GFILE - SESSION HEADER RECORD
02-05 Year, First Actual Measurement (UTC) (CCYY) Alpha
06-07 Month, First Actual Measurement (UTC) (MM) Integer
08-09 Day, First Actual Measurement (UTC) (DD) Integer
10-13 Time, First Actual Measurement (UTC) (DD) Integer
14-17 Year, Last Actual Measurement (UTC) (CCYY) Integer
18-19 Month, Last Actual Measurement (UTC) (MM) Integer
20-21 Day, Last Actual Measurement (UTC) (DD) Integer
22-25 Time, First Actual Measurement (UTC) (DD) Integer
26-27 Number of Vectors in Session Integer
28-42 Software Name and Version Alpha
43-47 Orbit Source (agency that computes orbit) Alpha
48-51 Orbit accuracy estimate (XXX.x meters) Implied Decimal