This TASK corrects observational positions of your data obtained with BEARS.
This operation is necessary, because observed positions with BEARS are distorted
from the regular grids due to the nature of beam transmission system (modified
Coude) of the 45 m radiotelescope.
The values of correction depend on the channels and elevation of the telescope:
The typical values for the most outer channels are 6-8 arcsec.
This TASK is recommended to be applied to data obtained with Nyquist (or one beam)
sampling.
This TASK should be applied to data without integration, because the correction value is different
for each scan: Usually spectra to be inputted to this TASK are made with a
TASK GCONV from raw data without integration.
Input file will be overwritten, if you do not open a new output file.
The present version of this TASK is "BPOS3".
Older versions of this task (BPOSC and BPOS2) had a bug:
BPOSC (versions earlier than 2002Jul9) returned wrong positions,
and both BPOSC and BPOS2 returned wrong positions if
the Position Angle of a map was not 0.
You should re-apply BPOS3 to data which have been
wrongly corrected using BPOS(C/2).
Calculated positions remain correct even if
the position correction is applied twice (or more).
* USAGE:
< Parameter window for Pos. Correct >
1. Setting up parameters
File Name (INPUT):
Specify a spectral file obtained with BEARS,
or select from [File List].
If you want to treat more than one file for input, mark a function
"Use temporary file to concatenate files" under the DONE button in the
[File List]. Then, you can select more than one file.
File Name (OUTPUT):
When you want to create a new output file,
specify a file name, and select a default extension
'BPOS3' or select a manual extension mode to type your desired
extension name.
Open New File
Select 'NO' or 'YES'.
2. Execution
Execute this TASK from the menu bar.
The TASK automatically ends.
The rough procedure of the correction is as follows.
Using observational positions
of each channel and CH33 (central channel) defined in the
observational table,
the corresponding coordiantes at the beam transmission system
are calculated. Then, the actual distortion is taken into account
with polynomial formulae. Subsequently, the actual observational
positions considering the distortion is calculated.
The (X,Y) coordinate (header values relative to map center
based on coordinate system used for mapping) is not corrected.
Using this coordinate
this TASK judges whether the correction is already done or not.