def parse_subbands(subtables):
origin_table = subtables['LOFAR_ORIGIN']
num_chans = unique_column_values(origin_table, "NUM_CHAN")
if len(num_chans) == 1:
return num_chans[0]
else:
raise Exception("Cannot handle varying numbers of channels in image")
def parse_antennaset(subtables):
observation_table = subtables['LOFAR_OBSERVATION']
antennasets = unique_column_values(observation_table, "ANTENNA_SET")
if len(antennasets) == 1:
return antennasets[0]
else:
raise Exception("Cannot handle multiple antenna sets in image")
def parse_subbandwidth(subtables):
# subband
# see http://www.lofar.org/operations/doku.php?id=operator:background_to_observations&s[]=subband&s[]=width&s[]=clock&s[]=frequency
freq_units = {
'Hz': 1,
'kHz': 10 ** 3,
'MHz': 10 ** 6,
'GHz': 10 ** 9,
}
observation_table = subtables['LOFAR_OBSERVATION']
clockcol = observation_table.col('CLOCK_FREQUENCY')
clock_values = unique_column_values(observation_table, "CLOCK_FREQUENCY")
if len(clock_values) == 1:
clock = clock_values[0]
unit = clockcol.getkeyword('QuantumUnits')[0]
trueclock = freq_units[unit] * clock
subbandwidth = trueclock / 1024
return subbandwidth
else:
raise Exception("Cannot handle varying clocks in image")
