SIGMA RECORDS

These records are used to estimate the apriori standard deviation for directions, distances or azimuths.

      COLUMN    CONTENT

          1     Blank
        2-3     SIGMA code : 51 : directions
                             52 : distances
                             53 : azimuths
        4-6     Type used to identify the instrument code and the
                observing procedure (See lists of SDA, SDB, SDC, SDO
                and SDT)
        7-14    SDA :  standard deviation estimate of:
                        51 :  a direction in seconds
                        52 :  a distance in centimeters (constant part)
                        53 :  an azimuth in seconds
       15-19    SDB :  standard deviation estimate of:
                        51 :    no SDB for direction observations
                        52 :    a distance in parts per million
                                (proportional scale)
                        53 :    the instrument levelling in seconds
       20-24    SDC :   standard deviation estimate of observed longitude
                                in seconds (for azimuth only, code 53)
       25-28    Year of survey

          29    Blank
       30-34    SDO :  standard deviation estimate for centering error
                                of originating station in centimeters
       35-39    SDT :  standard deviation estimate for centering error
                                of target station in centimeters
       40-49    Party chief or other project identifier

       50-54    Agency code
       55-72    Comments
       73-80    Auxiliary parameter identifier for distance and azimuth