SensorML Metadata specific to SAR Instruments (Sentinel 1)

Instrument Capabilities

Two new sections specific to SAR Instrumentsi have to be added to the base sections common to all sentinels and defined in the common _Instrument Capabilities documentation.

Examples in this section are extracted from the ENVISAT ASAR instrument description.

Capabilities - Geometric Characteristics Section

This section lists all geometric characteristics applicable to a SAR Instrument. The following snippet shows the set of mandatory characteristics required by the sentinel 1 profile:

<sml:characteristics xlink:role="urn:ogc:def:role:CEOS:eop:GeometricCharacteristics">
   <swe:DataRecord>
      <gml:name>Geometric Characteristics</gml:name>
      <swe:field name="Antenna Length">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:sar:AntennaLength">
            <swe:uom code="m"/>
            <swe:value>10</swe:value>
         </swe:Quantity>
      </swe:field>
      <swe:field name="Antenna Width">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:sar:AntennaWidth">
            <swe:uom code="m"/>
            <swe:value>1.3</swe:value>
         </swe:Quantity>
      </swe:field>
      <swe:field name="Ground Location Accuracy">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:GroundLocationAccuracy">
            <swe:uom code="m"/>
            <swe:value>000</swe:value>
         </swe:Quantity>
      </swe:field>
      <swe:field name="Revisit Time">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:RevisitTime">
            <swe:uom code="d"/>
            <swe:value>000</swe:value>
         </swe:Quantity>
      </swe:field>
   </swe:DataRecord>
</sml:characteristics>

Capabilities - Measurement Characteristics Section

This section lists all radiometric characteristics applicable to a SAR Instrument. The following snippet shows the set of mandatory characteristics required by the sentinel 2 profile:

<sml:characteristics xlink:role="urn:ogc:def:role:CEOS:eop:MeasurementCharacteristics">
   <swe:DataRecord>
      <gml:name>Measurement Characteristics</gml:name>
      <swe:field name="Transmit Frequency Band">
         <swe:Category definition="urn:ogc:def:property:CEOS:sar:TransmitFrequencyBand">
            <swe:codeSpace xlink:href="urn:ogc:def:dictionary:CEOS:eop:SpectralBands:v01"/>
            <swe:value>C</swe:value>
         </swe:Category>
      </swe:field>
      <swe:field name="Transmit Center Frequency">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:sar:TransmitCenterFrequency">
            <swe:uom code="GHz"/>
            <swe:value>5.331</swe:value>
         </swe:Quantity>
      </swe:field>                      
   </swe:DataRecord>
</sml:characteristics>

Capabilities - Detector Section

There is no detector section in a SAR instrument. However, most SAR instruments have multiple modes with different geometric and radiometric characteristics. It is thus necessary to describe each mode in a separate document as documented in the following section.

Instrument Configurations

Most detailed characteristics depend on the mode of operation in a SAR Instrument, thus a lot of geometric and radiometric characteristics are defined (or redefined) at the Instrument Configuration level, as documented in this section.

Examples in this section are extracted from the ENVISAT ASAR ImageMode document.

Configuration - Geometric Characteristics Section

Below is the list of mandatory characteristics that should be provided when following the GMES PH SAR profile:

<sml:characteristics xlink:role="urn:ogc:def:role:CEOS:eop:GeometricCharacteristics">
   <swe:DataRecord>
      <gml:name>Geometric Characteristics</gml:name>
      <swe:field name="Across-Track Pointing Range">
         <swe:QuantityRange definition="urn:ogc:def:property:CEOS:eop:AcrossTrackPointingRange">
            <swe:uom code="deg"/>
            <swe:value>15 45</swe:value>
         </swe:QuantityRange>
      </swe:field>
      <swe:field name="Along-Track Pointing Range">
         <swe:QuantityRange definition="urn:ogc:def:property:CEOS:eop:AlongTrackPointingRange">
            <swe:uom code="deg"/>
            <swe:value>-0 +0</swe:value>
         </swe:QuantityRange>
      </swe:field>               
      <swe:field name="Swath Width">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:NadirSwathWidth">
            <swe:uom code="km"/>
            <swe:value>100</swe:value>
         </swe:Quantity>
      </swe:field>
      <swe:field name="Across-Track Ground Resolution">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:AcrossTrackGroundResolution">
            <swe:uom code="m"/>
            <swe:value>28</swe:value>
         </swe:Quantity>
      </swe:field>
      <swe:field name="Along-Track Ground Resolution">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:AlongTrackGroundResolution">
            <swe:uom code="m"/>
            <swe:value>28</swe:value>
         </swe:Quantity>
      </swe:field>
   </swe:DataRecord>
</sml:characteristics>

Configuration - Measurement Characteristics

This section includes the list of all mode specific radiometric characteristics.

<sml:characteristics xlink:role="urn:ogc:def:role:CEOS:eop:MeasurementCharacteristics">
   <swe:DataRecord>
      <gml:name>Measurement Characteristics</gml:name>
      <swe:field name="Radiometric Resolution">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:RadiometricResolution">
            <swe:uom code="dB"/>
            <swe:value>1.5</swe:value>
         </swe:Quantity>
      </swe:field>
      <swe:field name="Radiometric Stability">
         <swe:QuantityRange definition="urn:ogc:def:property:CEOS:sar:RadiometricStability">
            <swe:uom code="dB"/>
            <swe:value>0.32 0.40</swe:value>
         </swe:QuantityRange>
      </swe:field>
      <swe:field name="Along-Track Ambiguity Ratio">
         <swe:QuantityRange definition="urn:ogc:def:property:CEOS:sar:AlongTrackAmbiguityRatio">
            <swe:uom code="dB"/>
            <swe:value>26 30</swe:value>
         </swe:QuantityRange>
      </swe:field>
      <swe:field name="Across-Track Ambiguity Ratio">
         <swe:QuantityRange definition="urn:ogc:def:property:CEOS:sar:AcrossTrackAmbiguityRatio">
            <swe:uom code="dB"/>
            <swe:value>32 46</swe:value>
         </swe:QuantityRange>
      </swe:field>
      <swe:field name="Noise Equivalent S0">
         <swe:QuantityRange definition="urn:ogc:def:property:CEOS:sar:NoiseEquivalentS0">
            <swe:uom code="dB"/>
            <swe:value>-22 -22</swe:value>
         </swe:QuantityRange>
      </swe:field>
      <swe:field name="Polarization">
         <swe:Category definition="urn:ogc:def:property:CEOS:sar:PolarizationMode">
            <swe:codeSpace xlink:href="urn:ogc:def:dictionary:CEOS:sar:PolarizationTypes:v01"/>
            <swe:value>HH</swe:value>
         </swe:Category>
      </swe:field>
      <swe:field name="Polarization">
         <swe:Category definition="urn:ogc:def:property:CEOS:sar:PolarizationMode">
            <swe:codeSpace xlink:href="urn:ogc:def:dictionary:CEOS:sar:PolarizationTypes:v01"/>
            <swe:value>VV</swe:value>
         </swe:Category>
      </swe:field>    
   </swe:DataRecord>
</sml:characteristics>

As can be seen on this example, one or more Polarization parameter can be included in order to list all possible polarization modes in this configuration.

-- AlexandreRobin - 01 Feb 2008