lonlat_to_cart()

POINT3D * lonlat_to_cart	(	const double_t	raw_lon,
		const double_t	raw_lat
	)

Definition at line 208 of file geography_centroid.c.

References lwalloc(), POINT3D::x, POINT3D::y, and POINT3D::z.

Referenced by geography_centroid_from_wpoints().

{
    double_t lat, lon;
    double_t sin_lat;

    POINT3D* point = lwalloc(sizeof(POINT3D));;

    // prepare coordinate for trigonometric functions from [-90, 90] -> [0, pi]
    lat = (raw_lat + 90) / 180 * M_PI;

    // prepare coordinate for trigonometric functions from [-180, 180] -> [-pi, pi]
    lon = raw_lon / 180 * M_PI;

    /* calculate value only once */
    sin_lat = sinl(lat);

    /* convert to 3D cartesian coordinates */
    point->x = sin_lat * cosl(lon);
    point->y = sin_lat * sinl(lon);
    point->z = cosl(lat);

    return point;
}

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