Usage of angularSeparationOfDirectionsArcsec

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 Accepts two direction dictionaries and returns the separation in arc seconds. It computes great circle angle using the Vincenty formula. See also angularSeparationOfDirections, angularSeparationOfScans, angularSeparationOfStrings, angularSeparationOfPlanets, angularSeparation, angularSeparationRadians, and angularSeparationRadiansTuples.

Usage:

au.angularSeparationOfDirectionsArcsec(dir1, dir2, returnComponents=False)
By default, it returns only the separation angle. If returnComponents == True, then it returns: [angle, ra_angle, dec_angle, ra_angle*cos(Dec)]

Examples:

CASA <15>: ms.open('uid___A002_X1465d3_Xc7.ms')
  Out[15]: True
CASA <16>: a=ms.getfielddirmeas(fieldid=0)
CASA <17>: b=ms.getfielddirmeas(fieldid=1)
CASA <18>: au.angularSeparationOfDirectionsArcsec(a,b)
{'type': 'direction', 'm1': {'value': -0.51036394872856283, 'unit': 'rad'}, 'm0': {'value': -1.20056435950273, 'unit': 'rad'}, 'refer': 'J2000'} {'type': 'direction', 'm1': {'value': 0.0, 'unit': 'rad'}, 'm0': {'value': 0.0, 'unit': 'rad'}, 'refer': 'J2000'}
  Out[18]:  257744.07107746199

CASA <19>: au.angularSeparationOfDirectionsArcsec(a,b,True)
{'type': 'direction', 'm1': {'value': -0.51036394872856283, 'unit': 'rad'}, 'm0': {'value': -1.20056435950273, 'unit': 'rad'}, 'refer': 'J2000'} {'type': 'direction', 'm1': {'value': 0.0, 'unit': 'rad'}, 'm0': {'value': 0.0, 'unit': 'rad'}, 'refer': 'J2000'}
  Out[19]: array([ 257744.07107746, -247634.175, -105270.121, -239615.13098521])

-- ToddHunter - 2013-09-09

This topic: ALMA > TWikiUsers > ToddHunter > CasaExtensions > AngularSeparationOfDirectionsArcsec
Topic revision: 2013-09-09, ToddHunter
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