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Applicability of WIGOS for EUMETSAT Satellite Earth Observations
TT-WMD-5 (DEC 2016) Guillaume Aubert
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Introduction Background:
Assess usage of WIGOS Metadata Standard for EUMETSAT Satellite observations Target: Evaluate if the WIGOS standard (abstract model) is suitable (or not) to describe EO data from EUM Meteorological Satellites. Assumptions: Lots of the WIGOS elements are not relevant for EO but much more related to in-situ sensors. Some elements may be missing which are evident for describing EO related datasets.
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Introduction Objectives:
Define compulsory metadata elements related to earth observation data that are not yet covered by WIGOS Metadata Provide information on what should be changed / added to allow a correct description of EO data based on satellite observations
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Experience with metadata for Earth Observation
EUMETSAT involved in interoperability projects for more than 10 years Earth Observation Product Metadata definition Participation to ESA Heterogeneous Missions Access (HMA) project Definition of an information model based on ISO and OGC O&M (OGC r40) profile called HMA O&M EOP Use of metadata for the EUMETSAT Archive in the Submission Information Package (SIP) SIP based on O&M EOP Extensive metadata description for each measurements (every 3 min) Compare WIGOS against HMA EO Metadata Similar level of information Contain minimum level of information to describe EO data
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Background: Collection and Product Metadata
In HMA EO, metadata was organised with a two-step approach: EO collections defined as sets of EO products sharing common generic characteristics e.g. products of the same satellite (e.g. MSG) and the same instrument sensor (e.g. SEVIRI) acquired at different times. Collection metadata elements:, data access, access constraints, producer, acquisition type (e.g. satellite, sensor instrument) or spatio-/temporal coverage,..) Used for product discovery EO products are individual product instances e.g. one 15 min “image” product from MSG Seviri, e.g. 3 min Metop ASCAT product, Metadata more geared to technical details of the acquisition: orbit, calibration, quality, processing, etc Used for data access
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Background: Collection and Product Metadata ctd.
Collection Metadata: Based on ISO Product Metadata: Based on OGC Earth Observation Profile (OGC r4) of Observations and Measurements (ISO )
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Assumptions for the Study
WIGOS is not meant to describe single EO products (instance) The WIGOS repository is not meant to receive one metadata file every 3 min with individual instance parameters The WIGOS repository contains information about the observation “technical” characteristics WIGOS is more than discovery metadata It contains a more exhaustive product description for satellite products (instrument, measurement technicalities)
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O&M EOP delegates elements to ISO 19115-2 via parentIdentifier link
Considerations O&M EOP delegates elements to ISO via parentIdentifier link Consider ISO for those parts Validate that the most important metadata model elements of O&M EOP can be mapped with WIGOS Validate that the minimal required ISO metadata elements can be mapped with WIGOS For cross checking we also defined mappings from WIGOS to EOP + ISO: ZPgPG62775RIsh-QMcEbaIHYPUCY/edit#gid=
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Approach – Mapping ISO19115-2 to WIGOS
Check mapping ISO19115(-2) to WIGOS: this included: Check if minimal required ISO19115 (not -2!) elements covered: Mostly covered*: abstract/title/keywords/topicCategory (very rudimentary mappable to: 1-01/2-01/2-02/..), originator (10-01), processor (7-02), spatialExtent (1-04), temporalExtent (1-03), constraints (9-02), operationStatus (3-09), creation/revision/publication- date (7-03) Not covered: Metadata on metadata: metadata language, datestamp, contact point, metadata standard (name/version) Checking if minimal important ISO elements are covered: Covered*: satellite/satelliteDescription (mapped to 3-06/3-03), instrument/instrumentType (mapped to 5-09 / 5-02) * in () you´ll find the numbers of the WIGOS elements
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Approach – Mapping O&M EOP to WIGOS
Mapping OGC O&M EOP to WIGOS: we checked if (minimally) the most important metadata ele- ments of EOP O&M can be mapped to WIGOS metadata. URL: AlxJl-O5D2SAn7vHiveigYafe4w/edit#gid= EO product specific metadata elements were not checked as it is not the target to describe single EO products
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Conclusions – Missing Information (1)
QualityInfo is insufficiently considered in WIGOS productQualityDegradation, productQualityStatus fields missing Maybe only valid for product instances ? Orbit Information platformOrbitType may be interesting to include (GEO/LEO) Few elements should be checked if those may make sense to include in WIGOS like: orbitDuration, orbitDirection
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Conclusions – Missing Information (2)
Links to previews could be interesting BrowseImage, QuickLook, Thumbnails MaskInformation missing ? Two kinds of identifier should be added into account: a URI (for being able to deference and link the dataset) and a Digital Object Identifier Elements describing data access are fully missing E.g: links (URLs) to direct downloads or access points Reserved to discovery metadata ?
