MERIS Level 1 Radiometric Processor - Command Line Description |

### Processor Description

Since the MERIS Radiometric Correction processor makes use of the SNAP graph processing framework, it can be used also as a command line tool. The graph processing is invoked by the command

- ${OPTTBX-INSTALL-DIR}/bin/gpt

To obtain general help on the graph processing, use the command

- ${OPTTBX-INSTALL-DIR}/bin/gpt -h

Specific help on the MERIS Radiometry Correction processor, can be obtained with

- ${OPTTBX-INSTALL-DIR}/bin/gpt -h Meris.CorrectRadiometry

In this case, information on the usage and a list of all available parameters are given.

If MERIS N1 products shall be written as output result a graph xml file has to be created. This xml file should concatenate the Meris.CorrectRadiometry operator and the Meris.N1Patcher operator. A possible graph xml file would look like the following. For demonstration purpose only the necessary parameter have been set.

        <graph id="RadiometryCorrectionN1">
            <version>1.0</version>
            <node id="radiometry">
                <operator>Meris.CorrectRadiometry</operator>
                <sources>
                    <source>${n1Product}</source>
                </sources>

            </node>
            <node id="n1Writer">
                <operator>Meris.N1Patcher</operator>
                <sources>
                    <n1>${n1Product}</n1>
                    <input>radiometry</input>
                </sources>
                <parameters>
                    <patchedFile>${n1TargetFile}</patchedFile>
                </parameters>
            </node>
        </graph>

This graph can be invoked by the following call on the command line:

      gpt <graph-file.xml> -Pn1TargetFile=<path-to-target-file> -Sn1Product=<path-to-source-file>