User's Guide

SUBREGIONS

Generate a subset of an orbital stitch list

Function:

Generate a subset of an orbital stitch list by limiting the output to specified GOODES projection region(s).

Parameters:

INFILE
Input file. The file containing the list of orbital data. Refer to User Note 1 for the format of this file.

OUTFILE
Output file. The output file containing the list of orbital data. Refer to User Note 2 for the format of this file.

REGIONS
Regions of interest. The global GOODES projection regions that are to be used to select scenes to be written to OUTFILE. Refer to User Note 4 for the definition of these regions.

ORBFLG("NO")
Orbit flag. Flag to determine whether to print an orbit with only one input scene which is already a stitched orbit.


    YES:  Print an orbit which consists of one input scene
	  which is already a stitched orbit.
    NO:   Don't print an orbit which consists of only one
	  input scene which is already a stitched orbit.

Example:

  1. LAS> subregions infile=ss040110;txt outfile=ss040110;reg regions=1,3,6,10

    The input scenes from file "ss040110;txt" are grouped into half orbits. All of the information associated with each half orbit is written to "ss040110;reg" if any of the input scenes within the half orbit lie within region 1, 3, 6, or 10.

Description/Algorithm:

Read the input orbital stitch file and store all of the data associated with one half orbit. For all of the input scenes within the half orbit, determine which of the global GOODES regions lie at least partially within the scenes. Print the data lines for the entire half orbit to the output file if any of the regions found within the input images match the region numbers specified by the user. If no region numbers within the half orbit match those specified by the user, disregard the entire half orbit of data and proceed to the next half orbit. Continue reading from the input orbital stitch file and writing to the output orbital stitch file until the entire input file has been processed.

Nonfatal Error Message:

    None.

Fatal Error Messages:

  1. [subregions-fatal] Fatal error encountered

    A fatal error was encountered. The message preceding this message is the specific error encountered.

  2. [subregions-dcon] Error converting date

    An error occurred while converting a scene acquisition date to a julian date. Check the input file for invalid acquisition dates.

  3. [subregions-numscene] Too many scenes for half orbit, currently limited to <XX> The number of scenes listed for a half orbit exceeded the current limit. Reduce the number of scenes in the list for the particular half orbit and rerun. Contact the system administrator if the limit needs to be increased.

  4. [subregions-open] Error opening input file

    An error occurred while attempting to open the input file. Verify the file exists with the proper permission.

  5. [subregions-head] Error reading header in input file

    An error occurred attempting to read the header in the input file. Make certain the header matches the header described in User Note 1.

  6. [subregions-lock] Error locking the output file

    An error occurred locking the output file for exclusive write permission. Verify the file permissions.

  7. [subregions-skip] Error skipping to end of the file

    An error occurred skipping to the end of the output file. Examine the contents of the output file.

  8. [subregions-unlck] Error unlocking the file

    An error occurred unlocking the output file. Verify the file permissions.

User Notes:

  1. The expected format of the input file is as follows:

    
        tapeid mth acqdate  start  stop ceos st d a source flg
        031185 AH 04/01/92   5332  10408 NGC 11 D A  31376
        019990 AH 04/01/92  34636  35718 HBT 11 D A  37446
        020403 AH 04/01/92  35703  40438 TSV 11 D A  38496
        031272 AL 04/01/92  41800  42906 NOA 11 D A  31435
        019990 AH 04/01/92  52626  54118 HBT 11 D A  37447
        020403 AH 04/01/92  53416  54728 TSV 11 D A  38497
                 .                            .
                 .                            .
                 .                            .
    
    
    The input file is read until the header line beginning with "tapeid" is encountered. All subsequent lines are expected to be in the above format. The file may be generated by LISTITCH or it may be generated directly from the AVHRR database.

  2. The format of the output file is as follows:

    
        tapeid mth acqdate  start  stop ceos st d a source flg
    
        031185 AH 04/01/92   5332  10408 NGC 11 D A  31376
    
        019990 AH 04/01/92  34636  35718 HBT 11 D A  37446
        020403 AH 04/01/92  35703  40438 TSV 11 D A  38496
        031272 AL 04/01/92  41800  42906 NOA 11 D A  31435
    
        019990 AH 04/01/92  52626  54118 HBT 11 D A  37447
        020403 AH 04/01/92  53416  54728 TSV 11 D A  38497
                 .                            .
                 .                            .
                 .                            .
    
    
    Note that the format of the output file is the same as the format of the input file except that it separates half orbits with blank lines. These blank lines are added only to make the file more readable.

  3. The user may want to specify all 12 regions to generate an output list that is the same as the input list except that the output list will contain a blank line between each half orbit.
  4. The 12 regions are defined by the global GOODES projection as follows (in degrees):

    
        region number   min latitude   max latitude   min longitude   max longitude
        1                40.73333        90.            -180.           -40.
        2                40.73333        90.             -40.           180.
        3                 0.             40.73333       -180.           -40.
        4                 0.             40.73333        -40.           180.
        5               -40.73333         0.            -180.          -100.
        6               -40.73333         0.            -100.           -20.
        7               -40.73333         0.             -20.            80.
        8               -40.73333         0.              80.           180.
        9               -90.            -40.73333       -180.          -100.
        10              -90.            -40.73333       -100.           -20.
        11              -90.            -40.73333        -20.            80.
        12              -90.            -40.73333         80.           180.
    
    

  5. As an "after the fact" modification, the ORBFLG parameter was added to SUBREGIONS. This parameter allows the user to not write out a half orbit which consist of one input scene which has already been stitched.

  6. Refer to the orbital stitching overview for more detailed information.