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O3S Use Case 1


Open-standard Online Observation Service

O3S Demonstration Use Case 1: ENVISAT ASAR Referenceable Grid Coverage Download

Below the O3S Demonstration Use Case 1 (UC1) is described in more detail. Please refer to the O3S document deliverables "O3S Demonstration Use Case 1" (D7.1_O3S_UC1), "O3S Demonstration Use Case 2" (D7.2_O3S_UC2), and "O3S Demonstration Use Case 3" (D7.3_O3S_UC3) for further details and information about the other two O3S Demonstration Use Cases.

UC1 follows data access requirements formulated by scientist of the company ENVEO, who are coordinating the EC's GMES Downstream Service CryoLand. The O3S project builds on experience from previous prototyping activities by ENVEO.

It will demonstrate the usage of ReferenceableGridCoverages within DatasetSeries including sub-setting in front of an archive consisting of 10-15 ENVISAT ASAR products provided by ESA.

The original Use Case idea included the generation of snow maps using Web Processing Services (WPSs) and interfacing ESA's G-POD infrastructure. However, this part of the UC was de-scoped at the PDR although some parts of this document still refer to the snow map generation.

The usage of WCS and EO-WCS is demonstrated and validated in all tree use cases but with different focus concerning WCS and EO-WCS concepts and archive access.

UC1 shall demonstrate and validate the usage of Referenceable Grid (satellite image geometry) data opposed to Rectified Grid (geo- or orthorectified) data. The terms "Referencable Grid" and "Rectified Grid" are technical terms in the WCS specification and denote, in this EO context, georeferenced and geocoded satellite image geometries, respectively.

It shall also demonstrate the usage of the concept of Dataset Series which is a technical term in the EO-WCS specification and denotes, in this EO context, 3-D collection as timeseries of 2-D single scenes.

Various applications like the snow map generation procedure rely on accurate SAR input data which is not geo- or orthorectified but still in the original radar (ground or slant range) image geometry. In the O3S project the input to the generation chain shall be generalized from today's stripe- or scene-based input to a coverage-based one (see definition of "Coverage" in O3S Glossary) using OGC's WCS interface.

It is anticipated that the coverage-based data access and the OWS-based interoperability is more convenient and better suited for automation compared to currently used primitive file-based access. Advantages include the possibility of fast previewing and easy sub-setting of the data, resulting in smaller and faster downloads since only the needed data subsets are transferred. Especially in cases when extended regions need to be mapped (e.g., pan-European area) and when the processing chain is split among different operators (as envisaged, e.g., in the context of GMES).

Please find below some UML diagrams showing the UC1. The first is an use case diagram showing all the smaller use cases contained in UC1. The user actions are detailed in the activity diagram and the first sequence diagrams. The operator actions are detailed in the second sequence diagram.

Use Case diagram for the O3S Demonstration Use Case 1
Use Case diagram for the O3S Demonstration Use Case 1

Activity diagram for the user of the UC1 app
Activity diagram for the user of the UC1 app

Sequence diagram for the UC1 user: EO-WCS interactions
Sequence diagram for the UC1 user: EO-WCS interactions

Sequence diagram for the UC1 operator: Configure DatasetSeries
Sequence diagram for the UC1 operator: Configure DatasetSeries

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