.. index:: ! x2sys_init .. include:: ../module_supplements_purpose.rst_ ********** x2sys_init ********** |x2sys_init_purpose| Synopsis -------- .. include:: ../../common_SYN_OPTs.rst_ **gmt x2sys_init** *TAG* |-D|\ *fmtfile* [ |-E|\ *suffix* ] [ |-F| ] [ |-G|\ [**d**\|\ **g**] ] [ |-I|\ *dx*\ [/*dy*] ] [ |-N|\ **d**\|\ **s**\ *unit* ] [ |SYN_OPT-R| ] [ |SYN_OPT-V| ] [ |-W|\ **t**\|\ **d**\ *gap* ] [ |SYN_OPT-j| ] [ |SYN_OPT--| ] |No-spaces| Description ----------- **x2sys_init** is the starting point for anyone wishing to use x2sys; it initializes a set of data bases that are particular to one kind of track data. These data, their associated data bases, and key parameters are given a short-hand notation called an x2sys TAG. The TAG keeps track of settings such as file format, whether the data are geographic or not, and the binning resolution for track indices. Running **x2sys_init** is a prerequisite to running any of the other x2sys programs, such as :doc:`x2sys_binlist`, which will create a crude representation of where each data track go within the domain and which observations are available; this information serves as input to :doc:`x2sys_put` which updates the track data base. Then, :doc:`x2sys_get` can be used to find which tracks and data are available inside a given region. With that list of tracks you can use :doc:`x2sys_cross` to calculate track crossovers, use :doc:`x2sys_report` to report crossover statistics or :doc:`x2sys_list` to pull out selected crossover information that :doc:`x2sys_solve` can use to determine track-specific systematic corrections. These corrections may be used with :doc:`x2sys_datalist` to extract corrected data values for use in subsequent work. Because you can run **x2sys_init** you *must* set the environmental parameter X2SYS_HOME to a directory where you have write permission, which is where x2sys can keep track of your settings. Required Arguments ------------------ *TAG* The unique name of this data type x2sys TAG. .. _-D: **-D**\ *fmtfile* Format definition file prefix for this data set [See Format Definition Files below for more information]. Specify full path if the file is not in the current directory. If |-D| is not given then we default to *TAG*\ .fmt. **Note**: Deprecated extension .def will work but consider renaming the file. Optional Arguments ------------------ .. _-E: **-E**\ *suffix* Specifies the file extension (suffix) for these data files. If not given we use the format definition file prefix as the suffix (see |-D|). .. _-F: **-F** Force creating new files if old ones are present [Default will abort if old TAG files are found]. .. _-G: **-G**\ [**d**\|\ **g**] Selects geographical coordinates. Append **d** for discontinuity at the Dateline (makes longitude go from -180 to + 180) or **g** for discontinuity at Greenwich (makes longitude go from 0 to 360 [Default]). If not given we assume the data are Cartesian. .. _-I: **-I**\ *dx*\ [/*dy*] *x_inc* [and optionally *y_inc*] is the grid spacing. Append **m** to indicate minutes or **s** to indicate seconds for geographic data. These spacings refer to the binning used in the track bin-index data base. .. _-N: **-Nd**\|\ **s**\ *unit* Sets the units used for distance and speed when requested by other programs. Append **d** for distance or **s** for speed, then give the desired *unit* as **c** (Cartesian userdist or userdist/usertime), **e** (meters or m/s), **f** (feet or feet/s), **k** (km or kms/hr), **m** (miles or miles/hr), **n** (nautical miles or knots) or **u** (survey feet or survey feet/s). [Default is **-Ndk** **-Nse** (km and m/s) if |-G| is set and **-Ndc** and **-Nsc** otherwise (Cartesian units)]. .. _-R: .. |Add_-Rgeo| replace:: For Cartesian data just give *xmin/xmax/ymin/ymax*. This option bases the statistics on those COE that fall inside the specified domain. .. include:: ../../explain_-Rgeo.rst_ .. |Add_-V| replace:: |Add_-V_links| .. include:: /explain_-V.rst_ :start-after: **Syntax** :end-before: **Description** **-Wt**\|\ **d**\ *gap* Give **t** or **d** and append the corresponding maximum time gap (in user units; this is typically seconds [Infinity]), or distance (for units, see |-N|) gap [Infinity]) allowed between the two data points immediately on either side of a crossover. If these limits are exceeded then a data gap is assumed and no COE will be determined. .. include:: ../../explain_distcalc.rst_ .. include:: ../../explain_help.rst_ Format Definition Files ----------------------- These \*.fmt files contain information about the data file format and have two sections: (1) header information and (2) column information. All header information starts with the character # in the first column, immediately followed