1.3.1.0 measures.measure

measures.measure - Function

1.3.1 convert a measure to another reference
Description

measure converts measures (epoch, direction etc.) from one reference to another. It will, for instance, convert a direction from J2000 to AZEL representation.
Its arguments are a measure, an output reference code (see the individual measures for the allowable codes (direction, position, epoch, frequency, doppler, radialvelocity, baseline, uvw, earthmagnetic)), and an optional offset of the same type as the main measure. The offset will be subtracted from the result before it is returned.
In some cases (see the individual measures for when), more information than just a reference code is necessary. E.g. the above example of a conversion to AZEL, needs to know for when, and where on Earth we want it. This information is stored in a reference frame. Measures are set in the reference frame with the doframe function. The frame is tool wide.
Arguments


Inputs
v	measure to be converted
	allowed:	any
	Default:	record
rf	output reference code
	allowed:	string
	Default:
off	optional output offset measure
	allowed:	any
	Default:	record

Returns
anyrecord

Example

"""
#
print "\t----\t measure Ex 1 \t----"
a = me.epoch(’utc’,’today’)         # a time
print a
#{’m0’: {’value’: 54054.872957673608, ’unit’: ’d’},
# ’refer’: ’UTC’,
# ’type’: ’epoch’}
print me.doframe(me.source(’1934-638’))
print me.measure(a, ’tai’) # convert to IAT
#{’m0’: {’value’: 54054.873339618054, ’unit’: ’d’},
# ’refer’: ’TAI’,
# ’type’: ’epoch’}
print me.doframe(a) # set time in frame
#True
print me.doframe(me.observatory(’ALMA’)) # set position in frame
#True
b=me.direction(’j2000’, qa.toangle(’0h’), ’-30deg’)  # a direction
print b
#{’m0’: {’value’: 0.0, ’unit’: ’rad’},
# ’m1’: {’value’: -0.52359877559829882, ’unit’: ’rad’},
# ’refer’: ’J2000’,
# ’type’: ’direction’}
print me.measure(b, ’azel’) # convert to AZEL
#{’m0’: {’value’: 1.9244096810822324, ’unit’: ’rad’},
# ’m1’: {’value’: 0.76465385681363052, ’unit’: ’rad’},
# ’refer’: ’AZEL’,
# ’type’: ’direction’}
print qa.angle(me.getvalue(me.measure(b,’azel’))[’m0’])     # show as angles
#[’+110.15.38’]
print qa.angle(me.getvalue(me.measure(b,’azel’))[’m1’])
#[’+043.48.41’]
#
"""

Another example:

"""
#
print "\t----\t measure Ex 2 \t----"
# Fill the frame with necessary information
print me.doframe(me.epoch(’utc’,’today’))
#True
print me.doframe(me.observatory(’ALMA’))
#True
print me.doframe(me.direction(’mars’))
#True
a=qa.unit(’1GHz’)
print a
#{’value’: 1.0, ’unit’: ’GHz’}
m=me.frequency(’lsrk’,qa.quantity(qa.getvalue(a),qa.getunit(a)))
print m
#{’m0’: {’value’: 1000000000.0, ’unit’: ’Hz’},
# ’refer’: ’LSRK’,
# ’type’: ’frequency’}
print me.measure(m,’lsrd’)
#{’m0’: {’value’: 1000001766.3928765, ’unit’: ’Hz’},
# ’refer’: ’LSRD’,
# ’type’: ’frequency’}
#
"""

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