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.TH "GRDFILL" "1gmt" "Sep 07, 2019" "6.0.0rc4" "GMT"
.SH NAME
grdfill \- Interpolate across holes in a grid
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.SH SYNOPSIS
.sp
\fBgmt grdfill\fP \fIingrid\fP
 \fB\-A\fP\fImode\fP[\fIarg\fP]
 \fB\-G\fP\fIoutgrid\fP
[  \fB\-R\fP\fIregion\fP ]
[  \fB\-L\fP[\fBp\fP] ]
[  \fB\-V\fP[\fIlevel\fP] ]
[ \fB\-f\fPflags ]
[ \fB\-\-PAR\fP=\fIvalue\fP ]
.sp
\fBNote:\fP No space is allowed between the option flag and the associated arguments.
.SH DESCRIPTION
.sp
\fBgrdfill\fP reads a grid that presumably has unfilled holes that the user
wants to fill in some fashion.  Holes are identified by NaN values but
this criteria can be changed.  There are several different algorithms that
can be used to replace the hole values.
.SH REQUIRED ARGUMENTS
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.TP
.B \fIingrid\fP
This is the input grid file.
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.TP
\fB\-A\fP\fImode\fP[\fIarg\fP]
Specify the hole\-filling algorithm to use.  Choose from \fBc\fP for constant
fill and append the constant value, \fBn\fP for nearest neighbor and optionally
append a search radius in pixels, or \fBs\fP for bicubic spline [NOT IMPLEMENTED YET].
.UNINDENT
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.TP
\fB\-G\fP\fIoutgrid\fP
This is the output grid file.
.UNINDENT
.SH OPTIONAL ARGUMENTS
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.TP
\fB\-N\fP[\fInodata\fP]
Sets the node value that identifies a point as a member of a hole [Default is NaN].
.UNINDENT
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.TP
\fB\-R\fP\fIxmin\fP/\fIxmax\fP/\fIymin\fP/\fIymax\fP[\fB+r\fP][\fB+u\fP\fIunit\fP] (more ...)
Specify the region of interest. This defines the subregion to be cut out.
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.TP
\fB\-L\fP[\fBp\fP]
Just list the rectangular subregions west east south north of each hole.
No grid fill takes place and \fB\-G\fP is ignored. Optionally, append \fBp\fP
to instead write closed polygons for all subregions.
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.TP
\fB\-V\fP[\fIlevel\fP] (more ...)
Select verbosity level [c].  
.UNINDENT
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.TP
\fB\-f\fP[\fBi\fP|\fBo\fP]\fIcolinfo\fP (more ...)
Specify data types of input and/or output columns.  
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.TP
\fB\-^\fP or just \fB\-\fP
Print a short message about the syntax of the command, then exits (NOTE: on Windows just use \fB\-\fP).
.TP
\fB\-+\fP or just \fB+\fP
Print an extensive usage (help) message, including the explanation of
any module\-specific option (but not the GMT common options), then exits.
.TP
\fB\-?\fP or no arguments
Print a complete usage (help) message, including the explanation of all options, then exits.
.TP
\fB\-\-PAR\fP=\fIvalue\fP
Temporarily override a GMT default setting; repeatable. See /gmt.conf for parameters.
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.SH GEOGRAPHICAL AND TIME COORDINATES
.sp
When the output grid type is netCDF, the coordinates will be labeled
"longitude", "latitude", or "time" based on the attributes of the input
data or grid (if any) or on the \fB\-f\fP or \fB\-R\fP options. For example,
both \fB\-f0x\fP \fB\-f1t\fP and \fB\-R\fP90w/90e/0t/3t will result in a
longitude/time grid. When the x, y, or z coordinate is time, it will be
stored in the grid as relative time since epoch as specified by
TIME_UNIT and TIME_EPOCH in the
gmt.conf file or on the
command line. In addition, the \fBunit\fP attribute of the time variable
will indicate both this unit and epoch.
.SH EXAMPLES
.sp
To identify all regions with NaNs in the grid data.grd and create a listing of the
bounding coordinates of rectangular regions that would cover these NaN areas, try
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.sp
.nf
.ft C
gmt grdfill data.grd \-L > wesn_listing.txt
.ft P
.fi
.UNINDENT
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.sp
To identify the same areas but this time write a multisegment file with polygons
corresponding to the rectangular subregions, use
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.sp
.nf
.ft C
gmt grdfill data.grd \-Lp > NaN_regions.txt
.ft P
.fi
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.sp
To replace all NaN values in the file data.grd with the value 999.0, use
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.sp
.nf
.ft C
gmt grdfill data.grd \-Ac999 \-Gno_NaNs_data.grd
.ft P
.fi
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.sp
To replace all NaN values in the file data.grd with the values at the
nearest non\-NaN neighbor, try
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.sp
.nf
.ft C
gmt grdfill data.grd \-An \-Gno_NaNs_NN_data.grd
.ft P
.fi
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.SH SEE ALSO
.sp
gmt,
grdcut,
grdclip,
grdedit,
grdinfo
.SH COPYRIGHT
2019, The GMT Team
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