coordsys.summary - Function

Summarize basic information about the Coordinate System

Synopsis
summary(doppler, list)

Arguments

doppler	in	List velocity information with this doppler definition
		Allowed:	String
		Default:	RADIO
list	in	List to global logger
		Allowed:	Boolean
		Default:	T

Returns
T, fail, or Vector of strings

Description

This function (short-hand name s) summarizes the information contained in the Coordinate System. For spectral coordinates, the information is listed as a velocity as well as a frequency. The argument doppler allows you to specify what doppler convention it is listed in. You can choose from radio, optical and beta. Alternative names are z for optical, and relativistic for beta. The default is radio. The definitions are

radio: 1 - F
optical: -1 + 1/F
beta: (1 - F²)/(1 + F²)

where F = $\nu$ / $\nu_{0}^{}$ and $\nu_{0}^{}$ is the rest frequency. If the rest frequency has not been set in your image, you can set it with the function setrestfrequency.

These velocity definitions are provided by the measures system via the Doppler measure (see example).

If you set list=F, then the summary will not be written to the global logger. However, the return value will be a vector of strings holding the summary information, one string per line of the summary.

For direction and spectral coordinates, the reference frame (e.g. J2000 or LSRK) is also listed. Along side this, in parentheses, will be the conversion reference frame as well (if it is different from the native reference frame). See function setconversion to see what this means.

Example

- d := dm.doppler('beta')
- dm.listcodes(d)
[normal=RADIO Z RATIO BETA GAMMA OPTICAL TRUE RELATIVISTIC, extra=] 
-
- cs := coordsys(direction=T, spectral=T)
- cs.summary()
-
Direction reference : J2000
Spectral  reference : LSRK (-> BARY)
Velocity  type      : RADIO
Rest frequency      : 1.42041e+09 Hz

Telescope        : ATCA
Observer         : Karl Jansky
Date observation : 2000/07/04/10:01:11

Axis Type      Name             Proj   Coord value at pixel    Coord incr Units
------------------------------------------------------------------------------- 
1    Direction Right Ascension   SIN  00:00:00.000     1.00 -6.000000e+01 arcsec
2    Direction Declination       SIN +00.00.00.000     1.00  6.000000e+01 arcsec
3    Spectral  Frequency              1.415000e+09     1.00  1.000000e+03 Hz
               Velocity               1.140944e+03     1.00 -2.110611e-01 km/s

Next: coordsys.telescope - Function Up: coordsys - Tool Previous: coordsys.stokes - Function Contents Index

	Package	general
	Module	images
	Tool	coordsys