The read-gsd-raster routine

 Because map making can be slow due to system overheads, it is quite often useful to create a basic data file first from the various map observation GSD files. The routine read-gsd-raster provides this capability. You should have a file open first, to which the data can be written, and the routine reminds you to turn off the screen chatter with >> s-l-f n if you don't want to see all the gory details.

Then, for example, the routine looks like this:

 >> r-g-r
 GSD scan number? [ 337] 333
 GSD version  5.3
 
 Use SET-LIST-FILE N to reduce output messages
 
 File number? (EOF to list) [1]  
 1  junk                                      W    -1
 File number? (EOF to list) [1] 
          (x,y) offset = ( -56.0, -56.0) arcsec
          rotation angles: x2y =  -90.0 deg.; v2y =    0.0 deg.
          (r,d) offset = ( -56.0, -56.0) arcsec
 
 
 Stack posn    Scan no    Title
     X          333      0333.0001   IRAS2227 JCMT 

 Perform DAS-MERGE before writing ? (Y/N) [Y] 
There are  222 overlapping channels
 Number of overlap channels to use? [ 111] 
 Adjust any DC offset quadrants? (Y/N) [N]

Then, away it goes. This routine does not fit baselines or truncate the noisy channels from the ends of the spectra, but it does das-merge the spectra as required. Subsequent application of the command merge-files allows data which should go in a single map cube to be combined. If one has two files containing grid, pattern, or raster data taken to a common centre merge-files will combine these data in a third file, averaging data taken at the same offsets. Thus this method is especially useful when one has data taken by several observers who have been confused about exactly where they should be observing, or when one has several observations of the same map grid. With the recent upgrade in speed resulting from improvements to the r-g-d routine this method does not confer any special advantage as to speed of application. It also tend to gobble up disk space due to the possibility of creating several large files rather than one.