Extract content of track data files
Note: No space is allowed between the option flag and the associated arguments.
x2sys_datalist reads one or more files and produces a single ASCII [or binary] table. The files can be of any format; this information is encoded in the TAG set with the -T option. You may limit the output to a geographic region, and insist that the output from several files be separated by a multiple segment header. Only the named data fields will be output [Default selects all columns].
- Can be one or more ASCII, native binary, or COARDS netCDF 1-D data files. To supply the data files via a text file with a list of tracks (one per record), specify the name of the track list after a leading equal-sign (e.g., =tracks.lis). If the names are missing their file extension we will append the suffix specified for this TAG. Track files will be searched for first in the current directory and second in all directories listed in $X2SYS_HOME/TAG/TAG_paths.txt (if it exists). [If $X2SYS_HOME is not set it will default to $GMT_SHAREDIR/x2sys]. (Note: MGD77 files will also be looked for via MGD77_HOME/mgd77_paths.txt and *.gmt files will be searched for via $GMT_SHAREDIR/mgg/gmtfile_paths).
- Specify the x2sys TAG which identifies the attributes of this data type.
- Eliminate COEs by distributing the COE between the two tracks in proportion to track weight. These (dist, adjustment) spline knots files for each track and data column are called track.column.adj and are expected to be in the $X2SYS_HOME/TAG directory. The adjustments are only applied if the corresponding adjust file can be found [No residual adjustments]
- Enhance ASCII output by writing GMT segment headers between data from each track [no segment headers].
- Give a comma-separated sub-set list of column names defined in the format definition file. [Default selects all data columns].
- Name of ASCII file with a list of track names (one per record) that should be excluded from consideration [Default includes all tracks].
- Apply optimal corrections to columns where such corrections are available. Append the correction table to use [Default uses the correction table TAG_corrections.txt which is expected to reside in the $X2SYS_HOME/TAG directory]. For the format of this file, see CORRECTIONS below.
- west, east, south, and north specify the region of interest, and you may specify them in decimal degrees or in [±]dd:mm[:ss.xxx][W|E|S|N] format Append +r if lower left and upper right map coordinates are given instead of w/e/s/n. The two shorthands -Rg and -Rd stand for global domain (0/360 and -180/+180 in longitude respectively, with -90/+90 in latitude). Set geographic regions by specifying ISO country codes from the Digital Chart of the World using -Rcode1,code2,…[+r|R[incs]] instead: Append one or more comma-separated countries using the 2-character ISO 3166-1 alpha-2 convention. To select a state of a country (if available), append .state, e.g, US.TX for Texas. To specify a whole continent, prepend = to any of the continent codes AF (Africa), AN (Antarctica), AS (Asia), EU (Europe), OC (Oceania), NA (North America), or SA (South America). Use +r to modify the bounding box coordinates from the polygon(s): Append inc, xinc/yinc, or winc/einc/sinc/ninc to adjust the region to be a multiple of these steps [no adjustment]. Alternatively, use +R to extend the region outward by adding these increments instead [no extension]. Alternatively for grid creation, give Rcodelon/lat/nx/ny, where code is a 2-character combination of L, C, R (for left, center, or right) and T, M, B for top, middle, or bottom. e.g., BL for lower left. This indicates which point on a rectangular region the lon/lat coordinate refers to, and the grid dimensions nx and ny with grid spacings via -I is used to create the corresponding region. Alternatively, specify the name of an existing grid file and the -R settings (and grid spacing, if applicable) are copied from the grid. Appending +uunit expects projected (Cartesian) coordinates compatible with chosen -J and we inversely project to determine actual rectangular geographic region. For perspective view (-p), optionally append /zmin/zmax. In case of perspective view (-p), a z-range (zmin, zmax) can be appended to indicate the third dimension. This needs to be done only when using the -Jz option, not when using only the -p option. In the latter case a perspective view of the plane is plotted, with no third dimension. For Cartesian data just give xmin/xmax/ymin/ymax. This option limits the COEs to those that fall inside the specified domain.
- Suppress output records where all the data columns are NaN [Default will output all records].
- -V[level] (more …)
- Select verbosity level [c].
- -bo[ncols][type] (more …)
- Select native binary output.
- -donodata (more …)
- Replace output columns that equal NaN with nodata.
- -h[i|o][n][+c][+d][+rremark][+rtitle] (more …)
- Skip or produce header record(s).
- -^ or just -
- Print a short message about the syntax of the command, then exits (NOTE: on Windows just use -).
- -+ or just +
- Print an extensive usage (help) message, including the explanation of any module-specific option (but not the GMT common options), then exits.
- -? or no arguments
- Print a complete usage (help) message, including the explanation of all options, then exits.
- Temporarily override a GMT default setting; repeatable. See gmt.conf for parameters.
To extract all data from the old-style MGG supplement file c2104.gmt, recognized by the tag GMT:
gmt x2sys_datalist c2104.gmt -TGMT > myfile
To make lon,lat, and depth input for blockmean and surface using all the files listed in the file tracks.lis and defined by the tag TRK, but only the data that are inside the specified area, and make output binary, run
gmt x2sys_datalist =tracks.lis -TTRK -Flon,lat,depth -R40/-30/25/35 -bo > alltopo_bin.xyz
The correction table is an ASCII file with coefficients and parameters needed to carry out corrections. This table is usually produced by x2sys_solve. Comment records beginning with # are allowed. All correction records are of the form
trackID observation correction
where trackID is the track name, observation is one of the abbreviations for an observed field contained in files under this TAG, and correction consists of one or more white-space-separated terms that will be subtracted from the observation before output. Each term must have this exact syntax:
where terms in brackets are optional (the brackets themselves are not used but regular parentheses must be used exactly as indicated). No spaces are allowed except between terms. The factor is the amplitude of the basis function, while the optional function can be one of sin, cos, or exp. The optional scale and origin can be used to translate the argument (before giving it to the optional function). The argument abbrev is one of the abbreviations for columns known to this TAG. However, it can also be one of the three auxiliary terms dist (for along-track distances), azim for along-track azimuths, and vel (for along-track speed); these are all sensitive to the -C and -N settings used when defining the TAG; furthermore, vel requires time to be present in the data. If origin is given as T it means that we should replace it with the value of abbrev for the very first record in the file (this is usually only done for time). If the first data record entry is NaN we revert origin to zero. Optionally, raise the entire expression to the given power, before multiplying by factor. The following is an example of fictitious corrections to the track ABC, implying the z column should have a linear trend removed, the field obs should be corrected by a strange dependency on latitude, weight needs to have 1 added (hence correction is given as -1), and fuel should be reduced by a linear distance term:
ABC z 7.1 1e-4*((time-T))
ABC obs 0.5*exp(-1e-3(lat))^1.5
ABC weight -1
ABC fuel 0.02*((dist))