Summarizing MeasurementSets
The MeasurementSet is the way CASA stores visibility data (the MS definition can be found in the Reference Material section). This page describes theree tasks to gain access to information stored in the MS: listobs displays observational details such as spatial (field), spectral (spectral window), temporal (scans), and polarization setup of an MS; listpartition provides information on how a MS was subdivided by the partition task (used for parallelized processing); listvis prints out the visibility values themselves.
Summarizing your MS (listobs)
An observational summary of the MS contents can be displayed with the listobs task. The inputs are:
vis = 'day2_TDEM0003_10s_norx' # Name of input visibility file (MS)
selectdata = True # Data selection parameters
field = '' # Field names or field index
# numbers: '' ==>all, field='0~2,3C286'
spw = '' # spectral-window/frequency/channel
antenna = '' # antenna/baselines: ''==>all, antenna ='3,VA04'
timerange = '' # time range: ''==>all,timerange='09:14:0~09:54:0'
correlation = '' # Select data based on correlation
scan = '' # scan numbers: ''==>all
intent = '' # Select data based on observation intent: ''==>all
feed = '' # multi-feed numbers: Not yet implemented
array = '' # (sub)array numbers: ''==>all
uvrange = '' # uv range: ''==>all; uvrange
# ='0~100klambda', default units=meters
observation = '' # Select data based on observation ID: ''==>all
verbose = True
listfile = '' # Name of disk file to write output: ''==>to terminal
listunfl = False # List unflagged row counts?
# If true, it can have significant negative performance
# impact
The summary (of the selected data) will be written to the logger, to the casapy-YYYYMMDD-HHMMSS.log file, and optionally to a file specified in the listfile parameter. For example,
listobs('n5921.ms')
results in a logger message like the following (also the format if a 'listfile' text file is requested):
listobs(vis="day2_TDEM0003_10s_norx",selectdata=True,spw="",field="",
antenna="",uvrange="",timerange="",correlation="",scan="",
intent="",feed="",array="",observation="",verbose=True,
listfile="",listunfl=False)
================================================================================
MeasurementSet Name: /Users/jott/casa/casatest/casa4.0/irc/day2_TDEM0003_10s_norx MS Version 2
================================================================================
Observer: Mark J. Mark Claussen Project: T.B.D.
Observation: EVLA
Data records: 290218 Total integration time = 10016 seconds
Observed from 26-Apr-2010/03:21:56.0 to 26-Apr-2010/06:08:52.0 (UTC)
ObservationID = 0 ArrayID = 0
Date Timerange (UTC) Scan FldId FieldName nRows SpwIds Average Interval(s) ScanIntent
26-Apr-2010/03:21:51.0 - 03:23:21.0 5 2 J0954+1743 2720 [0, 1] [10, 10]
03:23:39.0 - 03:28:25.0 6 3 IRC+10216 9918 [0, 1] [10, 10]
03:28:38.0 - 03:29:54.0 7 2 J0954+1743 2700 [0, 1] [10, 10]
03:30:08.0 - 03:34:53.5 8 3 IRC+10216 9918 [0, 1] [10, 10]
...
