
                            OBSDES DOCUMENTATION


    Obsdes v 1.8 is based on the Federal Geodetic Control Committee publi-
cation Input and Specifications of the National Geodetic Survey Data Base
(Blue Book), vol. I, chapters two and three, (1980, reprint 1982) as of
September 1986 with three digit ssns (old blue book) and the January 1989
revision with four digit ssns (new blue book or unified descriptions).

    Obsdes compares a horizontal Blue Book Description data set  with its
respective Blue Book Observation data set .  Obsdes produces a list of error
messages along with the description data set record and observation data set
information.  The latter may consist of observation data set station names,
state or country codes, and for the old blue book, measured distances and 
directions which fail to match the description *30* record observations.
End of file messages may precede the error messages and a summary of all
observation data set control point ssn's and station names for which a des-
cription or recovery note was not found may follow the error messages. 

    For the old blue book, distance information consists of record sequence
numbers, measured distances and distance codes.  Direction information
consists of sequence numbers, set numbers, visibility codes and directions.
Mark-to-mark distances are reduced to sea level and directions may be
derived from combined lists if necessary.

    It is assumed that the observation data set and description data set
have been successfully run through Chkobs and Chkdes respectively and all
syntax and structure errors have been resolved.

  INPUT

     1.  An input blue book observation data set file.
	 This may be an old blue book with three digit ssns or the
	 new blue book with four digit ssns.
         The filename is entered in the interactive mode.

     2.  An input blue book description data set file.
	 This may be the old blue book with three digit ssns or the
	 new or "unified" description blue book with four digit ssns.
         The filename is entered in the interactive mode.

  OUTPUT

     Program output error messages
     This may be printed and written to a file.  This
     output filename is entered in the interactive mode.

     This is an example of a program output from a obsdes v 1.8 run
     using the new blue book observation data set with four digit 
     ssns and the unified description data set with four digit ssns:

1 NATIONAL GEODETIC SURVEY PROGRAM OBSDES  VERSION  1.8  
  COMPARE A BLUE BOOK DESC DATA SET WITH ITS RESPECTIVE BLUE BOOK OBS DATA SET

  INPUT FILES - gps331.b                         gps331.d                      
  OUTPUT FILE - gps331.ot2                    

 000330*10*923ORMN425014W0972702393.0M 0420971 NECEDAR               P   NM1590  
 CC 11-13 SSN UNMATCHED--PROCESS NEXT 10 RECORD

 THE FOLLOWING BLUE BOOK OBS 80 OR 81 RECORDS DO NOT HAVE A DESCRIPTION
 SSN      STATION NAME

 9232     ATEN RESET                    
 8968     FAA 0D8 RWY 13                
 8969     FAA 0D8 RWY 31                
 8972     FAA 1D8 RWY 13                
 8973     FAA 1D8 RWY 31                
 8924     FAA 2D5 RWY 12                
 8925     FAA 2D5 RWY 30                
 8976     FAA 3D3 RWY 14                
 8977     FAA 3D3 RWY 32                
 8928     FAA 5ND6 RWY 16               
 8929     FAA 5ND6 RWY 34               

 PROGRAM OBSDES TERMINATED

     An unsuccessful run may occur from an I/O error and not have any
     output.  Examples of an unsuccessful run due to I/O errors:

     "ERROR IN OPENING BLUE BOOK DESC DATA SET FILE - (filename)
      EXECUTION TERMINATED"
     Possible resolution:  incorrect filename entered

     "ERROR IN OPENING BLUE BOOK OBS DATA SET FILE - (filename)
      EXECUTION TERMINATED"
     Possible resolution: incorrect filename entered

     "ERROR IN OPENING PROGRAM OUTPUT FILE - (filename)
      EXECUTION TERMINATED"
     Possible resolution:  This should be a new file and should not exist
     prior to this run, there may be a duplicate filename.

     An unsuccessful run may also occur due to incorrect observation and/
     or description data sets.  Review the CHKOBS and CHKDES runs for
     syntax and structure errors.

  EXECUTING OBSDES

     Hardware requirements:

     a.  At least one floppy disk drive and a hard disk
                         or
         two floppy disk drives.
     b.  At least 268K of main memory
     c.  The 8087 math co-processor.
     d.  A printer (80 characters/line).

     The user will be supplied with a floppy disk containing one file:
 OBSDES.EXE.  The user should load this onto the PC's hard disk (this
 need only be done once if it permanently resides there).  If you do not
 have a hard disk, put this floppy disk in your default drive.

To execute -

To turn on printer to obtain an output listing:
On an IBM/XT, hit <CTRL> and <PrtSc> keys simultaneously.

Type obsdes

"Welcome to program obsdes version 1.8"
"Enter the blue book observation filename -"

Type in the filename of the input observation data set (include disk
drive designation if it is not on the hard disk).
Example:  A:gps331.b

"Is this the new version of the blue book observation data set (y/n) ?"

Respond n for old three digit ssn blue book or y for new four digit
ssn blue book

"Enter the blue book description filename -"

Type in the filename of the input description data set.
Example:  A:gps331.d

"Is this a unified blue book description data set (y/n) ?"
Respond y or n accordingly

"Enter the program output filename -"

Type in the filename of the program output (include disk drive
designation if it is not on the hard disk).
Example: A:gps331.ot2

The program output will then exist on that specified file.  If you
want to look at the output go into the file via your editor and scan
through it.
