Provided by: gdal-bin_3.5.1+dfsg-1build1_amd64 
NAME
gdal_grid - Creates regular grid from the scattered data.
SYNOPSIS
gdal_grid [-ot {Byte/Int16/UInt16/UInt32/Int32/Float32/Float64/
CInt16/CInt32/CFloat32/CFloat64}]
[-of format] [-co "NAME=VALUE"]
[-zfield field_name] [-z_increase increase_value] [-z_multiply multiply_value]
[-a_srs srs_def] [-spat xmin ymin xmax ymax]
[-clipsrc <xmin ymin xmax ymax>|WKT|datasource|spat_extent]
[-clipsrcsql sql_statement] [-clipsrclayer layer]
[-clipsrcwhere expression]
[-l layername]* [-where expression] [-sql select_statement]
[-txe xmin xmax] [-tye ymin ymax] [-tr xres yres] [-outsize xsize ysize]
[-a algorithm[:parameter1=value1]*] [-q]
<src_datasource> <dst_filename>
DESCRIPTION
This program creates regular grid (raster) from the scattered data read from the OGR
datasource. Input data will be interpolated to fill grid nodes with values, you can choose
from various interpolation methods.
It is possible to set the GDAL_NUM_THREADS configuration option to parallelize the
processing. The value to specify is the number of worker threads, or ALL_CPUS to use all
the cores/CPUs of the computer.
-ot <type>
Force the output image bands to have a specific data type supported by the driver,
which may be one of the following: Byte, UInt16, Int16, UInt32, Int32, Float32,
Float64, CInt16, CInt32, CFloat32 or CFloat64.
-of <format>
Select the output format. Starting with GDAL 2.3, if not specified, the format is
guessed from the extension (previously was GTiff). Use the short format name.
-txe <xmin> <xmax>
Set georeferenced X extents of output file to be created.
-tye <ymin> <ymax>
Set georeferenced Y extents of output file to be created.
-tr <xres> <yres>
Set output file resolution (in target georeferenced units). Note that -tr just
works in combination with a valid input from -txe and -tye
New in version 3.2.
-outsize <xsize ysize>
Set the size of the output file in pixels and lines. Note that -outsize cannot be
used with -tr
-a_srs <srs_def>
Override the projection for the output file. The <i>srs_def> may be any of the
usual GDAL/OGR forms, complete WKT, PROJ.4, EPSG:n or a file containing the WKT.
No reprojection is done.
-zfield <field_name>
Identifies an attribute field on the features to be used to get a Z value from.
This value overrides Z value read from feature geometry record (naturally, if you
have a Z value in geometry, otherwise you have no choice and should specify a field
name containing Z value).
-z_increase <increase_value>
Addition to the attribute field on the features to be used to get a Z value from.
The addition should be the same unit as Z value. The result value will be Z value +
Z increase value. The default value is 0.
-z_multiply <multiply_value>
This is multiplication ratio for Z field. This can be used for shift from e.g. foot
to meters or from elevation to deep. The result value will be (Z value + Z increase
value) * Z multiply value. The default value is 1.
-a <[algorithm[:parameter1=value1][:parameter2=value2]...]>
Set the interpolation algorithm or data metric name and (optionally) its
parameters. See Interpolation algorithms and Data metrics sections for further
discussion of available options.
-spat <xmin> <ymin> <xmax> <ymax>
Adds a spatial filter to select only features contained within the bounding box
described by (xmin, ymin) - (xmax, ymax).
-clipsrc [xmin ymin xmax ymax]|WKT|datasource|spat_extent
Adds a spatial filter to select only features contained within the specified
bounding box (expressed in source SRS), WKT geometry (POLYGON or MULTIPOLYGON),
from a datasource or to the spatial extent of the -spat option if you use the
spat_extent keyword. When specifying a datasource, you will generally want to use
it in combination of the -clipsrclayer, -clipsrcwhere or -clipsrcsql options.
-clipsrcsql <sql_statement>
Select desired geometries using an SQL query instead.
-clipsrclayer <layername>
Select the named layer from the source clip datasource.
-clipsrcwhere <expression>
Restrict desired geometries based on attribute query.
-l <layername>
Indicates the layer(s) from the datasource that will be used for input features.
May be specified multiple times, but at least one layer name or a -sql option must
be specified.
