This file defines the columns of data in attitude2.log files. Each line of
each attitude2d.log file contains a precise two-dimensional attitude solution
for a constrained-length two-antenna baseline. See channel.txt for a
definition of ORT; note that ORT is close enough to true GPS time for the
difference to be ignored in many use cases of these attitude solutions.

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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 baseline vector between the two antennas expressed in 
              meters in 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 ---------- Group identifier of reference antenna on rover platform. See
              SignalType::Group in signaltype.h.

18 ---------- Group identifier of rover antenna on rover platform. See
              SignalType::Group in signaltype.h.

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