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Conclusions – Questions
Are more elements to describe Abstract and keywords needed ? In OGC/HMA this is usually overtaken by ISO19115 elements. But it stays minimal to not overload the product metadata It might be important to have link to related information. In HMA EOP there are: parentIdentifier: used to link to the collection identifier linkedWith: used to link another EO product (e.g. ERS1 and ERS2 interferometric pair) subsetOf: used to link to the “father” EO product composedOf: used to link to EO product that is part of this EO product
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WIGOS abstract mode can be used to describe Earth Observation Products
Conslusions WIGOS abstract mode can be used to describe Earth Observation Products What about WMDR the metadata exchange format ? To be verified in 2017 by CGMS Task Force on Metadata Implementation
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Thank you ! Questions ?
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More details below are provided if necessary
Appendix More details below are provided if necessary
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Approach – Mapping O&M EOP to WIGOS
Summary evaluations of mappings (see Fig.) are given in the following for groups of EO metadata elements (aligned with the groups found in OGC r4) eop:EarthObservation eop:EarthObservationMetaData eop:EarthObservationEquipment eop:Footprint eop:EarthObservationResult Per group the status is defined including what is not yet covered so that improvements / extensions are required. * WIGOS element
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Results eop:EarthObservation
The observation core (eop:EarthObservation) is sufficiently covered. eop:EarthObservationMetaData most elements are sufficiently mapped, others are just related to product instances (e.g. acquisitionDate, archivingDate) and are not considered ProcessingInformation is sufficiently mapped. some elements may need to be covered or need improvements e.g. statusSubtype QualityInfo is insufficiently considered in WIGOS, e.g. productQualityDegradation, productQualityStatus, productQualityDegradationTag, productQualityReportURL To decide if this just relates to single Product instances
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Results eop:EarthObservationEquipment
Platform and Instrument/Sensor seem sufficiently be covered. platformOrbitType may be interesting to include (GEO/LEO) Few elements should be checked if those may make sense to include in WIGOS like: orbitDuration, orbitDirection Some acquisition information are too specific for metadata describing collections (more related to single product instances) e.g. orbitNumber or ascendingNodeLongitude sensorSwathIdentifier, sensorWavelengthInformation / discreteWavelengths etc… eop:Footprint is covered 1-04
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Results eop:EarthObservationResult
context is more related to single product instances especially ProductInformation could be skipped if no single product instances shall be described Maybe links to previews (BrowseImage, Quicklook, Thumbnail) could be interesting what about MaskInformation ? General observations Minimally two kinds of identifier should be taken into account: a URI (for being able to deference and link the dataset) and a DOI. The descriptions of different metadata elements need an update when those shall also be applied for EO related information: e.g. description of “platform” to be extended to cover “satellite” Elements describing data access are fully missing For example: general access points (e.g. link to Order App) or links (URLs) to direct downloads could be addressed.
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Results Maybe more elements needed to describe abstract and keywords.
In OGC/HMA this is usually overtaken by ISO19115 elements. Need to be limited to basic information to not overload it especially with regard to the case that in the future WIGOS metadata may also be used to describe single EO products. For the future it would be important to have some hooks to link to related information. In HMA E&P we have: parentIdentifier: used to link to the collection identifier. Could be used in WIGOS to link e.g. to more general information (e.g. CGMS metadata if ISO19115 elements will not be covered) subsetOf: used to link to the “father” EO product (e.g. a phr:Scene is a subset of a phr:DataStrip) composedOf: used to link to EO product that is part of this EO product (e.g. a phr:DataStrip is composed of one or more phr:Scene) linkedWith: used to link another EO product (e.g. ERS1 and ERS2 interferometric pair)
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