Help for PARSE

PURPOSE:
PARSE separates images into their periodic components. That is, each output
is created from every nth line (HORIZONTAL mode) or every nth sample
(VERTICAL mode) from the input image, with each particular output starting
from a different line (or sample).  Its original intent was to separate one 
image into images of each component detector (sensor), but it may be used 
whenever an image of every nth line or nth sample is desired.

The user may choose to output only selected bands (for multichannel data) or
selected sensors (lines or samples). Each output image will contain the
selected sensors for one band in the BY_BAND mode, or the selected bands for
one sensor in the BY_SENSOR mode.

There is also a REVERSE mode, which performs the reverse operation.  That 
is, given multiple inputs from an image that has been PARSE'd apart, an
output image will be rebuilt.
Examples:

  PARSE ASTER_TIR (CH10,CH11,C12,C13,C14) COUNT=10

In this case, an input with 5 channels in the input file is split into 5
output images, one per channel.  Each output file will contain 10 bands,
each band is taken from every tenth input line, Band 1 starting with Line 1,
Band 2 starting with Line 2, etc.


  PARSE ASTER_SWIR (ODD,EVEN) 'VERTICAL 'BY_SENSOR COUNT=2

In this example, an input is split in two, with the first output containing
the odd numbered samples, and the second output holding the even numbered
samples.
  PARSE ASTER_TIR (S1,S7,S10) 'BY_SENSOR COUNT=10 SENSORS=(1,7,10)

Here, the input image is parsed by every tenth line, but only the first,
seventh, and tenth starting lines (sensors) are output.


  PARSE (CH10,CH11,CH12,C13,CH14) ASTER_TIR COUNT=10 'REVERSE

In this example, a single image is regenerated from its components.  That is,
if the outputs of the first example were used as inputs for this example, the
output would be identical to the input of the first example.
WRITTEN BY:  Ron Alley   25 May 2000
COGNIZANT PROGRAMMER:  Ron Alley
REVISION:  New  25 May 2000