OTRANS (Mar95)                   suntrans                   OTRANS (Mar95)



NAME
    OTRANS  --  spherical  harmonic  transform  of  folded  images  in a
    heliographic coordinate system to multi-image mode coefficient files
    
    
USAGE
    otrans inputl superfile trim_file (nsup_start ndat ngroup 
           tolerance)
    
    
PARAMETERS
    
    inputl
        input list of files
    
    superfile
        file name template for multi-image mode coefficient file  number
        for output mode coefficients
    
    trim_file
        ASCII    file    containing    the    specifications   for   the  
        latitude-longitude grid and the corresponding  mode  coefficient
        trimming  limits.   This  required  input  file  is generated by
        PLMTRIM  and  may  be  reused  for  all  images  with  the  same 
        latitude-longitude  grid  parameters,  maximum l value and all-m
        or even-m mode coefficients.
    
    (nsup_start = 1)
        starting multi-image mode coefficient  file  number  for  output
        mode coefficients
    
    (ndat = 6)
        maximum  number  of  data  sets  to  be  computed  in  parallel. 
        Efficiency peaks at about ndat=6.  Values between 1 and  20  are
        accepted.  Currently (1/1/94), ngroup*ndat<=20.
    
    (ngroup = 3)
        number  of  groups  of  images of size ndat to be written into a
        multi-image mode coefficient file.  Values between 1 and  3  are
        accepted.  Currently (1/1/94), ngroup*ndat<=20.
    
    (tolerance = 0.00001)
        tolerance  for  file  matching  in latitude.  Values larger than
        0.00000001 are accepted.
    
    
IMAGE HEADER WORDS
    
    LAT1
        most southerly latitude or sin(latitude) value
    
    LATTYPE
        type of spacing in latitude
    
    DATE-OBS
        date of observation, UT
    
    TIME-OBS
        time of observation, UT
    
    SITE
        observation site abreviation
    
    EPOCH
        Time of time sample 0 in UT, format yyyy/mm/dd.hh:mm:ss
    
    SER_SLOT
        time sample number of observation
    
    M_WEIGHT
        merge weight for image
    
    TOTNLONG
        total number of longitude points  across  the  disk--must  be  a
        power of 2
    
    BEGNLONG
        number  of  points  in  longitude  array  to  begin insertion of
        points from folded image in a heliographic coordinate system
    
    N_NORMAL
        number  of  data  points  in  folded  image  in  a  heliographic 
        coordinate system for normalizing spherical harmonic transform.
    
    
DESCRIPTION
    Task  OTRANS takes folded images in a heliographic coordinate system
    specified in the trimming limit  file  and  performs  the  spherical
    harmonic  transform.   A  user-determined  number  of  images may be
    processed  in  parallel.   The  mode  coefficients  for  each  image 
    processed   in  parallel  are  written  into  a  plane  of  a  three 
    dimensional multi-image mode coefficient file containing  the  group
    of images processed in parallel.
    
    
    
EXAMPLES
    
    1.   Perform  spherical harmonic transform on the folded images in a
    heliographic coordinate system found in inputl.lis  using  the  mode
    coefficient  trimming  limits  and  latitude-longitude  grid in file
    mod250.dat.  The first multi-image mode  coefficient  file  will  be
    named  july4mc0001.   The  multi-image  mode  coefficient files will
    each  contain  coefficients  from  6.   images,  with  the  possible 
    exception  of  the last multi-image mode coefficient file generated,
    which may contain fewer.
    
            su> otrans @inputl.lis mod250.dat july4mc
    
    2.  Perform spherical harmonic transform on the folded images  in  a
    heliographic  coordinate  system  found in inputl.lis using the mode
    coefficient trimming limits  and  latitude-longitude  grid  in  file
    mod250.dat.   The  super  image files will each contain coefficients
    from 6 images, with the possible exception of the  last  multi-image
    mode  coefficient  file  generated,  which  may  contain fewer.  The
    first multi-image mode coefficient file will be named s6te0010.
    
            su> otrans @inputl.lis mod250.dat s6te nsupim_start=10
    
    
    
TIME REQUIREMENTS
    If  more  than  three  images  are  transformed  in  parallel,   the 
    spherical  harmonic  transform  consumes  about one third of the cpu
    time required to process a set of data from  solar  disk  images  to
    time  series.   Time on a per image basis for the spherical harmonic
    transform with lmax=250 of images  of  dimensions  372x220  done  in
    groups  of  6  is  about  5  seconds  of  cpu time and 10 seconds of
    elapsed time on the DECstation 3100.   Time on  a  per  image  basis
    for  the  spherical  harmonic  transform  with lmax=750 of images of
    dimensions 880x1494 done in groups of 6 is about 150 seconds of  cpu
    time and 170 seconds of elapsed time on the DECstation 3100.
    
    
BUGS
    No  bugs  are  known to exist in task OTRANS.  OTRANS is designed to
    be used with either all m values or even m values.
    
    
SEE ALSO
    plmtrim, burst, sermake, im3dtrans
    
    helio_image
    
    modecoef_file