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 -TMGD77
-Cfaa
-Fnc
> faa_coe.txt
x2sys_solve faa_coe.txt
-V -TMGD77
-Cfaa
-Ec
> coe_table.txt
To fit a faa linear drift with time instead, try
x2sys_list COE_data.txt
-V -TMGD77
-Cfaa
-FnTc > faa_coe.txt
x2sys_solve faa_coe.txt
-V -TMGD77
-Cfaa
-Et
> 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 -TMGD77
-Cmag
-Fnhc > mag_coe.txt
x2sys_solve mag_coe.txt
-V -TMGD77
-Cmag
-Eh
> coe_table.txt
To estimate unit scale corrections based on bathymetry crossovers, try
x2sys_list COE_data.txt
-V -TMGD77
-Cdepth
-Fnz > depth_coe.txt
x2sys_solve depth_coe.txt
-V -TMGD77
-Cdepth
-Es > 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)