-where <expression>
An optional SQL WHERE style query expression to be applied to select features to
process from the input layer(s).
-sql <select_statement>
An SQL statement to be evaluated against the datasource to produce a virtual layer
of features to be processed.
-co <NAME=VALUE>
Many formats have one or more optional creation options that can be used to control
particulars about the file created. For instance, the GeoTIFF driver supports
creation options to control compression, and whether the file should be tiled.
The creation options available vary by format driver, and some simple formats have
no creation options at all. A list of options supported for a format can be listed
with the --formats command line option but the documentation for the format is the
definitive source of information on driver creation options. See Raster drivers
format specific documentation for legal creation options for each format.
-q Suppress progress monitor and other non-error output.
<src_datasource>
Any OGR supported readable datasource.
<dst_filename>
The GDAL supported output file.
INTERPOLATION ALGORITHMS
There are number of interpolation algorithms to choose from.
More details about them can also be found in GDAL Grid Tutorial
invdist
Inverse distance to a power. This is default algorithm. It has following parameters:
• power: Weighting power (default 2.0).
• smoothing: Smoothing parameter (default 0.0).
• radius1: The first radius (X axis if rotation angle is 0) of search ellipse. Set this
parameter to zero to use whole point array. Default is 0.0.
• radius2: The second radius (Y axis if rotation angle is 0) of search ellipse. Set this
parameter to zero to use whole point array. Default is 0.0.
• angle: Angle of search ellipse rotation in degrees (counter clockwise, default 0.0).
• max_points: Maximum number of data points to use. Do not search for more points than
this number. This is only used if search ellipse is set (both radii are non-zero). Zero
means that all found points should be used. Default is 0.
• min_points: Minimum number of data points to use. If less amount of points found the
grid node considered empty and will be filled with NODATA marker. This is only used if
search ellipse is set (both radii are non-zero). Default is 0.
• nodata: NODATA marker to fill empty points (default 0.0).
invdistnn
New in version 2.1.
Inverse distance to a power with nearest neighbor searching, ideal when max_points is
used. It has following parameters:
• power: Weighting power (default 2.0).
• smoothing: Smoothing parameter (default 0.0).
• radius: The radius of the search circle, which should be non-zero. Default is 1.0.
• max_points: Maximum number of data points to use. Do not search for more points than
this number. Found points will be ranked from nearest to furthest distance when
weighting. Default is 12.
• min_points: Minimum number of data points to use. If less amount of points found the
grid node is considered empty and will be filled with NODATA marker. Default is 0.
• nodata: NODATA marker to fill empty points (default 0.0).
average
Moving average algorithm. It has following parameters:
• radius1: The first radius (X axis if rotation angle is 0) of search ellipse. Set this
parameter to zero to use whole point array. Default is 0.0.
• radius2: The second radius (Y axis if rotation angle is 0) of search ellipse. Set this
parameter to zero to use whole point array. Default is 0.0.
• angle: Angle of search ellipse rotation in degrees (counter clockwise, default 0.0).
• min_points: Minimum number of data points to use. If less amount of points found the
grid node considered empty and will be filled with NODATA marker. Default is 0.
• nodata: NODATA marker to fill empty points (default 0.0).
Note, that it is essential to set search ellipse for moving average method. It is a window
that will be averaged when computing grid nodes values.
nearest
Nearest neighbor algorithm. It has following parameters:
• radius1: The first radius (X axis if rotation angle is 0) of search ellipse. Set this
parameter to zero to use whole point array. Default is 0.0.
• radius2: The second radius (Y axis if rotation angle is 0) of search ellipse. Set this
parameter to zero to use whole point array. Default is 0.0.
• angle: Angle of search ellipse rotation in degrees (counter clockwise, default 0.0).
• nodata: NODATA marker to fill empty points (default 0.0).
linear
New in version 2.1.
Linear interpolation algorithm.
The Linear method performs linear interpolation by computing a Delaunay triangulation of
the point cloud, finding in which triangle of the triangulation the point is, and by doing
linear interpolation from its barycentric coordinates within the triangle. If the point
is not in any triangle, depending on the radius, the algorithm will use the value of the
nearest point or the nodata value.
It has following parameters:
• radius: In case the point to be interpolated does not fit into a triangle of the
Delaunay triangulation, use that maximum distance to search a nearest neighbour, or use
nodata otherwise. If set to -1, the search distance is infinite. If set to 0, nodata
value will be always used. Default is -1.
