MB-System Unix Manual Page: mbm_grdcut

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    mbm_grdcut
    Section:  MB-System 5.0  (1)
    Updated:  26 October 2009
    Index

    NAME

    mbm_grdcut - Macro to extract a specified subarea of a
    GMT GRD grid file as another GRD file.

    VERSION

    Version 5.0

    SYNOPSIS

    mbm_grdcut -Iinfile -Ooutfile -Rw/e/s/n [-H -V]

    DESCRIPTION

    mbm_grdcut is a macro to painlessly cut out a region from a
    GMT GRD grid file.
    The GMT program grdcut requires that one specify bounds which
    exactly match grid cell boundaries. Frequently, one just wants
    to extract an approximate region quickly, without calculating
    grid cell sizes and boundary locations. This macro does the
    the calculations and extracts the subregion closest to that
    specified by the user.

    AUTHORSHIP

    David W. Caress (caress@mbari.org)

      Monterey Bay Aquarium Research Institute

    Dale N. Chayes (dale@ldeo.columbia.edu)

      Lamont-Doherty Earth Observatory

    OPTIONS

    -H

    This "help" flag cause the program to print out a description
    of its operation and then exit immediately.
    -I

    infile

    Sets the filename of the input GMT grid file. This file must be
    in the GMT NetCDF GRD format.
    -O

    outfile

    Sets the filename of the output GMT grid file. This file will be
    in the GMT NetCDF GRD format.
    -R

    w/e/s/n

    Sets the bounds of the area to be extracted from the input grid file.
    -V

    The -V option causes mbm_grdcut to print out status messages.

    EXAMPLES

    Suppose that we have used mbgrid to obtain a
    topography grid file called KohalaA_bath.grd in the GMT NetCDF
    GRD format:

            mbgrid -Idatalist \

                    -OKohalaA_bath \

                    -R-155.72855/-155.31928/20.09488/20.47645 \

                    -E30.0/0m! -A2 -N -G3 -C1 -V

    Further suppose that one wishes to extract a smaller grid with
    bounds of 155 degrees 31 minutes W to 155 degrees 26 minutes W
    in longitude and 20 degrees 13 minutes N to 20 degrees 18 minutes N
    in latitude. This can be done using the GMT program
    grdcut, but grdcut requires that the user specify
    bounds that exactly match the grid cell boundaries in the file.
    The mbm_grdcut macros allows one to specify approximate
    desired bounds, calculates the exact, nearest bounds
    that grdcut will accept, and then executes grdcut.

    To obtain the desired sub-grid, the following will suffice:

            mbm_grdcut -I KohalaA_bath.grd                  -O Kohala_plunge                -R-155:31/-155:26/20:13/20:18 -V

    The resulting output is:

            Program mbm_grdcut status:

                    Input GRD file:         kohalaa.grd

                    Output GRD file:        z.grd

                    Input Grid bounds:      -155.72855 -155.3192906  20.09488 20.47628103

                    Input grid dimensions:  1426  1329

                    Grid cell sizes:        0.0002871995719  0.0002871995719

                    Requested Grid bounds:  -155.516666666667 -155.433333333333  20.2166666666667 20.3

                    Output Grid bounds:     -155.51688391551 -155.433596039659  20.2166526184856 20.2999404943366

                    Output grid dimensions: 291  291

            Running grdcut...

            grdcut kohalaa.grd -Gz.grd -R-155.51688391551/-155.433596039659/20.2166526184856/20.2999404943366 -V

            grdcut: File spec:      W E S N dx dy nx ny:

            grdcut: Old: -155.729 -155.319 20.0949 20.4763 0.0002872 0.0002872 1426 1329

            grdcut: New: -155.517 -155.434 20.2167 20.2999 0.0002872 0.0002872  291  291

    SEE ALSO

    mbsystem(l), mbgrid(l),
    mbmosaic(l), mbm_grid(l), mbm_grdplot(l)

    BUGS

    This macro is new and hasn't been tested in serious
    usage yet - let us know what to fix, add, or
    change!.

     Index

    NAME
    VERSION
    SYNOPSIS
    DESCRIPTION
    AUTHORSHIP
    OPTIONS
    EXAMPLES
    SEE ALSO
    BUGS

Last Updated: 26 October 2009

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