matvis.conversions.enu_to_az_za

matvis.conversions.enu_to_az_za(enu_e, enu_n, orientation='astropy', periodic_azimuth=True)[source]

Convert angle cosines in ENU coordinates into azimuth and zenith angle.

For a pointing vector in East-North-Up (ENU) coordinates vec{p}, the input arguments are enu_e = vec{p}.hat{e} and enu_n = vec{p}.hat{n}`, where ``hat{e} is a unit vector in ENU coordinates etc.

For a drift-scan telescope pointing at the zenith, the hat{e} direction is aligned with the U direction (in the UVW plane), which means that we can identify the direction cosines l = enu_e and m = enu_n.

Azimuth is oriented East of North, i.e. Az(N) = 0 deg, Az(E) = +90 deg in the astropy convention, and North of East, i.e. Az(N) = +90 deg, and Az(E) = 0 deg in the UVBeam convention.

Parameters:

  • enu_e (array_like) – Normalized angle cosine coordinates on the interval (-1, +1).

  • enu_n (array_like) – Normalized angle cosine coordinates on the interval (-1, +1).

  • orientation (str, optional) – Orientation convention used for the azimuth angle. The default is 'astropy', which uses an East of North convention (Az(N) = 0 deg, Az(E) = +90 deg). Alternatively, the 'uvbeam' convention uses North of East (Az(N) = +90 deg, Az(E) = 0 deg).

  • periodic_azimuth (bool, optional) – if True, constrain az to be betwee 0 and 2 * pi This avoids the issue that arctan2 outputs angles between -pi and pi while most CST beam formats store azimuths between 0 and 2pi which leads interpolation domain mismatches.

Returns:

az, za – Corresponding azimuth and zenith angles (in radians).

Return type:

array_like