def shift_vis_to_image(vis: Visibility, im: Image, tangent: bool = True, inverse: bool = False) -> Visibility:
"""Shift visibility to the FFT phase centre of the image in place
:param vis: Visibility data
:param im: Image model used to determine phase centre
:param tangent: Is the shift purely on the tangent plane True|False
:param inverse: Do the inverse operation True|False
:return: visibility with phase shift applied and phasecentre updated
"""
assert isinstance(vis, Visibility), "vis is not a Visibility: %r" % vis
nchan, npol, ny, nx = im.data.shape
# Convert the FFT definition of the phase center to world coordinates (1 relative)
# This is the only place in ARL where the relationship between the image and visibility
# frames is defined.
image_phasecentre = pixel_to_skycoord(nx // 2 + 1, ny // 2 + 1, im.wcs, origin=1)
if vis.phasecentre.separation(image_phasecentre).rad > 1e-15:
if inverse:
log.debug("shift_vis_from_image: shifting phasecentre from image phase centre %s to visibility phasecentre "
"%s" % (image_phasecentre, vis.phasecentre))
else:
log.debug("shift_vis_from_image: shifting phasecentre from vis phasecentre %s to image phasecentre %s" %
(vis.phasecentre, image_phasecentre))
vis = phaserotate_visibility(vis, image_phasecentre, tangent=tangent, inverse=inverse)
vis.phasecentre = im.phasecentre
assert isinstance(vis, Visibility), "after phase_rotation, vis is not a Visibility"
return vis
def create_visibility(config: Configuration,
times: numpy.array,
frequency: numpy.array,
channel_bandwidth,
phasecentre: SkyCoord,
weight: float,
polarisation_frame=PolarisationFrame('stokesI'),
integration_time=1.0) -> Visibility:
""" Create a Visibility from Configuration, hour angles, and direction of source
Note that we keep track of the integration time for BDA purposes
:param config: Configuration of antennas
:param times: hour angles in radians
:param frequency: frequencies (Hz] [nchan]
:param weight: weight of a single sample
:param phasecentre: phasecentre of observation
:param channel_bandwidth: channel bandwidths: (Hz] [nchan]
:param integration_time: Integration time ('auto' or value in s)
:param polarisation_frame: PolarisationFrame('stokesI')
:return: Visibility
"""
assert phasecentre is not None, "Must specify phase centre"
if polarisation_frame is None:
polarisation_frame = correlate_polarisation(config.receptor_frame)
nch = len(frequency)
ants_xyz = config.data['xyz']
nants = len(config.data['names'])
nbaselines = int(nants * (nants - 1) / 2)
ntimes = len(times)
npol = polarisation_frame.npol
nrows = nbaselines * ntimes * nch
nrowsperintegration = nbaselines * nch
row = 0
rvis = numpy.zeros([nrows, npol], dtype='complex')
rweight = weight * numpy.ones([nrows, npol])
rtimes = numpy.zeros([nrows])
rfrequency = numpy.zeros([nrows])
rchannel_bandwidth = numpy.zeros([nrows])
rantenna1 = numpy.zeros([nrows], dtype='int')
rantenna2 = numpy.zeros([nrows], dtype='int')
ruvw = numpy.zeros([nrows, 3])
# Do each hour angle in turn
for iha, ha in enumerate(times):
# Calculate the positions of the antennas as seen for this hour angle
# and declination
ant_pos = xyz_to_uvw(ants_xyz, ha, phasecentre.dec.rad)
rtimes[row:row + nrowsperintegration] = ha * 43200.0 / numpy.pi
# Loop over all pairs of antennas. Note that a2>a1
for a1 in range(nants):
for a2 in range(a1 + 1, nants):
rantenna1[row:row + nch] = a1
rantenna2[row:row + nch] = a2
# Loop over all frequencies and polarisations
for ch in range(nch):
# noinspection PyUnresolvedReferences
k = frequency[ch] / constants.c.value
ruvw[row, :] = (ant_pos[a2, :] - ant_pos[a1, :]) * k
rfrequency[row] = frequency[ch]
rchannel_bandwidth[row] = channel_bandwidth[ch]
row += 1
assert row == nrows
rintegration_time = numpy.full_like(rtimes, integration_time)
vis = Visibility(uvw=ruvw,
time=rtimes,
antenna1=rantenna1,
antenna2=rantenna2,
frequency=rfrequency,
vis=rvis,
weight=rweight,
imaging_weight=rweight,
integration_time=rintegration_time,
channel_bandwidth=rchannel_bandwidth,
polarisation_frame=polarisation_frame)
vis.phasecentre = phasecentre
vis.configuration = config
log.info("create_visibility: %s" % (vis_summary(vis)))
assert isinstance(vis, Visibility), "vis is not a Visibility: %r" % vis
return vis