# Usage of angularSeparationOfDirections

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

### Usage:

```au.angularSeparationOfDirections(dir1, dir2, returnComponents=False)
```
By default, it returns the angle in radians. 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.angularSeparationOfDirections(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]: 1.2495785188322224

CASA <19>: au.angularSeparationOfDirections(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([ 1.24957852, -1.20056436, -0.51036395, -1.16168694])

```

-- ToddHunter - 2013-09-09

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