• nodata: NODATA marker to fill empty points (default 0.0).
DATA METRICS
Besides the interpolation functionality ref gdal_grid can be used to compute some data
metrics using the specified window and output grid geometry. These metrics are:
• minimum: Minimum value found in grid node search ellipse.
• maximum: Maximum value found in grid node search ellipse.
• range: A difference between the minimum and maximum values found in grid node search
ellipse.
• count: A number of data points found in grid node search ellipse.
• average_distance: An average distance between the grid node (center of the search
ellipse) and all of the data points found in grid node search ellipse.
• average_distance_pts: An average distance between the data points found in grid node
search ellipse. The distance between each pair of points within ellipse is calculated
and average of all distances is set as a grid node value.
All the metrics have the same set of options:
• radius1: The first radius (X axis if rotation angle is 0) of search ellipse. Set this
parameter to zero to use whole point array. Default is 0.0.
• radius2: The second radius (Y axis if rotation angle is 0) of search ellipse. Set this
parameter to zero to use whole point array. Default is 0.0.
• angle: Angle of search ellipse rotation in degrees (counter clockwise, default 0.0).
• min_points: Minimum number of data points to use. If less amount of points found the
grid node considered empty and will be filled with NODATA marker. This is only used if
search ellipse is set (both radii are non-zero). Default is 0.
• nodata: NODATA marker to fill empty points (default 0.0).
READING COMMA SEPARATED VALUES
Often you have a text file with a list of comma separated XYZ values to work with (so
called CSV file). You can easily use that kind of data source in ref gdal_grid. All you
need is create a virtual dataset header (VRT) for you CSV file and use it as input
datasource for ref gdal_grid. You can find details on VRT format at VRT -- Virtual Format
description page.
Here is a small example. Let we have a CSV file called <i>dem.csv> containing
Easting,Northing,Elevation
86943.4,891957,139.13
87124.3,892075,135.01
86962.4,892321,182.04
87077.6,891995,135.01
...
For above data we will create <i>dem.vrt> header with the following content:
<OGRVRTDataSource>
<OGRVRTLayer name="dem">
<SrcDataSource>dem.csv</SrcDataSource>
<GeometryType>wkbPoint</GeometryType>
<GeometryField encoding="PointFromColumns" x="Easting" y="Northing" z="Elevation"/>
</OGRVRTLayer>
</OGRVRTDataSource>
This description specifies so called 2.5D geometry with three coordinates X, Y and Z. Z
value will be used for interpolation. Now you can use <i>dem.vrt> with all OGR programs
(start with ref ogrinfo to test that everything works fine). The datasource will contain
single layer called <i>"dem"> filled with point features constructed from values in CSV
file. Using this technique you can handle CSV files with more than three columns, switch
columns, etc.
If your CSV file does not contain column headers then it can be handled in the following
way:
<GeometryField encoding="PointFromColumns" x="field_1" y="field_2" z="field_3"/>
The Comma Separated Value (.csv) description page contains details on CSV format supported
by GDAL/OGR.
C API
This utility is also callable from C with GDALGrid().
EXAMPLES
The following would create raster TIFF file from VRT datasource described in Reading comma
separated values section using the inverse distance to a power method. Values to
interpolate will be read from Z value of geometry record.
gdal_grid -a invdist:power=2.0:smoothing=1.0 -txe 85000 89000 -tye 894000 890000 -outsize 400 400 -of GTiff -ot Float64 -l dem dem.vrt dem.tiff
The next command does the same thing as the previous one, but reads values to interpolate
from the attribute field specified with <b>-zfield</b> option instead of geometry record.
So in this case X and Y coordinates are being taken from geometry and Z is being taken
from the <i>"Elevation"> field. The GDAL_NUM_THREADS is also set to parallelize the
computation.
gdal_grid -zfield "Elevation" -a invdist:power=2.0:smoothing=1.0 -txe 85000 89000 -tye 894000 890000 -outsize 400 400 -of GTiff -ot Float64 -l dem dem.vrt dem.tiff --config GDAL_NUM_THREADS ALL_CPUS
AUTHOR
Andrey Kiselev <dron@ak4719.spb.edu>
COPYRIGHT
1998-2022
Jun 30, 2022 GDAL_GRID(1)