============================ sbrtkdef.txt ===================================
This file defines the columns of data in the sbrtk.log files produced by the
GRID software receiver. Each sbrtk.log file contains time-stamped precise
position solutions that represent the receiver's best estimate of the
antenna's L1 phase center in ECEF coordinates. ORT time stamps indicate the
time at which the position solution applies. See channeldef.txt for a
definition of ORT.
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Column        Quantity

1 ----------- ORT week number. 

2 ----------- ORT whole seconds of week.

3 ----------- ORT fractional second. 

4,5,6 ------- X,Y,Z receiver antenna L1 phase center position expressed in
              meters the ECEF reference frame.

7-12 -------- Upper-triangular elements of the formal error covariance matrix
              P associated with the X, Y, and Z coordinates, in units of
              meters^2, in the following order: P11, P12, P13, P22, P23, P33.
              Note that the values in P are a lower bound on the actual error
              covariance, as they are output under the assumption that any
              fixed solution that has passed the integer validation test is
              based on the correct integer solution, whereas this is not
              always the case.

13 ---------- The integer ambiguity validation test statistic.  A large
              statistic (e.g., above 20) indicates a confident solution.
              Bounds on the probability of incorrect fix can be determined
              from this statistic and from the satellite geometry and number
              of participating satellites.  The test statistic by default is
              produced by application of the difference test described in
              Wang, Lei, and Sandra Verhagen. "A new ambiguity acceptance test
              threshold determination method with controllable failure rate."
              Journal of Geodesy 89.4 (2015): 361-375.
 
14 ---------- The number of double-difference measurements that participated
              in the solution at the current epoch. 

15 ---------- A flag indicating whether the integer-constrained solution
              passed the integer ambiguity validation test for the
              user-configured false fixing rate.

16 ---------- A flag indicating whether the X, Y, and Z coordinates correspond
              to an integer-fixed (1) or float (0) solution.

17 ---------- The age of reference data, in seconds.  If this is larger than 5
              seconds or so, signicant errors can arise when extrapolating the
              reference data to the current epoch.

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