SensorML Metadata specific to Optical Instruments (Sentinel 2)

Instrument Capabilities

Two new sections specific to optical instruments have to be added to the base sections common to all sentinels, defined in the common Instrument Capabilities documentation.

Examples below are extracted from the SPOT5 HRG Instrument description in SensorML.

Geometric Characteristics Section

This section lists all geometric characteristics applicable to an optical Instrument and plugs into the corresponding section of the Instrument Capabilities document.

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:GeometricCharacteristics">
   <swe:DataRecord>
      <gml:name>Geometric Characteristics</gml:name>
      <swe:field name="Across-Track FOV">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:AcrossTrackFov">
            <swe:uom code="deg"/>
            <swe:value>4.13</swe:value>
         </swe:Quantity>
      </swe:field>
      <swe:field name="Across-Track Pointing Range">
         <swe:QuantityRange definition="urn:ogc:def:property:CEOS:eop:AcrossTrackPointingRange">
            <swe:uom code="deg"/>
            <swe:value>-27 +27</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>60</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>50</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>3</swe:value>
         </swe:Quantity>
      </swe:field>               
   </swe:DataRecord>
</sml:characteristics>

Please take a look at the online dictionary to see a definition of these properties.

More Geometric Characteristics are defined for each Detector.

Measurement Characteristics Section

This section lists all measurement characteristics (related to radiometry) applicable to an optical 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="Number of Bands">
         <swe:Count definition="urn:ogc:def:property:CEOS:opt:NumberOfBands">
            <gml:description>Total number of bands for this instrument</gml:description>
            <swe:value>5</swe:value>
         </swe:Count>
      </swe:field>
   </swe:DataRecord>
</sml:characteristics>

More Measurement Characteristics are defined for each Detector.

Detector Section

As discussed in the inroduction, an optical Instrument is further divided into several Detector components which give the characteristics of each spectral band supported by the Instrument. This information should be included within the Detector component element that can be included inline or referenced in the Instrument Capabilities document's component section.

These examples are extracted from the SPOT-5 HRG HMA Detector.

Geometric Characteristics

This section is used to define each detector (i.e. band) geometric characteristics.

The following snippet shows the SensorML encoding of the mandatory characteristics in the Sentinel-2 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 Ground Resolution">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:AcrossTrackGroundResolution">
            <swe:uom code="m"/>
            <swe:value>5</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>5</swe:value>
         </swe:Quantity>
      </swe:field>
      <swe:field name="Number of Samples">
         <swe:Count definition="urn:ogc:def:property:CEOS:opt:NumberOfSamples">
            <swe:value>12000</swe:value>
         </swe:Count>
      </swe:field>
   </swe:DataRecord>
</sml:characteristics>

Optionally, iFOVs (i.e. instantaneous pixel FOV) can also specified:

<swe:field name="Across-Track iFOV">
    <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:AcrossTrackGroundIFOV">
         <swe:uom code="deg"/>
         <swe:value>3.3e-4</swe:value>
    </swe:Quantity>
</swe:field>

<swe:field name="Along-Track iFOV">
    <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:AlongTrackGroundIFOV">
         <swe:uom code="deg"/>
         <swe:value>3.3e-4</swe:value>
    </swe:Quantity>
</swe:field>

Measurement Characteristics

This section provides radiometric characteristics for each band.

<sml:characteristics xlink:role="urn:ogc:def:role:CEOS:eop:MeasurementCharacteristics">
   <swe:DataRecord>
      <gml:name>Measurement Characteristics</gml:name>
      <swe:field name="Band Type">
         <swe:Category definition="urn:ogc:def:property:CEOS:eop:BandType">
            <swe:codeSpace xlink:href="urn:ogc:def:dictionary:CEOS:eop:SpectralBands:v01"/>
            <swe:value>VIS</swe:value>
         </swe:Category>
      </swe:field>
      <swe:field name="Spectral Range">
         <swe:QuantityRange definition="urn:ogc:def:property:CEOS:opt:SpectralRange">
            <swe:uom code="nm"/>
            <swe:value>490 690</swe:value>
         </swe:QuantityRange>
      </swe:field>
      <swe:field name="SNR Ratio">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:SNR">
            <swe:uom code="dB"/>
            <swe:value>170</swe:value>
         </swe:Quantity>
      </swe:field>
      <swe:field name="Noise Equivalent Radiance">
         <swe:Quantity definition="urn:ogc:def:property:CEOS:eop:NEDR">
            <swe:uom code="W.m-2.sr.um-1"/>
            <swe:value>0.1</swe:value>
         </swe:Quantity>
      </swe:field>
   </swe:DataRecord>
</sml:characteristics>

The mandatory information is shown on the previous snippet, but as always more can easily be added.

Instrument Configurations

TBD

-- AlexandreRobin - 01 Feb 2008