helper_functions.py 文件源码

def _lonlat_from_geos_angle(x, y, geos_area):
    """Get lons and lats from x, y in projection coordinates."""
    h = (geos_area.proj_dict['h'] + geos_area.proj_dict['a']) / 1000
    b__ = (geos_area.proj_dict['a'] / geos_area.proj_dict['b']) ** 2

    sd = np.sqrt((h * np.cos(x) * np.cos(y)) ** 2 -
                 (np.cos(y)**2 + b__ * np.sin(y)**2) *
                 (h**2 - (geos_area.proj_dict['a'] / 1000)**2))
    #sd = 0

    sn = (h * np.cos(x) * np.cos(y) - sd) / (np.cos(y)**2 + b__ * np.sin(y)**2)
    s1 = h - sn * np.cos(x) * np.cos(y)
    s2 = sn * np.sin(x) * np.cos(y)
    s3 = -sn * np.sin(y)
    sxy = np.sqrt(s1**2 + s2**2)

    lons = np.rad2deg(np.arctan2(s2, s1)) + geos_area.proj_dict.get('lon_0', 0)
    lats = np.rad2deg(-np.arctan2(b__ * s3, sxy))

    return lons, lats