Convert geocentric geodetic coordinates into geocentric Cartesian coordinates about boule HOT 7 CLOSED

@birocoles you’re right and we have to be careful with the wording of things. We can probably focus only on the geocentric ellipsoids for now. To avoid confusion it might be best to leave the word "geocentric" for the spherical coordinates. Then we can discriminate the elipsoids that are non-geocentric since they will be an exception.

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@birocoles was this meant for Boule? 😆

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@birocoles this would be great to have here 👍 It should be a method in boule.Ellipsoid.

To clarify, do you mean geocentric spherical to Cartesian? The geodetic coordinates aren't really geocentric, right?

Either way, the method should look similar to the current geodetic_to_spherical (and its inverse).

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Hi @leouieda ,

There is a vast and complicated literature about coordinate systems used in geodesy (e.g., Soler, 1976; Soler & Hothem, 1988; Jekeli, 2012). I think we need to define a common nomenclature here.

Geodetic coordinates are defined by using a reference ellipsoid. Some ellipsoids are geocentric (e.g., NAD83, WGS84) and some ellipsoids are non-geocentric (e.g., NAD27).

The common formulas for transforming geodetic coordinates into geocentric Cartesian coordinates presume that the origin of the Cartesian system coincides with the center of the reference ellipsoid (Jekeli, 2012, subsection 2.1.5).

I will try to put all these together to make things as clear as possible in Boule.

Soler, T. (1976). On differential transformations between Cartesian and curvilinear (geodetic) coordinates, Depart. of Geodetic Science, Report no. 236. The Ohio State University, Columbus, Ohio. url: https://www.ngs.noaa.gov/web/data_imagery/CORS/Articles/

Soler, T. & L.D. Hothem (1988). Coordinate systems used in geodesy: Basic definitions and concepts, J. Surv. Eng., ASCE, 114(2), 84-97. url: https://www.ngs.noaa.gov/web/data_imagery/CORS/Articles/

Jekeli, C. (2012). Geometric Reference Systems in Geodesy, The Ohio State University. url: http://hdl.handle.net/1811/51274

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@birocoles have a look at this discussion geospace-code/pymap3d#24 This package might already have what we need.

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Closing since this is available in pymap3d.geodetic2ecef and its inverse. As of #121 we can pass Boule ellipsoids to pymap3d functions so there is no need to re-implement this here.

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