NRAO Home > CASA > CASA Toolkit Reference Manual
coordsys.toabs - Function

1.1.3 Convert relative coordinate to absolute


Description

This function converts a relative coordinate to an absolute coordinate. The coordinate may be a pixel coordinate or a world coordinate.

If the coordinate is a pixel coordinate, it is supplied as a numeric vector. If the coordinate is a world coordinate, you may give it in all of the formats described in the formatting discussion.

If the coordinate value is supplied by a Coordsys tool function (e.g. toworld) then the coordinate ’knows’ whether it is world or pixel (and absolute or relative). However, you might supply the value from some other source as a numeric vector (which could be world or pixel) in which case you must specify whether it is a world or pixel coordinate via the isworld argument.

Arguments





Inputs

value

Relative coordinate

allowed:

any

Default:

variant

isworld

Is coordinate world or pixel? Default is unset.

allowed:

int

Default:

-1

Returns
record

Example

 
 
"""  
#  
print "\t----\t toabs Ex 1 \t----"  
csys = cs.newcoordsys(direction=T, spectral=T)  
aw = csys.toworld([100,100,24], ’s’)  
rw = csys.torel(aw)  
aw2 = csys.toabs(rw)  
print aw  
#{’ar_type’: ’absolute’, ’pw_type’: ’world’,  
# ’string’: array([’23:53:19.77415678’, ’+01.40.00.84648186’,  
#                  ’1.41502400e+09 Hz’], dtype=’|S19’)}  
print rw  
#{’ar_type’: ’relative’, ’pw_type’: ’world’,  
# ’string’: array([’-6.00084720e+03 arcsec’, ’6.00084648e+03 arcsec’,  
#                  ’2.40000000e+04 Hz’], dtype=’|S23’)}  
print aw2  
#{’ar_type’: ’absolute’, ’pw_type’: ’world’,  
# ’string’: array([’23:53:19.77415672’, ’+01.40.00.84648000’,  
#                  ’1.41502400e+09 Hz’], dtype=’|S19’)}  
#  
"""  
 
 
This example uses world coordinates.  

Example

 
 
"""  
#  
print "\t----\t toabs Ex 2 \t----"  
csys = cs.newcoordsys(direction=T, spectral=T)  
ap = csys.topixel()           # Reference value  
rp = csys.torel(ap)  
ap2 = csys.toabs(rp)  
print ap  
#{’ar_type’: ’absolute’, ’pw_type’: ’pixel’, ’numeric’: array([ 0.,  0.,  0.])}  
print rp  
#{’ar_type’: ’relative’, ’pw_type’: ’world’,  
#     ’numeric’: array([  0.00000000e+00,   0.00000000e+00,  -1.41500000e+09])}  
print ap2  
#{’ar_type’: ’absolute’, ’pw_type’: ’world’, ’numeric’: array([ 0.,  0.,  0.])}  
#  
"""  
 
This example uses pixel coordinates.  

__________________________________________________________________


More information about CASA may be found at the CASA web page

Copyright 2016 Associated Universities Inc., Washington, D.C.

This code is available under the terms of the GNU General Public Lincense


Home | Contact Us | Directories | Site Map | Help | Privacy Policy | Search