x2sys_cross(tracks=None, outfile=None, **kwargs)¶
Calculate crossovers between track data files.
x2sys_cross is used to determine all intersections between (“external cross-overs”) or within (“internal cross-overs”) tracks (Cartesian or geographic), and report the time, position, distance along track, heading and speed along each track segment, and the crossover error (COE) and mean values for all observables. By default, x2sys_cross will look for both external and internal COEs. As an option, you may choose to project all data using one of the map-projections prior to calculating the COE.
Full option list at https://docs.generic-mapping-tools.org/latest/supplements/x2sys/x2sys_cross.html
A = combitable
C = runtimes
D = override
I = interpolation
Q = coe
R = region
S = speed
T = tag
V = verbose
W = numpoints
Z = trackvalues
A table or a list of tables with (x, y) or (lon, lat) values in the first two columns. Track(s) can be provided as pandas DataFrame tables or file names. Supported file formats are ASCII, native binary, or COARDS netCDF 1-D data. More columns may also be present.
If the filenames 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).
outfile (str) – Optional. The file name for the output ASCII txt file to store the table in.
tag (str) – Specify the x2sys TAG which identifies the attributes of this data type.
combitable (str) – Only process the pair-combinations found in the file combitable [Default process all possible combinations among the specified files]. The file combitable is created by x2sys_get’s -L option
runtimes (bool or str) – Compute and append the processing run-time for each pair to the progress message (use
runtimes=True). Pass in a filename (e.g.
runtimes="file.txt") to save these run-times to file. The idea here is to use the knowledge of run-times to split the main process in a number of sub-processes that can each be launched in a different processor of your multi-core machine. See the MATLAB function split_file4coes.m that lives in the x2sys supplement source code.
override (bool or str) – S|N. Control how geographic coordinates are handled (Cartesian data are unaffected). By default, we determine if the data are closer to one pole than the other, and then we use a cylindrical polar conversion to avoid problems with longitude jumps. You can turn this off entirely with override and then the calculations uses the original data (we have protections against longitude jumps). However, you can force the selection of the pole for the projection by appending S or N for the south or north pole, respectively. The conversion is used because the algorithm used to find crossovers is inherently a Cartesian algorithm that can run into trouble with data that has large longitudinal range at higher latitudes.
interpolation (str) –
l|a|c. Sets the interpolation mode for estimating values at the crossover. Choose among:
l - Linear interpolation [Default].
a - Akima spline interpolation.
c - Cubic spline interpolation.
coe (str) – Use e for external COEs only, and i for internal COEs only [Default is all COEs].
l|u|hspeed. Defines window of track speeds. If speeds are outside this window we do not calculate a COE. Specify:
l sets lower speed [Default is 0].
u sets upper speed [Default is Infinity].
h does not limit the speed but sets a lower speed below which
headings will not be computed (i.e., set to NaN) [Default calculates headings regardless of speed].
For example, you can use
speed=["l0", "u10", "h5"]to set a lower speed of 0, upper speed of 10, and disable heading calculations for speeds below 5.
Select verbosity level [Default is w], which modulates the messages written to stderr. Choose among 7 levels of verbosity:
q - Quiet, not even fatal error messages are produced
e - Error messages only
w - Warnings [Default]
t - Timings (report runtimes for time-intensive algorthms);
i - Informational messages (same as
c - Compatibility warnings
d - Debugging messages
numpoints (int) – Give the maximum number of data points on either side of the crossover to use in the spline interpolation [Default is 3].
trackvalues (bool) – Report the values of each track at the crossover [Default reports the crossover value and the mean value].
crossover_errors (pandas.DataFrame or None) – Table containing crossover error information. Return type depends on whether the outfile parameter is set:
pandas.DataFrame table with (x, y, …, etc) if outfile is not set
None if outfile is set (track output will be stored in outfile)