(nRows = Total number of rows per scan)
Fields: 4
ID Code Name RA Decl Epoch SrcId nRows
2 D J0954+1743 09:54:56.823626 +17.43.31.22243 J2000 2 65326
3 NONE IRC+10216 09:47:57.382000 +13.16.40.65999 J2000 3 208242
5 F J1229+0203 12:29:06.699729 +02.03.08.59820 J2000 5 10836
7 E J1331+3030 13:31:08.287984 +30.30.32.95886 J2000 7 5814
Spectral Windows: (2 unique spectral windows and 1 unique polarization setups)
SpwID Name #Chans Frame Ch1(MHz) ChanWid(kHz) TotBW(kHz) Corrs
0 Subband:0 64 TOPO 36387.229 125.000 8000.0 RR RL LR LL
1 Subband:0 64 TOPO 36304.542 125.000 8000.0 RR RL LR LL
Sources: 10
ID Name SpwId RestFreq(MHz) SysVel(km/s)
0 J1008+0730 0 0.03639232 -0.026
0 J1008+0730 1 0.03639232 -0.026
2 J0954+1743 0 0.03639232 -0.026
2 J0954+1743 1 0.03639232 -0.026
3 IRC+10216 0 0.03639232 -0.026
3 IRC+10216 1 0.03639232 -0.026
5 J1229+0203 0 0.03639232 -0.026
5 J1229+0203 1 0.03639232 -0.026
7 J1331+3030 0 0.03639232 -0.026
7 J1331+3030 1 0.03639232 -0.026
Antennas: 19:
ID Name Station Diam. Long. Lat. Offset from array center (m) ITRF Geocentric coordinates (m)
East North Elevation x y z
0 ea01 W09 25.0 m -107.37.25.2 +33.53.51.0 -521.9407 -332.7782 -1.1977 -1601710.017000 -5042006.928200 3554602.355600
1 ea02 E02 25.0 m -107.37.04.4 +33.54.01.1 9.8247 -20.4292 -2.7808 -1601150.059500 -5042000.619800 3554860.729400
2 ea03 E09 25.0 m -107.36.45.1 +33.53.53.6 506.0591 -251.8666 -3.5832 -1600715.948000 -5042273.187000 3554668.184500
3 ea04 W01 25.0 m -107.37.05.9 +33.54.00.5 -27.3562 -41.3030 -2.7418 -1601189.030140 -5042000.493300 3554843.425700
4 ea05 W08 25.0 m -107.37.21.6 +33.53.53.0 -432.1158 -272.1493 -1.5032 -1601614.091000 -5042001.655700 3554652.509300
5 ea07 N06 25.0 m -107.37.06.9 +33.54.10.3 -54.0667 263.8720 -4.2292 -1601162.593200 -5041829.000000 3555095.890500
6 ea08 N01 25.0 m -107.37.06.0 +33.54.01.8 -30.8810 -1.4664 -2.8597 -1601185.634945 -5041978.156586 3554876.424700
7 ea09 E06 25.0 m -107.36.55.6 +33.53.57.7 236.9058 -126.3369 -2.4443 -1600951.588000 -5042125.911000 3554773.012300
8 ea12 E08 25.0 m -107.36.48.9 +33.53.55.1 407.8394 -206.0057 -3.2252 -1600801.916000 -5042219.371000 3554706.449900
9 ea15 W06 25.0 m -107.37.15.6 +33.53.56.4 -275.8288 -166.7451 -2.0590 -1601447.198000 -5041992.502500 3554739.687600
10 ea19 W04 25.0 m -107.37.10.8 +33.53.59.1 -152.8599 -83.8054 -2.4614 -1601315.893000 -5041985.320170 3554808.304600
11 ea20 N05 25.0 m -107.37.06.7 +33.54.08.0 -47.8454 192.6015 -3.8723 -1601168.786100 -5041869.054000 3555036.936000
12 ea21 E01 25.0 m -107.37.05.7 +33.53.59.2 -23.8638 -81.1510 -2.5851 -1601192.467800 -5042022.856800 3554810.438800
13 ea22 N04 25.0 m -107.37.06.5 +33.54.06.1 -42.5986 132.8623 -3.5431 -1601173.953700 -5041902.660400 3554987.536500
14 ea23 E07 25.0 m -107.36.52.4 +33.53.56.5 318.0523 -164.1848 -2.6960 -1600880.570000 -5042170.388000 3554741.457400
15 ea24 W05 25.0 m -107.37.13.0 +33.53.57.8 -210.0944 -122.3885 -2.2581 -1601377.008000 -5041988.665500 3554776.393400
16 ea25 N02 25.0 m -107.37.06.2 +33.54.03.5 -35.6245 53.1806 -3.1345 -1601180.861480 -5041947.453400 3554921.628700
17 ea27 E03 25.0 m -107.37.02.8 +33.54.00.5 50.6647 -39.4832 -2.7249 -1601114.365500 -5042023.153700 3554844.945600
18 ea28 N08 25.0 m -107.37.07.5 +33.54.15.8 -68.9057 433.1889 -5.0602 -1601147.940400 -5041733.837000 3555235.956000
listobs shows information on the project itself like project code, observer and telescope, followed by the sequence of scans with start/stop times, integration times, and scan intents, a list of all fields with name and coordinates, available spectral windows and their shapes, a list of sources (field/spw combination), and finally the location of all antennas that are used in the observation. A row is an MS entry for a given time stamp and baseline (rows can be accessed e.g. via browsetable).
verbose=False would not show the complete list, in particular no information on the scans.
