpere and WGS84 ellipsoid. You have noticed that there are differences between axis, but that difference is only 0.3%!!! The difference can be noticeable only when placing satellites high above the Earth, since calculated geographic position of the point beneath would significantly depend on the chosen approximation.
Also you would need same DEM data. For precise modeling you need several terabytes of data (both textures and DEM).
If the overlay is in a specific projection, you'll also need assistance of some GIS tool, or reprojecting library.
Posted 20 July 2011 - 10:59 AM
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