.TH GRDINFO 1gmt "Feb 27 2014" "GMT 4.5.13 (SVN)" "Generic Mapping Tools"
.SH NAME
grdinfo \- Get information about the contents of a 2-D grid file
.SH SYNOPSIS
\fBgrdinfo\fP \fIgrdfiles\fP [ \fB\-C\fP ] [ \fB\-F\fP ] 
[ \fB\-I\fP[\fIdx\fP[/\fIdy\fP]] ][ \fB\-L\fP[\fB0\fP|\fB1\fP|\fP2\fP] ] 
[ \fB\-M\fP ] [ \fB\-T\fP\fIdz\fP ] [ \fB\-V\fP ] [ \fB\-f\fP[\fBi\fP|\fBo\fP]\fIcolinfo\fP ]
.SH DESCRIPTION
\fBgrdinfo\fP reads a 2-D binary grid file and reports various statistics for
the (\fIx,y,z\fP) data in the grid file(s).  The output information contains the
minimum/maximum values for \fIx\fP, \fIy\fP, and \fIz\fP, where the min/max of \fIz\fP occur, the
\fIx\fP- and \fIy\fP-increments, and the number of \fIx\fP and \fIy\fP nodes, and [optionally] the
mean, standard deviation, and/or the median, L1 scale of \fIz\fP, and number of
nodes set to NaN.
.TP
\fIgrdfile\fP
The name of one or several 2-D grid files.
(See GRID FILE FORMATS below.)
.SH OPTIONS
No space between the option flag and the associated arguments.
.TP
\fB\-C\fP
Formats the report using tab-separated fields on a single line.  The output is
\fIw e s n z0 z1 dx dy nx ny \fP[ \fIx0 y0 x1 y1\fP ] [ \fImed scale\fP ] [\fI mean std rms\fP] [\fIn_nan\fP].
The data in brackets are output only if the corresponding options
\fB\-M\fP, \fB\-L1\fP, \fB\-L2\fP, and \fB\-M\fP are used, respectively.
If the \fB\-I\fP option is used, the output format is instead
\fINF w e s n z0 z1\fP, where \fINF\fP is the total number of grids read and \fIw e s n\fP are rounded off (see \fB\-I\fP).
.TP
\fB\-F\fP
Report grid domain and x/y-increments in world mapping format [Default is generic].
Does not apply to the \fB\-C\fP option.
.TP
\fB\-I\fP
Report the min/max of the region to the nearest multiple of \fIdx\fP and \fIdy\fP,
and output this in the form \fB\-R\fP\fIw/e/s/n\fP (unless \fB\-C\fP is set).
To report the actual grid region, select \fB\-I-\fP.  If no argument is given
then we report the grid increment in the form \fB\-I\fP\fIxinc/yinc\fP.
.TP
\fB\-L0\fP
Report range of z after actually scanning the data, not just reporting what the header says.
.TP
\fB\-L1\fP
Report median and L1 scale of z (L1 scale = 1.4826 * Median Absolute Deviation (MAD)).
.TP
\fB\-L2\fP
Report mean, standard deviation, and rms of z.
.TP
\fB\-M\fP
Find and report the location of min/max z-values, and count and report the number of nodes
set to NaN, if any.
.TP
\fB\-T\fP
Determine min and max z-value, round off to multiples of \fIdz\fP, and report as the text string
\fB\-T\fP\fIzmin/zmax/dz\fP for use by \fBmakecpt\fP.
.TP
\fB\-V\fP
Selects verbose mode, which will send progress reports to stderr [Default runs "silently"].
.TP
\fB\-f\fP
Special formatting of input and/or output columns (time or geographical data).
Specify \fBi\fP or \fBo\fP to make this apply only to input or output [Default applies to both].
Give one or more columns (or column ranges) separated by commas.
Append \fBT\fP (absolute calendar time), \fBt\fP (relative time in chosen \fBTIME_UNIT\fP since \fBTIME_EPOCH\fP),
\fBx\fP (longitude), \fBy\fP (latitude), or \fBf\fP (floating point) to each column
or column range item.  Shorthand \fB\-f\fP[\fBi\fP|\fBo\fP]\fBg\fP means \fB\-f\fP[\fBi\fP|\fBo\fP]0\fBx\fP,1\fBy\fP
(geographic coordinates).
.SH GRID FILE FORMATS
\fBGMT\fP is able to recognize many of the commonly used grid file formats, as well as the precision, scale and offset of the values
contained in the grid file. When \fBGMT\fP needs a little help with that, you can add the suffix \fB=\fP\fIid\fP[\fB/\fP\fIscale\fP\fB/\fP\fIoffset\fP[\fB/\fP\fInan\fP]],
where \fIid\fP is a two-letter identifier of the grid type and precision, and \fIscale\fP and \fIoffset\fP are optional scale factor
and offset to be applied to all grid values, and \fInan\fP is the value used to indicate missing data.
See \fBgrdreformat\fP(1) and Section 4.17 of the GMT Technical Reference and Cookbook for more information.
.P
When reading a netCDF file that contains multiple grids, \fBGMT\fP will read, by default, the first 2-dimensional grid that can find in that
file. To coax \fBGMT\fP into reading another multi-dimensional variable in the grid file, append \fB?\fP\fIvarname\fP to the file name, where
\fIvarname\fP is the name of the variable. Note that you may need to escape the special meaning of \fB?\fP in your shell program
by putting a backslash in front of it, or by placing the filename and suffix between quotes or double quotes.
See \fBgrdreformat\fP(1) and Section 4.18 of the GMT Technical Reference and Cookbook for more information,
particularly on how to read splices of 3-, 4-, or 5-dimensional grids.
.SH EXAMPLES
To obtain all the information about the data set in file hawaii_topo.grd:
.br
.sp
\fBgrdinfo\fP \fB\-L1\fP \fB\-L2\fP \fB\-M\fP hawaii_topo.grd
.SH "SEE ALSO"
.IR GMT (1),
.IR grd2cpt (1),
.IR grd2xyz (1),
.IR grdedit (1)