What's the difference between Antenna1 and Antenna2? Axis definitions in plotms: Difference between revisions
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== Amp == | == Amp == | ||
Data amplitudes in units | Data amplitudes in units which are proportional to Jansky (for data which are fully calibrated, the units should be Jy). | ||
== Phase == | == Phase == |
Revision as of 13:47, 19 February 2010
Plotms is a powerful tool for visualizing your measurement set, and provides you with lots of choices for X- and Y- Axes. It's not always clear what the choices mean, so below are some explanations.
Scan
The scan number, as listed by listobs.
Field
The field number, as listed by listobs. Typically, each source should have a different field number.
Time
The time at which the visibility was observed, given in terms of calendar year (yyyy/mm/dd/hh:mm:ss.ss)
Time_interval
The integration time in seconds.
Spw
The spectral window number (analogous to what VLA users know as an IF). The characteristics of each spectral window are listed in listobs.
Channel
The frequency channel number.
Frequency
Frequency in units of GHz. The frame for the frequency (e.g., topocentric, barycentric, LSRK) can be set in the Trans tab of plotms.
Corr
Correlations which have been assigned integer IDs:
- 5: RR
- 6: RL
- 7: LR
- 8: LL
Antenna1, Antenna2
Antenna1 is the first antenna in a baseline pair; for example, for baseline 2-4, Antenna1 = 2. Antenna2 is the second antenna in a baseline pair; so for baseline 2-4, Antenna2 = 4. Antennae are numbered according to the antenna IDs listed in listobs.
Antenna
For plotting antenna-based quantities like elevation, use just plain Antenna. Antennae are numbered according to the antenna IDs listed in listobs.
Baseline
The baseline number.
UVDist, UVDist_L
Projected baseline separations. UVDist is in units of meters, while UVDist_L is in units of the observing wavelength (lambda, not kilolambda). Note that UVDist_L is a function of frequency, while UVDist is not. Therefore, when plotting UVDist_L, there will be a different data point for each frequency channel.
U, V, W
u, v, and w in units of meters.
Beta Alert: Some day soon there will be U_L, V_L, and W_L, which will be in units of observing wavelength. Like UVDist_L, these quantities are functions of frequency and will change across your bandwidth.
Velocity
Velocity in units of km/s. Velocity is defined by parameters in the Trans tab of plotms, namely:
- the reference frame (barycentric, topocentric, etc.)
- the velocity definition (radio, optical, true, etc.)
- the rest frequency of the spectral line.
Amp
Data amplitudes in units which are proportional to Jansky (for data which are fully calibrated, the units should be Jy).
Phase
Data phases in units of degrees.
Real, Imag
The real and imaginary parts of the visibility in units of Jansky.
Flag
Data which are flagged have Flag = 1, whereas unflagged data are set to Flag = 0. Note that, to display flagged data, you will have to click on the Display tab and choose a 'Flagged Points Symbol'.
Azimuth, Ant-Azimuth
Antenna azimuth in units of degrees. Azimuth is the baseline-based version, while Ant-Azimuth is the antenna-based version.
Elevation, Ant-Elevation
Antenna elevation in units of degrees. Elevation is the baseline-based version, while Ant-Elevation is the antenna-based version.
HourAngle
Hour Angle in units of hours. This is a baseline-based quantity.
ParAngle, Ant-ParAng
Parallactic angle in units of degrees (???)
???
It appears that Ant-ParAng is in reasonable units to be in degrees, whereas ParAng gives totally different numbers, which are too small to be in degrees.
???
Row
Data row number.
???
For each time integration, is there a new row created?
???
FlagRow
???
I would think this is the row number in the flag table for flagged data, but it appears that all data, even that which is flagged, has FlagRow = 0
???
Last checked in CASA Version 3.0.1 (r10380).
--Laura Chomiuk 04:42, 19 February 2010 (UTC)