Regarding the 7777 tie file:
  • A virtual check-in was created for the begining of the day, because another
    gravity check-in point was used and not visited again. To do this:
      – A Δ from datum value was calculated for the check-in used at the 
        begining of the day:
          ○ station 1112
          ○ datum                          7348.405 mGal
          ○ early day value              – 5492.4778 mGal
          ○ Δ                            = 1855.927 mGal.
      – The Δ value was then subtracted from the datum of 7777 to create 
        a virtual check-in at the time of the 1112 check-in:
          ○ station 7777
          ○ datum                          7372.619 mGal
          ○ Δ                            – 1855.927 mGal    
          ○ virtual check-in             = 5516.692 mGal

Regarding the 2 xyz files:
  • The DEM covering the whole area is very large, in fact likely too large for
    the field computer used in conjunction with Gravred 3.2 (who is systematically
    loading the whole DEM to the RAM before proceeding to calculations). So in order
    to avoid errors due to lack of memory available, the inner DEM was split into
    2 files of 5.5M points each, and the results from two individual runs are added
    together to create the final xyz containing one unique inner DEM correction value.
  • The final xyz is actually a merger of all days together.