def phaserotate_visibility(vis: Visibility, newphasecentre: SkyCoord, tangent=True, inverse=False) -> Visibility:
"""
Phase rotate from the current phase centre to a new phase centre
If tangent is False the uvw are recomputed and the visibility phasecentre is updated.
Otherwise only the visibility phases are adjusted
:param vis: Visibility to be rotated
:param newphasecentre:
:param tangent: Stay on the same tangent plane? (True)
:param inverse: Actually do the opposite
:return: Visibility
"""
assert isinstance(vis, Visibility), "vis is not a Visibility: %r" % vis
l, m, n = skycoord_to_lmn(newphasecentre, vis.phasecentre)
# No significant change?
if numpy.abs(n) > 1e-15:
# Make a new copy
newvis = copy_visibility(vis)
phasor = simulate_point(newvis.uvw, l, m)
nvis, npol = vis.vis.shape
# TODO: Speed up (broadcast rules not obvious to me)
if inverse:
for i in range(nvis):
for pol in range(npol):
newvis.data['vis'][i, pol] *= phasor[i]
else:
for i in range(nvis):
for pol in range(npol):
newvis.data['vis'][i, pol] *= numpy.conj(phasor[i])
# To rotate UVW, rotate into the global XYZ coordinate system and back. We have the option of
# staying on the tangent plane or not. If we stay on the tangent then the raster will
# join smoothly at the edges. If we change the tangent then we will have to reproject to get
# the results on the same image, in which case overlaps or gaps are difficult to deal with.
if not tangent:
if inverse:
xyz = uvw_to_xyz(vis.data['uvw'], ha=-newvis.phasecentre.ra.rad, dec=newvis.phasecentre.dec.rad)
newvis.data['uvw'][...] = \
xyz_to_uvw(xyz, ha=-newphasecentre.ra.rad, dec=newphasecentre.dec.rad)[...]
else:
# This is the original (non-inverse) code
xyz = uvw_to_xyz(newvis.data['uvw'], ha=-newvis.phasecentre.ra.rad, dec=newvis.phasecentre.dec.rad)
newvis.data['uvw'][...] = xyz_to_uvw(xyz, ha=-newphasecentre.ra.rad, dec=newphasecentre.dec.rad)[
...]
newvis.phasecentre = newphasecentre
return newvis
else:
return vis
def test_phase_rotate(self):
uvw = numpy.array([(1, 0, 0), (0, 1, 0), (0, 0, 1)])
pos = [
SkyCoord(17, 35, unit=u.deg),
SkyCoord(17, 30, unit=u.deg),
SkyCoord(12, 30, unit=u.deg),
SkyCoord(11, 35, unit=u.deg),
SkyCoord(51, 35, unit=u.deg),
SkyCoord(15, 70, unit=u.deg)
]
# Sky coordinates to reproject to
for phasecentre in pos:
for newphasecentre in pos:
# Rotate UVW
xyz = uvw_to_xyz(uvw, -phasecentre.ra.rad, phasecentre.dec.rad)
uvw_rotated = xyz_to_uvw(xyz, -newphasecentre.ra.rad,
newphasecentre.dec.rad)
# Determine phasor
l_p, m_p, n_p = skycoord_to_lmn(phasecentre, newphasecentre)
phasor = simulate_point(uvw_rotated, l_p, m_p)
for sourcepos in pos:
# Simulate visibility at old and new phase centre
l, m, _ = skycoord_to_lmn(sourcepos, phasecentre)
vis = simulate_point(uvw, l, m)
l_r, m_r, _ = skycoord_to_lmn(sourcepos, newphasecentre)
vis_rotated = simulate_point(uvw_rotated, l_r, m_r)
# Difference should be given by phasor
assert_allclose(vis * phasor, vis_rotated, atol=1e-10)
def transform(x, y, z, ha, dec):
"""
:param x:
:param y:
:param z:
:param ha:
:param dec:
:return:
"""
res = xyz_to_uvw(numpy.array([x, y, z]), numpy.radians(ha), numpy.radians(dec))
assert_allclose(numpy.linalg.norm(res), numpy.linalg.norm([x, y, z]))
assert_allclose(uvw_to_xyz(res, numpy.radians(ha), numpy.radians(dec)), [x, y, z])
return res