xenial (1) gmtconnect.1gmt.gz

NAME

       gmtconnect - Connect individual lines whose end points match within tolerance

SYNOPSIS

       gmtconnect [ table ] [ [closed] ] [ [template] ] [ [linkfile] ] [ [template] ] [ [cutoff[unit][/nn_dist]]
       ] [ [level] ] [ -b<binary> ] [ -d<nodata> ] [ -f<flags> ] [ -g<gaps> ] [ -h<headers> ] [  -i<flags>  ]  [
       -o<flags> ] [ -:[i|o] ]

       Note: No space is allowed between the option flag and the associated arguments.

DESCRIPTION

       gmtconnect  reads standard input or one or more data files, which may be multisegment files, and examines
       the coordinates of the end points of all line segments. If a pair of end points are identical  or  closer
       to each other than the specified separation tolerance then the two line segments are joined into a single
       segment. The process repeats until all the remaining endpoints no longer pass  the  tolerance  test;  the
       resulting  segments  are then written out to standard output or specified output file. If it is not clear
       what the separation tolerance should be then use -L to get a list of all separation distances and analyze
       them to determine a suitable cutoff.

REQUIRED ARGUMENTS

       None.

OPTIONAL ARGUMENTS

       table  One  or  more  ASCII (or binary, see -bi[ncols][type]) data table file(s) holding a number of data
              columns. If no tables are given then we read from standard input.

       -C[closed]
              Write all the closed polygons to closed [gmtconnect_closed.txt] and all other segments as they are
              to  stdout. No connection takes place. Use -Tcutoff to set a minimum separation [0], and if cutoff
              is > 0 then we also explicitly close the polygons on output.

       -D[template]
              For multiple segment data, dump each segment to a separate output file [Default  writes  a  single
              multiple segment file]. Append a format template for the individual file names; this template must
              contain a C format specifier that can format an integer argument (the  segment  number);  this  is
              usually  %d  but could be %08d which gives leading zeros, etc. Optionally, it may also contain the
              format %c before the integer; this will then be replaced by C (closed) or  O  (open)  to  indicate
              segment type. [Default is gmtconnect_segment_%d.txt]. Note that segment headers will be written in
              either case. For composite segments, a generic segment header will  be  written  and  the  segment
              headers of individual pieces will be written out as comments to make it possible to identify where
              the connected pieces came from.

       -L[linkfile]
              Writes the link information to the specified file [gmtconnect_link.txt]. For each segment we write
              the  original  segment  id, and for the beginning and end point of the segment we report the id of
              the closest segment, whether it is the beginning (B) or end (E) point that  is  closest,  and  the
              distance between those points in units determined by -T.

       -Q[template]
              Used  with  -D  to a list file with the names of the individual output files. Optionally, append a
              filename template for the individual file names; this template may contain a  C  format  specifier
              that   can  format  an  character  (C  or  O  for  closed  or  open,  respectively).  [Default  is
              gmtconnect_list.txt].

       -T[cutoff[unit][/nn_dist]]
              Specifies the separation tolerance in the data coordinate units [0];  append  distance  unit  (see
              UNITS).  If  two  lines  has  end-points  that  are  closer  than this cutoff they will be joined.
              Optionally, append /nn_dist which adds the requirement that a link will only be made if the second
              closest  connection  exceeds  the  nn_dist. The latter distance must be given in the same units as
              cutoff.  However, if no arguments are given then we close every  polygon  regardless  of  the  gap
              between first and last point.

       -V[level] (more ...)
              Select verbosity level [c].

       -bi[ncols][t] (more ...)
              Select native binary input. [Default is 2 input columns].

       -bo[ncols][type] (more ...)
              Select native binary output. [Default is same as input].

       -d[i|o]nodata (more ...)
              Replace input columns that equal nodata with NaN and do the reverse on output.

       -f[i|o]colinfo (more ...)
              Specify data types of input and/or output columns.

       -g[a]x|y|d|X|Y|D|[col]z[+|-]gap[u] (more ...)
              Determine data gaps and line breaks.

       -h[i|o][n][+c][+d][+rremark][+rtitle] (more ...)
              Skip or produce header record(s).

       -icols[l][sscale][ooffset][,...] (more ...)
              Select input columns (0 is first column).

       -ocols[,...] (more ...)
              Select output columns (0 is first column).

       -:[i|o] (more ...)
              Swap 1st and 2nd column on input and/or output.

       -^ or just -
              Print a short message about the syntax of the command, then exits (NOTE: on Windows use just -).

       -+ 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 options, then exits.

       --version
              Print GMT version and exit.

       --show-datadir
              Print full path to GMT share directory and exit.

UNITS

       For map distance unit, append unit d for arc degree, m for arc minute, and s for arc  second,  or  e  for
       meter [Default], f for foot, k for km, M for statute mile, n for nautical mile, and u for US survey foot.
       By default we compute such distances using a spherical approximation with great circles. Prepend -  to  a
       distance  (or  the  unit  is no distance is given) to perform "Flat Earth" calculations (quicker but less
       accurate) or prepend + to perform exact geodesic calculations (slower but more accurate).

ASCII FORMAT PRECISION

       The ASCII output formats of numerical data are controlled by parameters in your gmt.conf file.  Longitude
       and  latitude  are formatted according to FORMAT_GEO_OUT, whereas other values are formatted according to
       FORMAT_FLOAT_OUT. Be aware that the format in effect can lead to loss of precision in the  output,  which
       can  lead  to  various  problems downstream. If you find the output is not written with enough precision,
       consider  switching  to  binary  output  (-bo  if  available)  or  specify  more   decimals   using   the
       FORMAT_FLOAT_OUT setting.

EXAMPLES

       To  combine  the digitized segment lines segment_*.txt (whose coordinates are in cm) into as few complete
       lines as possible, assuming the end points slop could be up to 0.1 mm, run

              gmt connect segment_*.txt -Tf0.1 > new_segments.txt

       To combine the digitized segments in  the  multisegment  file  my_lines.txt  (whose  coordinates  are  in
       lon,lat)  into  as few complete lines as possible, assuming the end points slop could be up to 150 m, and
       write the complete segments to separate files called  Map_segment_0001.dat,  Map_segment_0002.dat,  etc.,
       run

              gmt connect my_lines.txt -T150e -DMap_segment_%04d.dat

BUGS

       The  line connection does not work if a line only has a single point.  However, gmtconnect will correctly
       add the point to the nearest segment.  Running gmtconnect again on the new set of lines  will  eventually
       connect all close lines.

SEE ALSO

       gmt, gmt.conf, gmtsimplify, gmtspatial, mapproject

COPYRIGHT

       2015, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe