OneMeterInDegrees(...)

( $degrees_ns, $degrees_ew ) = $index->OneMeterInDegrees( $latitude_radians );
Returns length in degrees of one meter (N/S and E/W) at given latitude

Values are approximate. The diameters are those for an oblate spheroid but the math assumes a sphere. As one approaches the poles these values get heavily distorted; code that uses them needs to take this into account.

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$latitude_radians - The latitude in radians

Return value
The return value is an array containing the width and height in degrees of one meter at the given latitude:
( degrees_ns, degrees_ew )