[daip] SPECR + UVFRE: Combining VLA datasets with different frequency axes.

[Nissim Kanekar]

Hi Eric,


> On 06/22/2017 03:40 PM, Nissim Kanekar wrote:
>>
>>  Hi Eric,
>>
>>  I've run into a problem with combining two VLA datasets with different
>>  frequency axes, using SPECR and UVFRE in 31DEC17. One dataset is from
>>  the VLA and has a bandwidth of 3.125 MHz and 128 channels (i.e. channel
>>  resolution of 24.41 kHz), while the other is from the JVLA and has a
>>  bandwidth of 4 MHz and 256 channels (i.e. channel resolution of 24.41
>>  kHz). The bands are also centred at different frequencies.
>>
>>  I first used SPECR with NPOINTS 160 to convert the JVLA dataset to a
>>  channel resolution of 25 kHz, and then SPECR with NPOINTS 125 to convert
>>  the VLA dataset to the same resolution. The VLA.SPECR dataset has a
>>  frequency of 1418.4974 MHz at channel 63 and 125 channels. I then SPLIT
>>  the JVLA.SPECR dataset to produce a dataset with 125 channels and 25 kHz
>>  resolution, and with a central frequency of 1418.8454 MHz (within half a
>>  channel of the value in the VLA dataset). And then ran UVFRE to regrid
>>  the JVLA.SPECR dataset to the VLA.SPECR dataset. The JVLA.UVFRE file now
>>  appears to have the same frequency structure as the VLA.SPECR dataset,
>>  i.e. 125 channels, with a frequency of 1418.4974 MHz at channel 63, and
>>  a channel resolution of 25 kHz. However, when I next run DBCON to
>>  combine the two files (keeping the VLA.SPECR file first and the
>>  JVLA.UVFRE file second), I get the following error message:
>> 
>> JEEVES> DBCON1:  Copied WX file from vol/cno/vers  1    8   1 to  1   11 
>> JEEVES> DBCON1:  1
>> JEEVES> DBCON1:  Copied OF file from vol/cno/vers  1    8   1 to  1   11 
>> JEEVES> DBCON1:  1
>> JEEVES> DBCON1:  Copied FO file from vol/cno/vers  1    8   1 to  1   11 
>> JEEVES> DBCON1:  1
>> JEEVES> DBCON1:  TABINI: KEY COUNTS     51     51 OR COLS     13     11
>>  DON'T MAT
>> JEEVES>          CH
>> JEEVES> DBCON1:  DBCAPP: ERROR    1 OPENING INPUT TABLE
>> JEEVES> DBCON1:  Appears to have ended successfully
>> JEEVES> DBCON1:  jeeves 31DEC17 TST: Cpu=     14.5  Real=     15  IO=
>>  12065
>> 
>>
>>  The DBCON output file now only contains the first datafile (the VLA
>>  dataset), when plotted with VPLOT.
>>
>>  If I try changing the order in DBCON, with the JVLA.UVFRE file first and
>>  the VLA.SPECR dataset second, I get a different error:
>> 
>> 
>> JEEVES> DBCON1:  Task DBCON  (release of 31DEC17) begins
>> JEEVES> DBCON1:  WARNING: COMBINING VISIBILITY DATA WITH DATAOF UNKNOWN 
>> JEEVES> DBCON1:  TYPE
>> JEEVES> DBCON1:  RA does not match, will shift second
>> JEEVES> DBCON1:  DEC does not match, will shift second
>> JEEVES> DBCON1:  Create ESO 461-36  .DBCON .   1 (UV)  on disk  1  cno   11
>> JEEVES> DBCON1:  Copied AN file from vol/cno/vers  1    7   1 to  1   11 
>> JEEVES> DBCON1:  1
>> JEEVES> DBCON1:  Copied AN file from vol/cno/vers  1    4   1 to  1   11 
>> JEEVES> DBCON1:  2
>> JEEVES> DBCON1:  DBMNGL: at output record     50000
>>  .....
>> JEEVES> DBCON1:  DBMNGL: at output record   2050000
>> JEEVES> DBCON1:  Copied WX file from vol/cno/vers  1    7   1 to  1   11 
>> JEEVES> DBCON1:  1
>> JEEVES> DBCON1:  DBCAPP: INPUT TABLES DO NOT MATCH
>> JEEVES> DBCON1:  Appears to have ended successfully
>>
>>  This time, the DBCON output appears to contain only the JVLA.UVFRE data
>>  (when plotted with VPLOT).
>>
>>  I'm not sure whether I'm making a mistake when combining the two files,
>>  or if there's some sort of a bug in UVFRE. Do you happen to know what's
>>  going on?
>> 
> Maybe you are making a mistake with VPLOT - do you have two subarrays? (Two 
> AN tables on the output).  VPLOT will only display 1 subarray at a time 
> usually number 1.  I don't have time to chase these errors right now but I am 
> not surprised if EVLA and old VLA tables do not match entirely.
>

You're absolutely right: I did have two AN tables in the output file. Didn't 
realize that VPLOT would only show a single sub-array; I thought it would show 
data from one sub-array and then data from the second sub-array. I just tried 
forcing DOARRAY 1 in DBCON and the DBCON output file now has a single AN table, 
and VPLOT shows both datasets. I guess the strange error message may not have 
been relevant?

Many thanks!

Hope all's well with you...

Best wishes,
Nissim