Table of Contents
In this section, the EOxServer’s handling of raster file formats and OWS service specific format configuration is described.
The format registry is the list of raster file formats recognised by EOxServer. It holds definitions of both input and output formats. Each format record defines the MIME-type (unique, primary key), library, driver, and the default file extension.
Currently, EOxServer handles the raster data exclusively by means of the GDAL library. Thus, in principle, any raster file format supported by the GDAL library is supported by EOxServer. In particular, any raster file format readable by the GDAL library (provided that the file structure can be decomposed to one single-type, single- or multi-band image) can be used as the input and, vice versa, any raster file format writeable by the GDAL library can used as the output produced by WCS and WMS services.
Any raster file format intended to be used by EOxServer must be defined in the format registry. The format registry then provides unique mappings from MIME-type to the (GDAL) format driver.
The format registry configuration is split in two parts (files):
- per-installation (mandatory) format configuration (set up automatically during the EOxServer installation) defining the default baseline set of formats (
- per-instance (optional) format configuration allowing customization of the format registry (
In case of conflicting format definitions, the per-instance configuration takes precedence. Both formats’ configuration files share the same text file format.
The formats’ configuration is a simple text file containing a simple list of format definitions. One format definition (record) per line. Each record is then a comma separated list of the following text fields:
<MIME-type>, <driver>, <file extension>
The mime type is used as the primary key and thus any repeated MIME-type will
rewrite the previous format definition(s) using this MIME-type.
The driver field should be in format
GDAL/<GDAL driver name>. To list
available drivers provided by your GDAL installation use the following command:
- gdalinfo –formats
GDAL prefix is used as place-holder to allow future use of additional
library back-ends. The file extension shall be written including the separating
.. Any leading or trailing white-characters as well as empty lines
are ignored. The
# character is used as line-comment and any content
between this character and the end of the line is ignored.
An example format definition:
image/tiff,GDAL/GTiff,.tif # GeoTIFF raster file format
Since the list of supported drivers may vary for different installations of the back-end (GDAL) library, the library drivers are checked by EOxServer ignoring any format definitions requiring non-supported library drivers. Any invalid format record is reported to the EOxServer log. Further, EOxServer checks automatically which of the library drivers are ‘read-only’, i.e., which cannot be used to produce output images, and restricts these to be used for data input only.
The list of the file formats supported by the Web Coverage Service (WCS) is
specified in the EOxServer configuration (
path>/conf/eoxserver.conf) in the section
[services.ows.wcs] supported_formats=<MIME type>[,<MIME type>[,<MIME type> ... ]]
The supported WCS formats are specified as a comma-separated list of MIME-types. The listed MIME-types must be defined in the format registry otherwise they will be ignored. Read-only file formats will also be ignored.
The supported formats are announced through the WCS
CoverageDescription (the output may vary based on the WCS version used).
The use of in invalid MIME-types (not listed among the supported formats) in
getCoverge() requests will lead to errors (OWS Exceptions).
The native format (as defined by WCS 2.0.1 [OGC 09-110r4]) is the default
raster file format returned by the
getCoverage() operation in case of a
missing explicit format specification. By default, EOxServer sets the native
format to the format of the stored source data (source format), however, in
cases when the source format cannot be used (‘read-only’ source format) and/or
another default format is desired, EOxServer allows the configuration of
WCS native formats (
<instance path>/conf/eoxserver.conf, section
[services.ows.wcs20] default_native_format=<MIME-type> source_to_native_format_map=[<src.MIME-type,native-MIME-type>[,<src.MIME-type,native-MIME-type> ... ]]
The default native format option is used in cases when the source format cannot be used (read-only) and no source to native format mapping is present. This option must always be set to a valid format (GeoTIFF by default). The source to native format mapping, as the name suggests, maps the (zero, one, or more) source format(s) to non-default native formats. The source formats are not restricted to the read-only ones. This option accepts a comma-separated list of MIME-type pairs.
The list of the file formats supported by the Web Map Service’s (WMS)
getMap() operation is specified in the EOxServer configuration
<instance path>/conf/eoxserver.conf) in section
[services.ows.wms] supported_formats=<MIME type>[,<MIME type>[,<MIME type> ... ]]
The supported WMS formats are specified as a comma-separated list of MIME-types. The listed MIME-types must be defined in the format registry otherwise they will be ignored. The read-only file formats will be ignored.
The supported formats are announced through the WMS
output may vary based on the WMS version used).