gdal_grid - Man Page

gdal_grid [--help] [--help-general]
          [-ot {Byte/Int16/UInt16/UInt32/Int32/Float32/Float64/
          CInt16/CInt32/CFloat32/CFloat64}]
          [-oo <NAME>=<VALUE>]...
          [-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>

This program creates a 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.

--help

Show this help message and exit

--help-general

Gives a brief usage message for the generic GDAL commandline options and exit.

-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, Int8, UInt16, Int16, UInt32, Int32, UInt64, Int64, Float32, Float64, CInt16, CInt32, CFloat32 or CFloat64.

If not set then a default type is used, which might not be supported by the relevant driver, causing a error.

-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 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 the Z value read from the feature geometry record (naturally, if you have a Z value in the geometry, otherwise you have no choice and should specify a field name containing a 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 the 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 the Z field. This can be used for a shift from e.g. feet to meters or from elevation to depth. The result value will be (Z value + Z increase value) * Z multiply value. The default value is 1.

-a {<algorithm>[[:<parameter1>=<value1>]...]}

Set the interpolation algorithm or data metric name and (optionally) its parameters. See the 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 with 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 an 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.

-oo <NAME>=<VALUE>

New in version 3.7.

Source dataset open option (format specific)

-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.

There are a number of interpolation algorithms to choose from.

More details about them can also be found in GDAL Grid Tutorial

Besides the interpolation functionality 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.
• radius: Set first and second radius (mutually exclusive with radius1 and radius2). Default is 0.0. Added in GDAL 3.6
• 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.
• max_points_per_quadrant: Maximum number of data points to use per quadrant. Default is 0. Added in GDAL 3.6. When specified, the algorithm will only take into account up to max_points_per_quadrant points for each of the right-top, left-top, right-bottom and right-top quadrant relative to the point being interpolated.
• min_points_per_quadrant: Minimum number of data points to use per quadrant. Default is 0. Added in GDAL 3.6. If that number is not reached, the point being interpolated will be set with the NODATA marker. When specified, the algorithm will collect at least min_points_per_quadrant points for each of the right-top, left-top, right-bottom and right-top quadrant relative to the point being interpolated.
• nodata: NODATA marker to fill empty points (default 0.0).

When min_points_per_quadrant or max_points_per_quadrant is specified, the search will start with the closest point to the point being interpolated from the first quadrant, then the closest point to the point being interpolated from the second quadrant, etc. up to the 4th quadrant, and will continue with the next closest point in the first quadrant, etc. until max_points and/or max_points_per_quadrant thresholds are reached.

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 gdal_grid. All you need is to create a virtual dataset header (VRT) for your CSV file and use it as an input datasource for gdal_grid. You can find details on the VRT format on the VRT -- Virtual Format description page.

Here is a small example. Let's say we have a CSV file called 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 the above data we will create a 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. The Z value will be used for interpolation. Now you can use dem.vrt with all OGR programs (start  with  ogrinfo  to  test  that everything works fine). The datasource will contain a single layer called "dem"  filled  with point features constructed from values in the CSV file. Using this technique you can handle CSV  files  with  more  than  three columns, switch columns, etc. OK, now the final step:

gdal_grid dem.vrt demv.tif

Or, if we do not wish to use a VRT file:

gdal_grid -l dem -oo X_POSSIBLE_NAMES=Easting \
-oo Y_POSSIBLE_NAMES=Northing -zfield Elevation dem.csv dem.tif

If your CSV file does not contain column headers then it can be handled in the VRT file 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.

Creating multiband files is not directly possible with gdal_grid. One might use gdal_grid multiple times to create one band per file, and then use gdalbuildvrt -separate and then gdal_translate:

gdal_grid ... 1.tif; gdal_grid ... 2.tif; gdal_grid ... 3.tif
gdalbuildvrt -separate 123.vrt 1.tif 2.tif 3.tif
gdal_translate 123.vrt 123.tif

Or just gdal_merge.py, to combine the one-band files into a single one:

gdal_grid ... a.tif; gdal_grid ... b.tif; gdal_grid ... c.tif
gdal_merge.py -separate a.tif b.tif c.tif -o d.tif

This utility is also callable from C with GDALGrid().

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 -zfield 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 "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

Andrey Kiselev <dron@ak4719.spb.edu>

1998-2024