gmtconvert(cmd0::String="", arg1=nothing, kwargs...)



Can do a combination of nine tasks: (1) convert between binary and ASCII data tables, (2) paste corresponding records from multiple files horizontally into a single file, (3) extract a subset of the available columns, (4) only extract segments whose header record matches a text pattern search, (5) only list segment headers and no data records, (6) extract first and/or last data record for each segment, (7) reverse the order of items on output, (8) output only ranges of segment numbers, and (9) output only segments whose record count matches criteria. Input (and hence output) may have multiple sub-headers, and ASCII tables may have regular headers as well.

Required Arguments

  • table
    One or more data tables holding a number of data columns.

Optional Arguments

  • A or hcat : – hcat=true
    The records from the input files should be pasted horizontally, not appended vertically [Default]. All files must have the same number of segments and number of rows per segment. Note for binary input, all the files you want to paste must have the same number of columns (as set with -bi); ASCII tables can have different number of columns.

  • C or n_records : – n_records=[+l\min][+u\max][+i]
    Only output segments whose number of records matches your given criteria: Append +l\min to ensure all segment must have at least min records to be written to output [0], and append +u\max to ensure all segments must have at most max records to be written [inf]. You may append +i to invert the selection, i.e., only segments with record counts outside the given range will be output.

  • D or dump : – dump=[template\ [+o\orig]]
    For multiple segment data, dump each segment to a separate output file [Default writes a multiple segment file to standard output]. Append a format template for the individual file names; this template must contain a C format specifier that can format an integer argument (the running segment number across all tables); this is usually %d but could be %08d which gives leading zeros, etc. [Default is gmtconvert_segment_%d.{txt\|bin}, depending on -bo]. Append +o\orig to start the numbering from orig instead of zero. Alternatively, give a template with two C format specifiers and we will supply the table number and the segment number within the table to build the file name. Append +o\torig\ /sorig to start the numbering of tables from torig and numbering of segments within a table from sorig instead of zero. The +o modifier will be stripped off before the template is used.

  • E or first_last : – first_last=[f|l|m|M *stride]
    Only extract the first and last record for each segment of interest [Default extracts all records]. Optionally, append f or l to only extract the first or last record of each segment, respectively. Alternatively, append m\
    stride* to extract every stride records; use M to also include the last record.

  • F or conn_method : – conn_method=[c|n|p|v][**a|t|s|r| *refpoint]
    Alter the way points are connected (by specifying a *scheme
    ) and data are grouped (by specifying a method). Append one of four line connection schemes:

    • c : Form continuous line segments for each group [Default].

    • p : Form line segments from a reference point reset for each group.

    • n : Form networks of line segments between all points in each group.

    • v : Form vector line segments suitable for :doc:plot-Sv+s.

    Optionally, append the one of four segmentation methods to define the group:

    • a : Ignore all segment headers, i.e., let all points belong to a single group,

    and set group reference point to the very first point of the first file.

    • t : Consider all data in each table to be a single separate group and reset the group reference point to the first point of each group.

    • s : Segment headers are honored so each segment is a group; the group

    reference point is reset to the first point of each incoming segment [Default].

    • r : Same as s, but the group reference point is reset after each record to the previous point (this method is only available with the Fp scheme).

Instead of the codes **a|f|s|r** you may append the coordinates of a *refpoint* which will serve as a fixed external reference point for all groups.

  • I or invert or reverse : – invert=true | invert=:tsr
    Invert the order of items, i.e., output the items in reverse order, starting with the last and ending up with the first item [Default keeps original order]. Append up to three items that should be reversed: t will reverse the order of tables, s will reverse the order of segments within each table, and r will reverse the order of records within each segment [Default].

  • L or list_only : – list_only=true
    Only output a listing of all segment header records and no data records (requires ASCII data).

  • N or sort : – sort=col* [+a|d]
    Numerically sort each segment based on values in column *col
    . The data records will be sorted such that the chosen column will fall into ascending order [+a, which is Default]. Append +d to sort into descending order instead. The sort option can be combined with any other ordering scheme except conn_method (segmentation) and is applied at the end.

  • Q or segments : – segments=[~]\selection*
    Only write segments whose number is included in *selection
    and skip all others. Cannot be used with |-S|. The selection syntax is range[,range,...] where each range of items is either a single segment number or a range with stepped increments given via start\ [:step:]\ :stop (step is optional and defaults to 1). A leading ~ will invert the selection and write all segments but the ones listed. Instead of a list of ranges, use +f file to supply a file list with one range per line.

  • S or select_hdr : – select_hdr=[~]\"search string"\|\+f\|\file\ [+e] \| |-S|\ [~]/\regexp/[i][+e]
    Only output those segments whose header record contains the specified text string. To reverse the search, i.e., to output segments whose headers do not contain the specified pattern, use select_hdr=:~. Should your pattern happen to start with ~ you need to escape this character with a backslash [Default output all segments]. Cannot be used with |-Q|. For matching segments based on aspatial values (via OGR/GMT format), give the search string as varname\ =\value and we will compare value against the value of varname for each segment. Note: If the features are polygons then a match of a particular polygon perimeter also means that any associated polygon holes will also be matched. For matching segment headers against extended regular expressions enclose the expression in slashes. Append i for case-insensitive matching. For a list of such patterns, give +f\file with one pattern per line. To give a single pattern starting with "+f", escape it with a backslash. Finally, append +e as last modifier to request an exact match [Default will match any sub-string in the target].