MMS summary (listpartition)
listobs can also be used for Multi MeasurementSets (MMSs). In addition, the task listpartition will provide additional information how the data is structured in preparation for parallelized processing (e.g. using the partition task). The inputs are:
# listpartition :: List the summary of a Multi-MS data set in the logger or in a file
vis = '' # Name of Multi-MS or normal MS.
createdict = False # Create and return a dictionary with
# Sub-MS information
listfile = '' # Name of ASCII file to save output:
# ''==>to terminal
For example,
listpartition('n5921.mms')
results in the logger messages:
This is a multi-MS with separation axis = scan,spw
Sub-MS Scan Spw Nchan Nrows Size
ngc5921.mms.0000.ms 2 [0] [63] 1890 27M
4 [0] [63] 756
5 [0] [63] 1134
6 [0] [63] 6804
ngc5921.mms.0001.ms 1 [0] [63] 4509 28M
3 [0] [63] 6048
7 [0] [63] 1512
The output can also be redirected to a python dictionary through the createdict parameter.
Listing MS data (listvis)
The listvis prints a list of the visibility data in an MS to the terminal or a textfile. The inputs are:
# listvis :: List MeasurementSet visibilities.
vis = '' # Name of input visibility file
options = 'ap' # List options: ap only
datacolumn = 'data' # Column to list: data, float_data, corrected, model,
# residual
field = '' # Field names or index to be listed: ''==>all
spw = '*' # Spectral window:channels: '\*'==>all, spw='1:5~57'
selectdata = False # Other data selection parameters
observation = '' # Select by observation ID(s)
average = '' # Averaging mode: ==>none (Not yet implemented)
showflags = False # Show flagged data (Not yet implemented)
pagerows = 50 # Rows per page
listfile = '' # Output file
For example,
Units of columns are: Date/Time(YYMMDD/HH:MM:SS UT), UVDist(wavelength), Phase(deg), UVW(m)
WEIGHT: 7
FIELD: 2
SPW: 0
Date/Time: RR: RL: LR: LL:
2010/04/26/ Intrf UVDist Chn Amp Phs Wt F Amp Phs Wt F Amp Phs Wt F Amp Phs Wt F U V W
------------|---------|------|----|--------------------|-------------------|-------------------|-------------------|---------|---------|---------|
03:21:56.0 ea01-ea02 72363 0: 0.005 -124.5 7 0.005 25.7 7 0.001 104.6 7 0.000 23.4 7 -501.93 -321.75 157.78
03:21:56.0 ea01-ea02 72363 1: 0.001 -4.7 7 0.001 -135.1 7 0.004 -14.6 7 0.001 19.9 7 -501.93 -321.75 157.78
03:21:56.0 ea01-ea02 72363 2: 0.002 17.8 7 0.002 34.3 7 0.005 -114.3 7 0.005 -149.7 7 -501.93 -321.75 157.78
03:21:56.0 ea01-ea02 72363 3: 0.004 -19.4 7 0.003 -79.2 7 0.002 -89.0 7 0.004 31.3 7 -501.93 -321.75 157.78
03:21:56.0 ea01-ea02 72363 4: 0.001 -16.8 7 0.004 -141.5 7 0.005 114.9 7 0.006 105.2 7 -501.93 -321.75 157.78
03:21:56.0 ea01-ea02 72363 5: 0.001 -29.8 7 0.009 -96.4 7 0.002 -125.0 7 0.002 -64.5 7 -501.93 -321.75 157.78
...
Type Q to quit, A to toggle long/short list, or RETURN to continue [continue]:
columns are:
COLUMN NAME DESCRIPTION ----------- ----------- Date/Time Time stamp of data sample (YYMMDD/HH:MM:SS UT) Intrf Interferometer baseline (antenna names) UVDist uv-distance (units of wavelength) Fld Field ID (if more than 1) SpW Spectral Window ID (if more than 1) Chn Channel number (if more than 1) (Correlated Correlated polarizations (eg: RR, LL, XY) polarization) Sub-columns are: Amp, Phs, Wt, F Amp Visibility amplitude Phs Visibility phase (deg) Wt Weight of visibility measurement F Flag: 'F' = flagged datum; ' ' = unflagged UVW UVW coordinates (meters)
Note that MS listings can be very large. Use selectdata=True and subselect the data to obtain the desired information as much as possible.