feat(ephemeris): Import functions moved to caput (#72)

In radiocosmology/caput#269:
* `ch_util.ephemeris.sphdist` has been moved to `caput.interferometry.sphdist`
* `drift.telescope.cylbeam.rotate_ypr` has been moved to `caput.interferometry.rotate_ypr`

Updated `ch_util/holography.py` to use the caput version of `sphdist`
directly.

This removes the `driftscan` dependency.

ch_util/ephemeris.py

@@ -96,7 +96,6 @@
 
 - :py:meth:`galt_pointing_model_ha`
 - :py:meth:`galt_pointing_model_dec`
-- :py:meth:`sphdist`
 """
 
 from datetime import datetime
@@ -108,6 +107,7 @@
 
 import numpy as np
 
+from caput.interferometry import sphdist
 from caput.time import (
     unix_to_datetime,
     datetime_to_unix,
@@ -355,42 +355,6 @@ def utc_lst_to_mjd(datestring, lst, obs=chime):
     )
 
 
-def sphdist(long1, lat1, long2, lat2):
-    """
-    Return the angular distance between two coordinates.
-
-    Parameters
-    ----------
-
-    long1, lat1 : Skyfield Angle objects
-        longitude and latitude of the first coordinate. Each should be the
-        same length; can be one or longer.
-
-    long2, lat2 : Skyfield Angle objects
-        longitude and latitude of the second coordinate. Each should be the
-        same length. If long1, lat1 have length longer than 1, long2 and
-        lat2 should either have the same length as coordinate 1 or length 1.
-
-    Returns
-    -------
-    dist : Skyfield Angle object
-        angle between the two coordinates
-    """
-    from skyfield.positionlib import Angle
-
-    dsinb = np.sin((lat1.radians - lat2.radians) / 2.0) ** 2
-
-    dsinl = (
-        np.cos(lat1.radians)
-        * np.cos(lat2.radians)
-        * (np.sin((long1.radians - long2.radians) / 2.0)) ** 2
-    )
-
-    dist = np.arcsin(np.sqrt(dsinl + dsinb))
-
-    return Angle(radians=2 * dist)
-
-
 def solar_transit(start_time, end_time=None, obs=chime):
     """Find the Solar transits between two times for CHIME.
 
@@ -715,12 +679,10 @@ def hadec_to_bmxy(ha_cirs, dec_cirs):
         https://chime-frb-open-data.github.io/beam-model/#coordinate-conventions
     """
 
-    from caput.interferometry import sph_to_ground
+    from caput.interferometry import rotate_ypr, sph_to_ground
 
     from ch_util.tools import _CHIME_ROT
 
-    from drift.telescope.cylbeam import rotate_ypr
-
     # Convert CIRS coordinates to CHIME "ground fixed" XYZ coordinates,
     # which constitute a unit vector pointing towards the point of interest,
     # i.e., telescope cartesian unit-sphere coordinates.
@@ -773,12 +735,10 @@ def bmxy_to_hadec(bmx, bmy):
     """
     import warnings
 
-    from caput.interferometry import ground_to_sph
+    from caput.interferometry import rotate_ypr, ground_to_sph
 
     from ch_util.tools import _CHIME_ROT
 
-    from drift.telescope.cylbeam import rotate_ypr
-
     # Convert CHIME/FRB beam model XY position to spherical polar coordinates
     # with the pole towards almost-North and using CHIME's meridian as the prime
     # meridian. Note that the CHIME/FRB beam model X coordinate increases westward

ch_util/holography.py

@@ -257,7 +257,7 @@ def create_from_ant_logs(
         none
         """
 
-        from ch_util.ephemeris import sphdist
+        from caput.interferometry import sphdist
         from skyfield.positionlib import Angle
 
         ts = ephemeris.skyfield_wrapper.timescale

requirements.txt

@@ -12,4 +12,3 @@ bitshuffle
 caput[compression] @ git+https://github.com/radiocosmology/caput.git
 skyfield >= 1.10
 mpi4py
-driftscan @ git+https://github.com/radiocosmology/driftscan.git