  • T or skip : – skip=[h][d\ [[~]\selection]]
    Suppress the writing of certain records on output. Append h to suppress segment headers [Default], and/or d to suppress duplicate data records. Use skip=:hd to suppress both types of records. By default, all columns must be identical across the two records to skip the record. Alternatively, append a column selection to only use those columns in the comparisons instead. The selection syntax is range\ [,\range,...] where each range of items is either a single column number or a range with stepped increments given via start\ [:step:]\ :stop (step is optional and defaults to 1). A leading ~ will invert the selection and select all columns but the ones listed. To add the trailing text to the comparison as well, add the column t to the list. If no numerical columns are specified, just t, then we only consider trailing text.

  • V or verbose : – verbose=true | verbose=level
    Select verbosity level. More at verbose

  • W or word2num : – word2num=true | word2num="+n"
    Attempt to convert each word in the trailing text to a number and append such values to the numerical output columns. Text that cannot be converted (because they are not numbers) will appear as NaNs. Use modifier +n to exclude the columns with NaNs. Note: These columns are identified based on the first input record only.

  • a or aspatial : – aspatial=??
    Control how aspatial data are handled in GMT during input and output. More at

  • bi or binary_in : – binary_in=??
    Select native binary format for primary table input. More at

  • bo or binary_out : – binary_out=??
    Select native binary format for table output. More at

  • di or nodata_in : – nodata_in=??
    Substitute specific values with NaN. More at

  • e or pattern : – pattern=??
    Only accept ASCII data records that contain the specified pattern. More at

  • f or colinfo : – colinfo=??
    Specify the data types of input and/or output columns (time or geographical data). More at

  • g or gap : – gap=??
    Examine the spacing between consecutive data points in order to impose breaks in the line. More at

  • h or header : – header=??
    Specify that input and/or output file(s) have n header records. More at

  • i or incol or incols : – incol=col_num | incol="opts"
    Select input columns and transformations (0 is first column, t is trailing text, append word to read one word only). More at incol

  • j or metric or spherical_dist or spherical : – metric=greatcirc or spherical=:flat or spherical=:ellipsoidal
    Determine how spherical distances are calculated in modules that support this [Default is spherical=:greatcirc]. GMT has different ways to compute distances on planetary bodies:

- spherical=:greatcirc to perform great circle distance calculations, with parameters such as distance increments or radii compared against calculated great circle distances [Default is spherical=:greatcirc]. - spherical=:flat to select Flat Earth mode, which gives a more approximate but faster result. - spherical=:ellipsoidal to select ellipsoidal (or geodesic) mode for the highest precision and slowest calculation time. Note: All spherical distance calculations depend on the current ellipsoid (PROJ_ELLIPSOID), the definition of the mean radius (PROJ_MEAN_RADIUS), and the specification of latitude type (PROJ_AUX_LATITUDE). Geodesic distance calculations is also controlled by method (PROJ_GEODESIC).

  • q or inrows : – inrows=??
    Select specific data rows to be read and/or written. More at

  • s or skiprows or skip_NaN : – skip_NaN=true | skip_NaN="<cols[+a][+r]>"
    Suppress output of data records whose z-value(s) equal NaN. More at

  • w or wrap or cyclic : – wrap=??
    Convert input records to a cyclical coordinate. More at

  • yx : – yx=true
    Swap 1st and 2nd column on input and/or output. More at


To convert the binary file test.b (single precision) with 4 columns to ASCII:

convert("test.b", bi="4f", save="test.dat")

To convert the multiple segment ASCII table test.txt to a double precision binary file:

convert("test.txt", b=:o, save="test.b")

If the file instead is the binary file results.b which has 9 single-precision values per record, we extract the last column and columns 4-6 with the command:

D = convert("results.b", outcol="8,4-6", binary_in="9s")

To extract all segments in the file big_file.txt whose headers contain the string "RIDGE AXIS", try:

D = convert("big_file.txt", select_hdr="RIDGE AXIS")

To only get the segments in the file big_file.txt whose headers exactly matches the string "Spitsbergen", try:

D = convert("big_file.txt", select_hdr="Spitsbergen+e")

To invert the selection of segments whose headers begin with "profile " followed by an integer number and any letter between "g" and "l", try:

D = convert(select_hdr="~\"/^profile [0-9]+[g-l]$/\"")

To reverse the order of segments in a file without reversing the order of records within each segment, try:

convert("lots_of_segments.txt", invert=:s)

To extract segments 20 to 40 in steps of 2, plus segment 0 in a file, try:

convert("lots_of_segments.txt", segments="0,20:2:40")

To extract the attribute ELEVATION from an ogr gmt file like this:

    # @Tdouble|double|double
    # @D4.945000|-106500.00000000|-32700.00000000
    -9.36890245902635 39.367156766570389


D = convert("file.gmt", aspatial="ELEVATION")

To connect all points in the file sensors.txt with the specified origin at 23.5/19, try:

Dlines = convert("sensors.txt", conn_method=(23.5,19))

To write all segments in the two files A.txt and B.txt to individual files named profile005000.txt, profile005001.txt, etc., where we reset the origin of the sequential numbering from 0 to 5000, try:

convert("A.txt", "B.txt", D="profile_%6.6d.txt+o5000")

To only read rows 100-200 and 500-600 from file junk.txt, try:

D = convert("junk.txt", q="100-200,500-600")

To get all rows except those bad ones between rows 1000-2000, try:

D = convert("junk.txt", q="~1000-2000")

See Also

gmtinfo, gmtselect