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X2SYS_SOLVE(1)               Generic Mapping Tools              X2SYS_SOLVE(1)

NAME
       x2sys_solve - Determine systematic corrections from crossovers

SYNOPSIS
       x2sys_solve -Ccolumn -TTAG -Emode [ COE_list.d ] [ -V ] [ -W ] [ -Z ] [
       -bi[s|S|d|D[ncol]|c[var1/...]] ]

DESCRIPTION
       x2sys_solve will use the supplied crossover information to solve for
       systematic corrections that can then be applied per track to improve
       data quality. Several systematic corrections can be solved for using a
       least-squares approach.  Note: Only one data column can be processed at
       the time.

       -T     Specify the x2sys TAG which tracks the attributes of this data
              type.

       -C     Specify which data column you want to process.  Needed for
              proper formatting of the output correction table and must match
              the same option used in x2sys_list when preparing the input
              data.

       -E     The correction type you wish to model.  Choose among the
              following functions f(p), where p are the m parameters per track
              that we will fit simultaneously using a least squares approach:
              c will fit f(p) = a (a constant offset); records must contain
              cruise ID1, ID2, COE.
              d will fit f(p) = a + b * d (linear drift; d is distance;
              records must contain cruise ID1, ID2, d1, d2, COE.
              g will fit f(p) = a + b sin(y)^2  (1980-1930 gravity
              correction); records must contain cruise ID1, ID2, latitude y,
              COE.
              h will fit f(p) = a + b cos(H) + c cos(2H) + d sin(H) + e
              sin(2H) (magnetic heading correction); records must contain
              cruise ID1, ID2, heading H, COE.
              s will fit f(p) = a * z (a unit scale correction); records must
              contain cruise ID1, ID2, z1, z2.
              t will fit f(p) = a + b * (t - t0) (linear drift; t0 is the
              start time of the track); records must contain cruise ID1, ID2,
              t1-t0, t2-t0, COE.

OPTIONS
       No space between the option flag and the associated arguments.

       COE_list.d
              Name of file with the required crossover columns as produced by
              x2sys_list.  NOTE: If -bi is used then the first two columns are
              expected to hold the integer track IDs; otherwise we expect
              those columns to hold the text string names of the two tracks.

       -V     Selects verbose mode, which will send progress reports to stderr
              [Default runs "silently"].

       -W     Means that each input records has an extra column with the
              composite weight for each crossover record.  These are used to
              obtain a weighted least squares solution [no weights].

       -Z     For -Ed and -Et, determine the earliest time or shortest
              distance for each track, then use these values as the local
              origin for time duration or distance calculations.  The local
              origin is then included in the correction table [Default uses
              0].

       -bi    Selects binary input.  Append s for single precision [Default is
              d (double)].  Uppercase S or D will force byte-swapping.
              Optionally, append ncol, the number of columns in your binary
              input file if it exceeds the columns needed by the program.  Or
              append c if the input file is netCDF. Optionally, append
              var1/var2/... to specify the variables to be read.

EXAMPLES
       To fit a simple bias offset to faa for all tracks under the MGD77 tag,
       try

       x2sys_list COE_data.txt -V -T MGD77 -C faa -F nc  > faa_coe.txt
       x2sys_solve faa_coe.txt -V -T MGD77 -C faa -E c > coe_table.txt

       To fit a faa linear drift with time instead, try

       x2sys_list COE_data.txt -V -T MGD77 -C faa -F nTc  > faa_coe.txt
       x2sys_solve faa_coe.txt -V -T MGD77 -C faa -E t > coe_table.txt

       To estimate heading corrections based on magnetic crossovers associated
       with the tag MGD77 from the file COE_data.txt, try

       x2sys_list COE_data.txt -V -T MGD77 -C mag -F nhc > mag_coe.txt
       x2sys_solve mag_coe.txt -V -T MGD77 -C mag -E h > coe_table.txt

       To estimate unit scale corrections based on bathymetry crossovers, try

       x2sys_list COE_data.txt -V -T MGD77 -C depth -F nz > depth_coe.txt
       x2sys_solve depth_coe.txt -V -T MGD77 -C depth -E s > coe_table.txt

SEE ALSO
       x2sys_binlist(1), x2sys_cross(1), x2sys_datalist(1), x2sys_get(1),
       x2sys_init(1), x2sys_list(1), x2sys_put(1), x2sys_report(1)

GMT 4.5.14                        1 Nov 2015                    X2SYS_SOLVE(1)