by an upper-case directive. If the directive takes an argument it is separated by white-space. You may append a trailing # comments. Five directives are recognized: **ASCII** states that the data files are in ASCII format. **BINARY** states that the data files are native binary files. **NETCDF** states that the data files are COARDS-compliant 1-D netCDF files. **SKIP** takes an integer argument which is either the number of lines to skip (when reading ASCII files) or the number of bytes to skip (when reading native binary files). Not used with netCDF files. **GEO** indicates that these files are geographic data sets, with periodicities in the *x*-coordinate (longitudes). Alternatively, use |-G|. **MULTISEG** means each track consists of multiple segments separated by a GMT segment header. Not used with netCDF files. The column information consists of one line per column in the order the columns appear in the data file. For each column you must provide seven attributes: *name type NaN NaN-proxy scale offset oformat* *name* is the name of the column variable. You must use the special names *lon* (or *x* if Cartesian) and *lat* (or *y*) for the two required coordinate columns, *time* when optional absolute time data are present, and *rtime* when relative time data are given (make sure the GMT defaults :term:`TIME_UNIT` and :term:`TIME_EPOCH` are set properly). Regardless of input time flavor, we will write absolute time on output. *type* is always **a** for ASCII representations of numbers, whereas for binary files you may choose among **c** for signed 1-byte character (-127,+128), **u** for unsigned byte (0-255), **h** for signed 2-byte integers (-32768,+32767), **i** for signed 4-byte integers (-2,147,483,648,+2,147,483,647), **f** for 4-byte floating points and **d** for 8-byte double precision floating points. For netCDF, simply use **d** as netCDF will automatically handle type-conversions during reading. *NaN* is Y if certain values (e.g, -9999) are to be replaced by NaN, and N otherwise. *NaN-proxy* is that special value (e.g., -9999). *scale* is used to multiply the data after reading. *offset* is used to add to the scaled data. *oformat* is a C-style format string used to print values from this column. If you give - as the *oformat* then GMT's formatting machinery will be used instead (i.e., :term:`FORMAT_FLOAT_OUT`, :term:`FORMAT_GEO_MAP`, :term:`FORMAT_DATE_MAP`, :term:`FORMAT_CLOCK_MAP`). Some file formats already have definition files premade. These include mgd77 (for plain ASCII MGD77 data files), mgd77+ (for enhanced MGD77+ netCDF files), gmt (for old mgg supplement binary files), xy (for plain ASCII x, y tables), xyz (same, with one z-column), geo (for plain ASCII longitude, latitude files), and geoz (same, with one z-column). Examples -------- If you have a large set of track data files you can organize them using the x2sys tools. Here we will outline the steps. Let us assume that your track data file format consist of 2 header records with text information followed by any number of identically formatted data records with 6 columns (lat, lon, time, obs1, obs2, obs3) and that files are called \*.trk. We will call this the "line" format. First, we create the line.fmt file: ====== ==== === ========= ===== ====== ======== # Format define file for the line format ----------------------------------------------------- # SKIP 2 # Skip 2 header records ----------------- ---------------------------------- # GEO # Data are geographic ----------------- ---------------------------------- #name type NaN NaN-proxy scale offset oformat ====== ==== === ========= ===== ====== ======== lat a N 0 1 0 %9.5f lon a N 0 1 0 %10.5f time a N 0 1 0 %7.1f obs1 a N 0 1 0 %7.2f obs2 a N 0 1 0 %7.2f obs3 a N 0 1 0 %7.2f ====== ==== === ========= ===== ====== ======== Next we create the TAG and the TAG directory with the databases for these line track files. Assuming these contain geographic data and that we want to keep track of the data distribution at a 1 x 1 degree resolution, with distances in km calculated along geodesics and with speeds given in knots, we may run :: gmt x2sys_init LINE -V -G -Dline -Rg -je -Ndk -Nsn -I1/1 -Etrk where we have selected LINE to be our x2sys tag. When x2sys tools try to read your line data files they will first look in the current directory and second look in the file *TAG*\ \_paths.txt for a list of additional directories to examine. Therefore, create such a file (here LINE_paths.txt) and stick the full paths to your data directories there. All TAG-related files (format definition files, tag files, and track data bases created) will be expected to be in the directory pointed to by **$X2SYS_HOME**/*TAG* (in our case **$X2SYS_HOME**/LINE). Note that the argument to |-D| must contain the full path if the \*.fmt file is not in the current directory. **x2sys_init** will copy this file to the **$X2SYS_HOME**/*TAG* directory where all other x2sys tools will expect to find it. **Create tbf file(s):** Once the (empty) TAG databases have been initialized we go through a two-step process to populate them. First we run :doc:`x2sys_binlist` on all our track files to create one (or more) multisegment track bin-index files (tbf). These contain information on which 1 x 1 degree bins (or any other blocksize; see |-I|) each track has visited and which observations (in your case obs1, obs2, obs3) were actually observed (not all tracks may have all three kinds of observations everywhere). For instance, if your tracks are listed in the file tracks.lis we may run this command: :: gmt x2sys_binlist -V -TLINE =tracks.lis > tracks.tbf **Update index data base:** Next, the track bin-index files are fed to :doc:`x2sys_put` which will insert the information into the TAG databases: :: gmt x2sys_put -V -TLINE tracks.tbf **Search for data:** You may now use :doc:`x2sys_get` to find all the tracks within a certain sub-region, and optionally limit the search to those tracks that have a particular combination of observables. E.g., to find all the tracks which has both obs1 and obs3 inside the specified region, run :: gmt x2sys_get -V -TLINE -R20/40/-40/-20 -Fobs1,obs3 > tracks.tbf **MGD77[+] or GMT:** Format definition files already exist for MGD77 files (both standard ASCII and enhanced netCDF-based MGD77+ files) and the old \*.gmt files manipulated by the mgg supplements; for these data sets the **-j** and |-N| will default to great circle distance calculation in km and speed in m/s. There are also format definition files for plain (*x, y*\ [*, z*]) and (*lon, lat*\ [*, z*]) tracks. To initiate new track databases to be used with MGD77 data from NCEI, try :: gmt x2sys_init MGD77 -V -Dmgd77 -Emgd77 -Rd -Gd -Nsn -I1/1 -Wt900 -Wd5 where we have chosen a 15 minute (900 sec) or 5 km threshold to indicate a data gap and selected knots as the speed; the other steps are similar. **Binary files:** Let us pretend that your line files actually are binary files with a 128-byte header structure (to be skipped) followed by the data records and where *lon*, *lat*, *time* are double precision numbers while the three observations are 2-byte integers which must be multiplied by 0.1. Finally, the first two observations may be -32768 which means there is no data available. All that is needed is a different line.fmt file: ====== ==== === ========= ===== ====== ======== # Format define file for the binary line format ----------------------------------------------------- # BINARY # File is now binary ----------------- ---------------------------------- # SKIP 128 # Skip 128 bytes ----------------- ---------------------------------- # GEO # Data are geographic ----------------- ---------------------------------- #name type NaN NaN-proxy scale offset oformat ====== ==== === ========= ===== ====== ======== lon d N 0 1 0 %10.5f lat d N 0 1 0 %9.5f time d N 0 1 0 %7.1f obs1 h Y -32768 0.1 0 %6.1f obs2 h Y -32768 0.1 0 %6.1f obs3 h N 0 0.1 0 %6.1f ====== ==== === ========= ===== ====== ======== The rest of the steps are identical. **COARDS 1-D netCDF files:** Finally, suppose that your line files actually are netCDF files that conform to the COARDS convention, with data columns named *lon*, *lat*, *time*, *obs1*, *obs2*, and *obs3*. All that is needed is a different line.fmt file: ====== ==== === ========= ===== ====== ======== # Format define file for the netCDF COARDS line format ----------------------------------------------------- # NETCDF # File is now netCDF ----------------- ---------------------------------- # GEO # Data are geographic ----------------- ---------------------------------- #name type NaN NaN-proxy scale offset oformat ====== ==== === ========= ===== ====== ======== lon d N 0 1 0 %10.5f lat d N 0 1 0 %9.5f time d N 0 1 0 %7.1f obs1 d N 0 1 0 %6.1f obs2 d N 0 1 0 %6.1f obs3 d N 0 1 0 %6.1f ====== ==== === ========= ===== ====== ======== Note we use no scaling or NaN proxies since those issues are usually handled internally in the netCDF format description. Deprecated behavior ------------------- The Format Definition Files used to have extension .def but since that is also used by GMT's symbol macro files we have deprecated that extension and now use .fmt. However, old .def files are still being read. .. include:: x2sys_refs.rst_ See Also -------- :doc:`x2sys_binlist`, :doc:`x2sys_datalist`, :doc:`x2sys_get`, :doc:`x2sys_list`, :doc:`x2sys_put`, :doc:`x2sys_report`, :doc:`x2sys_solve`, :doc:`x2sys_cross`