What's the difference between Antenna1 and Antenna2? Axis definitions in plotms

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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

???

Is this integration time?? In what units??

???

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.

???

What frequency is this exactly? It does not appear to change with the parameters in the Trans tab of plotms.

???

Corr

Correlations (e.g., RR, LL), which have been assigned integer IDs

???

By what scheme???

How can one find out what integer corresponds to which correlation???

Antenna1, Antenna2

For plotting baseline-based quantities like amplitude, either Antenna1 or Antenna2 must be chosen. 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; for example, 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, where baseline number is defined as ???

???

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).

???

Is this true about UVDist and meters?

???

U, V, W

u, v, and w in units of meters

???

Is this true about the units? Clearly it is in the same units as UVDist

???

Velocity

Velocity, which can be defined by parameters in the Trans tab of plotms, in units of km/s.

Amp

Data amplitudes in units of Jansky.

Phase

Data phases in units of degrees.

Real, Imag

The real and imaginary parts of the visibility in units of Jansky.

Flag

Azimuth

Elevation

HourAngle

ParAngle

Ant-Azimuth

Ant-Elevation

Ant-ParAng

Row

FlagRow


Last checked in CASA Version 3.0.1 (r10380).