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coordsys.projection - Function

1.1.3 Recover the direction coordinate projection


Description

If the Coordinate System contains a direction coordinate, this function can be used to recover information about the projection. For discussion about celestial coordinate systems, including projections, see the papers by Mark Calabretta and Eric Greisen. The initial draft from 1996 (implemented in CASA. Background information can be found here.

What this function returns depends upon the value you assign to type.

You can change the projection with setprojection.

If the Coordinate System does not contain a direction coordinate, an exception is generated.

Arguments





Inputs

type

Type of projection. Defaults to current projection.

allowed:

string

Default:

Returns
record

Example

 
 
"""  
#  
print "\t----\t projection Ex 1 \t----"  
csys = cs.newcoordsys(direction=T)  
print csys.projection()  
#{’type’: ’SIN’, ’parameters’: [0.0, 0.0]}  
print csys.projection(’all’)  
#{’all’: True, ’types’: [’AZP’, ’TAN’, ’SIN’, ’STG’, ’ARC’, ’ZPN’, ’ZEA’,  
# ’AIR’, ’CYP’, ’CAR’, ’MER’, ’CEA’, ’COP’, ’COD’, ’COE’, ’COO’, ’BON’,  
# ’PCO’, ’SFL’, ’PAR’, ’AIT’, ’MOL’, ’CSC’, ’QSC’, ’TSC’]}  
print csys.projection(’ZPN’)  
#{’nparameters’: 100}  
#  
"""  
 
We first recover the projection type and parameters from  
the direction coordinate.  Then we find the list of all  
possible projection types.  FInally, we recover the number of  
parameters required to describe the ’ZPN’ projection.  

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