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measures.position - Function

1.4.1 define a position measure


Description

position defines a position measure from the CLI. It has to specify a reference code, position quantity values (see introduction for the action on a scalar quantity with either a vector or scalar value),

and optionally it can specify an offset, which in itself has to be a position. Allowable reference codes are: WGS84 ITRF (World Geodetic System and International Terrestrial Reference Frame).
Note that additional ones may become available. Check in CASA with:

print "\t----\t position Ex 1 \t----"  
print me.listcodes(me.position())  
#{’normal’: [’ITRF’, ’WGS84’], ’extra’: []}

The position quantity values should be either longitude (angle), latitude(angle) and height(length); or x,y,z (length). See quantity for possible angle formats.

Arguments

Inputs

rf

reference code

allowed:

string

Default:

WGS84

v0

longitude or x

allowed:

any

Default:

variant

v1

latitude or y

allowed:

any

Default:

variant

v2

height or z

allowed:

any

Default:

variant

off

optional offset position measure

allowed:

record

Default:

Returns
record

Example

 
 
print "\t----\t position Ex 2 \t----"  
print me.position(’wgs84’,’30deg’,’40deg’,’10m’)  
#{’m0’: {’value’: 0.52359877559829882, ’unit’: ’rad’},  
# ’m1’: {’value’: 0.6981317007977319, ’unit’: ’rad’},  
# ’m2’: {’value’: 9.9999999999999982, ’unit’: ’m’},  
# ’refer’: ’WGS84’,  
# ’type’: ’position’}  
print me.observatory(’ATCA’)  
#{’m0’: {’value’: 2.6101423190348916, ’unit’: ’rad’},  
# ’m1’: {’value’: -0.5261379196128062, ’unit’: ’rad’},  
# ’m2’: {’value’: 6372960.2577234386, ’unit’: ’m’},  
# ’refer’: ’ITRF’,  
# ’type’: ’position’}  
 
###One can use a quantity-vectors  especially when dealing with multiple antenna positions  for e.g for 3 positions  
 
ants=me.position(’itrf’,qa.quantity([3828763.11,3828746.55, 3828727.43],’m’), qa.quantity([442449.106,442592.14, 442580.12],’m’),  
             qa.quantity([5064923.01, 5064923.01, 5064923.51],’m’))  
 
print ants  
 
#{’m0’: {’unit’: ’rad’,  
#        ’value’: array([ 0.11504897,  0.11508633,  0.1150838 ])},  
# ’m1’: {’unit’: ’rad’,  
#        ’value’: array([ 0.92031276,  0.92031276,  0.92031535])},  
# ’m2’: {’unit’: ’m’,  
#        ’value’: array([ 6364639.28758924,  6364639.27051283,  6364627.33064587])},  
# ’refer’: ’ITRF’,  
# ’type’: ’position’}  
 
 
 

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