def readMS(fn, sbs, column='DATA'):
"""Return the visibilites and UVW coordinates from a SE607 LOFAR XST format file
fn: XST filename
column: string, data column
sbs: 1-D array of subband IDs
returns:
vis: visibilities [4, Nsamples, Nsubbands]
uvw: UVW coordinates [Nsamples, 3, Nsubbands]
freqs: frequencies [Nsubbands]
obsdata: [latitude, longitude, LST]
"""
try:
import casacore.tables as tbls
except ImportError:
print 'ERROR: could not import casacore.tables, cannot read measurement sets'
exit(1)
MS = tbls.table(fn, readonly=True)
data_column = column.upper()
uvw = MS.col('UVW').getcol() # [vis id, (u,v,w)]
vis = MS.col(data_column).getcol() #[vis id, freq id, stokes id]
vis = vis[:,sbs,:] #select subbands
MS.close()
# lat/long/lst information
ANTS = tbls.table(fn + '/ANTENNA')
positions = ANTS.col('POSITION').getcol()
ant0Lat, ant0Long, ant0hgt = ecef.ecef2geodetic(positions[0,0], positions[0,1], positions[0,2], degrees=False) # use the first antenna in the table to get the array lat/long
ANTS.close()
SRC = tbls.table(fn + '/SOURCE')
direction = SRC.col('DIRECTION').getcol()
obsLat = direction[0,1]
obsLong = ant0Long
LSTangle = direction[0,0]
SRC.close()
# freq information, convert uvw coordinates
SW = tbls.table(fn + '/SPECTRAL_WINDOW')
freqs = SW.col('CHAN_FREQ').getcol()[0, sbs] # [nchan]
print 'SUBBANDS:', sbs, '(', freqs/1e6, 'MHz)'
SW.close()
# TODO: check rotation reference is the same as with LOFAR data, north pole is dec=+90, ra=0
# in order to accommodate multiple observations at different times/sidereal times all the positions need to be rotated relative to sidereal time 0
print 'LST:', LSTangle
rotAngle = float(LSTangle) - obsLong # adjust LST to that of the Observatory longitutude to make the LST that at Greenwich
# to be honest, the next two lines change the LST to make the images come out but i haven't worked out the coordinate transforms, so for now these work without justification
rotAngle += np.pi
rotAngle *= -1
# Rotation matrix for antenna positions
rotMatrix = np.array([[np.cos(rotAngle), -1.*np.sin(rotAngle), 0.],
[np.sin(rotAngle), np.cos(rotAngle), 0.],
[0., 0., 1.]]) #rotate about the z-axis
uvwRot = np.dot(uvw, rotMatrix).reshape(uvw.shape[0], uvw.shape[1], 1)
uvwRotRepeat = np.repeat(uvwRot, len(sbs), axis=2)
return np.transpose(vis, (2,0,1)), uvwRotRepeat, freqs, [obsLat, obsLong, LSTangle]
def readMS(fn, sbs, column='DATA'):
"""Return the visibilites and UVW coordinates from a Measurement Set
fn: MS filename
column: string, data column
sbs: 1-D array of subband IDs
returns:
vis: visibilities [4, Nsamples, Nsubbands]
uvw: UVW coordinates [Nsamples, 3, Nsubbands]
freqs: frequencies [Nsubbands]
obsdata: [latitude, longitude, LST]
"""
try:
import casacore.tables as tbls
except ImportError:
print 'ERROR: could not import casacore.tables, cannot read measurement sets'
exit(1)
MS = tbls.table(fn, readonly=True)
data_column = column.upper()
uvw = MS.col('UVW').getcol() # [vis id, (u,v,w)]
vis = MS.col(data_column).getcol() #[vis id, freq id, stokes id]
vis = vis[:,sbs,:] #select subbands
MS.close()
# lat/long/lst information
ANTS = tbls.table(fn + '/ANTENNA')
positions = ANTS.col('POSITION').getcol()
ant0Lat, ant0Long, ant0hgt = ecef.ecef2geodetic(positions[0,0], positions[0,1], positions[0,2], degrees=False) # use the first antenna in the table to get the array lat/long
ANTS.close()
SRC = tbls.table(fn + '/SOURCE')
direction = SRC.col('DIRECTION').getcol()
obsLat = direction[0,1]
obsLong = ant0Long
LSTangle = direction[0,0]
SRC.close()
# freq information, convert uvw coordinates
SW = tbls.table(fn + '/SPECTRAL_WINDOW')
freqs = SW.col('CHAN_FREQ').getcol()[0, sbs] # [nchan]
print 'SUBBANDS:', sbs, '(', freqs/1e6, 'MHz)'
SW.close()
# TODO: check rotation reference is the same as with LOFAR data, north pole is dec=+90, ra=0
# in order to accommodate multiple observations at different times/sidereal times all the positions need to be rotated relative to sidereal time 0
print 'LST:', LSTangle
rotAngle = float(LSTangle) - obsLong # adjust LST to that of the Observatory longitutude to make the LST that at Greenwich
# to be honest, the next two lines change the LST to make the images come out but i haven't worked out the coordinate transforms, so for now these work without justification
rotAngle += np.pi
rotAngle *= -1
# Rotation matrix for antenna positions
rotMatrix = np.array([[np.cos(rotAngle), -1.*np.sin(rotAngle), 0.],
[np.sin(rotAngle), np.cos(rotAngle), 0.],
[0., 0., 1.]]) #rotate about the z-axis
uvwRot = np.dot(uvw, rotMatrix).reshape(uvw.shape[0], uvw.shape[1], 1)
uvwRotRepeat = np.repeat(uvwRot, len(sbs), axis=2)
return np.transpose(vis, (2,0,1)), uvwRotRepeat, freqs, [obsLat, obsLong, LSTangle]
def lofarArrayLatLong(lofarStation, arrayType='LBA'):
"""Return the Latitude, Longitude, Elevation of a LOFAR station
lofarStation: instance, see lofarConfig.py
arrayType: string, LOFAR array type
returns: latitude (degs), longitude (degs), elevation (m)
"""
#lon, lat, elev = lofarStation.antArrays.location[lofarConfig.rcuInfo[fDict['rcu']]['array_type']]
arr_xyz = lofarStation.antField.location[arrayType]
lat, lon, elev = ecef.ecef2geodetic(arr_xyz[0], arr_xyz[1], arr_xyz[2], degrees=True)
print 'LON(deg):', lon, 'LAT(deg):', lat, 'ELEV(m):', elev
return lat, lon, elev
def lofarArrayLatLong(lofarStation, arrayType='LBA'):
"""Return the Latitude, Longitude, Elevation of a LOFAR station
lofarStation: instance, see lofarConfig.py
arrayType: string, LOFAR array type
returns: latitude (degs), longitude (degs), elevation (m)
"""
#lon, lat, elev = lofarStation.antArrays.location[lofarConfig.rcuInfo[fDict['rcu']]['array_type']]
arr_xyz = lofarStation.antField.location[arrayType]
lat, lon, elev = ecef.ecef2geodetic(arr_xyz[0], arr_xyz[1], arr_xyz[2], degrees=True)
print 'LON(deg):', lon, 'LAT(deg):', lat, 'ELEV(m):', elev
return lat, lon, elev
