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From Earth Observation Applications to Services

One of the primary goals of APEx is to facilitate the transition of Earth Observation (EO) R&D results into reusable, scalable, cloud-based on-demand services. Currently, ESA EOP R&D projects generate a variety of results, including, for example, EO-derived value-added products (raster or vector files, typically level-3 and level-4), workflows and algorithms, or conventional (open-source) desktop software solutions. The APEx Algorithm Services focus on transforming and optimising (i.e., propagating) resulting algorithms, applications, workflows and toolboxes and ensuring their compliance with FAIR data principles. The preservation of these project outcomes is managed through the ESA Project Results Repository (PRR), supported by other APEx services, such as the APEx Data Catalogue.

The vision for the ESA APEx initiative is to adopt FAIR data principles and ensure that project results remain Findable and Accessible and that they become Interoperable and Reusable. For value-added products, this mainly involves ingestion in an ESA-controlled persistent storage solution and exposing these products accordingly (using STAC and other technologies).

Maintaining workflows and algorithms in a FAIR-compliant way requires the adoption of cloud service concepts and implementations. Therefore, APEx envisioned a solution for workflows and algorithms that would make them available in a public cloud (platform) in co-location with the key EO data archives as on-demand services using standardised web service APIs. Users can then trigger these web services with their user-specific parametrisation to produce results for an area and time frame of interest.

However, developing on-demand services can be challenging for many projects and depends heavily on the complexity of a workflow/algorithm and its initial implementation. APEx intends to facilitate the transition to cloud-based services by providing guidelines, best practices, and tools that support EO R&D projects in overcoming these challenges.

The algorithm services support provided by APEx involves various subcomponents, and their relevance depends on a case-by-case basis. The APEx Algorithm Services comprise:

This support can also be visualised in a chart, illustrated in Figure 1. This chart outlines the different pathways for projects to transform and optimise their algorithms into on-demand services using the APEx Algorithm Services.

The main goal of the Algorithm Services is to guide projects in defining their pathway and providing support throughout the various steps. This is accomplished through an initial analysis of the project’s needs, resulting in a tailored pathway that assists in the transformation from source code to on-demand EO services.

flowchart TD ""
    subgraph Legend
      APEX_SERVICE[Activity supported through APEx]
    end
    A((Project Source Code)) --> B{Experiencing Performance Issues?}
    B -->|Yes| C[Algorithm Enhancement Support]
    B -->|No| D{Need help with implementation of APEx Guidelines?}
    D -->|Yes| E[Support for Porting or Packaging Your Algorithm]
    D -->|No| F{Expose your Algorithm as an On-Demand Service?}
    F -->|Yes| G[Support with Deploying your Algorithm on a Hosting Platform]
    G --> H(((On-Demand EO Service)))
    H --> I{Use EO Services for Large-Scale Processing?}
    I -->|Yes| J[Tools and Environment for Upscaling]

    class APEX_SERVICE,C,E,G,J apexService
    click C href "./enhancement.html" _blank
    click E href "./porting.html" _blank
    click G href "./onboarding.html" _blank
    click J href "./upscaling.html" _blank
    classDef default font-size:10pt;
Figure 1: APEx Algorithm Support Pathways