creates regular grid from the scattered data
Usage: gdal_grid [--help-general] [--formats]
[-ot {Byte/Int16/UInt16/UInt32/Int32/Float32/Float64/
CInt16/CInt32/CFloat32/CFloat64}]
[-of format] [-co "NAME=VALUE"]
[-zfield field_name]
[-a_srs srs_def] [-spat xmin ymin xmax ymax]
[-l layername]* [-where expression] [-sql select_statement]
[-txe xmin xmax] [-tye ymin ymax] [-outsize xsize ysize]
[-a algorithm[:parameter1=value1]*] [-quiet]
<src_datasource> <dst_filename>
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.
For the output bands to be of the indicated data type.
Select the output format. The default is GeoTIFF (GTiff). Use the short format name.
Set georeferenced X extents of output file to be created.
Set georeferenced Y extents of output file to be created.
Set the size of the output file in pixels and lines.
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.
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).
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.
Adds a spatial filter to select only features intersecting the bounding box described by (xmin, ymin) - (xmax, ymax).
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.
An optional SQL WHERE style query expression to be applied to select features to process from the input layer(s).
An SQL statement to be evaluated against the datasource to produce a virtual layer of features to be processed.
Passes a creation option to the output format driver. Multiple -co options may be listed. See format specific documentation for legal creation options for each format.
Suppress progress monitor and other non-error output.
Any OGR supported readable datasource.
The GDAL supported output file.
There are number of interpolation algorithms to choose from.
Inverse distance to a power. This is default algorithm. It has following parameters:
Moving average algorithm. It has following parameters:
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 neighbor algorithm. It has following parameters:
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 value found in grid node search ellipse.
Maximum value found in grid node search ellipse.
A difference between the minimum and maximum values found in grid node search ellipse.
All the metrics have the same set of options:
NODATA marker to fill empty points (default 0.0).
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 create a virtual dataset header (VRT) for you CSV file and use it as input datasource for gdal_grid. You can find details on VRT format at Virtual Format description page.
Here is a small example. Let 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 above data we will create 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 dem.vrt with all OGR programs (start with ogrinfo to test that everything works fine). The datasource will contain single layer called "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"/>
Comma Separated Value description page contains details on CSV format supported by GDAL/OGR.
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 previos 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.
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
1.6.2-20100208.