heyoka.model.get_egm2008_CS

heyoka.model.get_egm2008_CS() → numpy.ndarray

Get the harmonic coefficients of the EGM2008 model.

Added in version 7.12.0.

This function will return the set of normalised \(\bar{C}_{nm}\) and \(\bar{S}_{nm}\) harmonic coefficients of the EGM2008 geopotential model.

The coefficients are returned as a read-only (N, 2) array of double-precision values, where each row is a [C, S] pair and the rows are ordered by degree and then by order. See the sh_gravity_pot() function for a detailed description of the layout.

Note

Consistently with the published EGM2008 coefficients, this function will return [C, S] pairs starting from the harmonic degree \(n=2\) (and not \(n=0\)). In the EGM2008 model \(\bar{C}_{0,0}=1\), while all the remaining coefficients of degree less than 2 are zero.

As a consequence, the returned array is not directly in the format expected by the sh_coefficients argument of sh_gravity_pot() and sh_gravity_acc(), which begins at \(n=0\). To use these coefficients with those functions, prepend the three lower-degree pairs [1.0, 0.0], [0.0, 0.0] and [0.0, 0.0] (corresponding to \((n,m)\) indices \((0,0)\), \((1,0)\) and \((1,1)\)).

Returns:

a read-only (N, 2) array of normalised [C, S] harmonic coefficient pairs.