Takeaways from satellite interoperability workshop

October 30th, 2018, Published in Articles: PositionIT

During August more than 100 leaders from the geospatial industry, government, and NGOs gathered at the USGS to discuss one of the biggest questions facing the earth observation field: is the data from different satellites “interoperable,” or exchangeable, with one another? How much effort are we spending trying to make them appear interoperable? How much of this work constitutes getting data ready for analysis? Is analysis-ready data (ARD) the same thing as interoperable data?

Despite the incredible power of satellite imagery, it remains a relatively niche data source because of the difficulty in turning raw pixels from different sources into actionable insight. Even the most seasoned satellite data users are forced to search for data across different locations and massage the imagery in order to perform analysis, and there is no standardised definition of “analysis-ready data”, or ARD, to which practitioners adhere.

This lack of standardisation is even more of an urgent issue as vast archives of EO data head into advanced machine-learning-based pipelines for data mining, where lots of computing resources are wasted effectively harmonising the data, but result in non-portable models and classifiers.

Convened by Radiant.Earth and sponsored by a host of companies, including Planet, the workshop spanned three days, during which attendees discussed different definitions and approaches to ARD and interoperability.

One of the recurring questions during the workshop was how ARD is defined and how it relates to interoperability, whether on the commercial or government side. Although a consensus on standards where not reached in the three days, what became clear was the vast amount of de facto “readying” and harmonising of data happening behind the scenes. Commercial and academic players were candid in describing their challenges and obstacles in creating fusion products. The amount of duplicated work was at times staggering, but hinted at a wealth of opportunities ahead.

ARD and interoperability require standardisation.

ARD and interoperability require standardisation.

One of the first steps toward interoperability is something called the SpatioTemporal Asset Catalog (STAC). The product of a number of collaborative sprints, STAC is essentially a more streamlined way to search for data across providers. More work on STAC is expected in the coming months, and because it sits in the open source software tradition, users drive definitions of standards. When it comes to ARD and interoperability, in contrast, public missions have an outsize effect on cost and schedule considerations for commercial providers of fusion products. This has traditionally discouraged the commercial sector from leading implementations of standards, which was what partly motivated the workshop discussions: the need for more industry-driven collaboration.

Overall, there was broad agreement that standardisation is needed and reaches into previously unaddressed areas, like global georeferences or provisioning SLAs between providers of data. Attendees discovered that all of them are solving similar problems over and over with little channels for consolidation and peer review. There was also consensus that no simple definition of ARD can exist without the definition of standardised families of applications (e.g., analysis-ready data could be ready for a surveyor, but maybe not for a farmer).

This means that ARD ought to open up a more expansive definition of data that overlaps with rich metadata, like radiometric and geometric covariance such as precise camera models or point-spread-functions. To explore this idea, however, requires shifting the framework from one in which data transforms along a pipeline to one in which the core data is precisely defined and constant and the contextual metadata is enriched into more complex products instead.

Key takeaways included:

  • Interoperability is a measurement of quality: The way that practitioners assess if data is good is by comparing it to another source of known quality, like Landsat or Sentinel data. It is core to what makes data usable or ready-for-analysis.
  • ARD is not the same as interoperability: While the terms are often used interchangeably, the processes that make data ready for analysis are not necessarily what make it interoperable. Sentinel and USGS have ARD products that are not directly interoperable until you harmonise around either standard.
  • ARD and interoperability require standardisation: In practice, making data ready for an analysis – which is yet to be defined – hinges on precisely defining standards for the behaviours of the resulting products.
  • Standardised ARD will be a cornerstone of commercial data: Creating harmonised data around standards is something that commercial providers must invest in and open up. (Providing data in a form that is seamlessly integrated with public data is a cornerstone of Planet’s product roadmap for 2018-2019.)
  • Harmonisation of industry roadmaps and SLAs will be needed: Aligning the readiness of different levels of processing, new mission concepts of operations, launch manifests as well as the implementation of standard will happen over time, but more complex products require that this happens in a coordinated fashion. You can combine products that are not available at the same time in a given year or even at the same time during the day after its acquisition.

Some attendees left planning to embrace STAC as a standard in commercial platforms as well as OpenDataCube and other standards that already exist. Working groups are planned to start harmonisation in the open-source context; government players are taking their enthusiasm back to their agencies; and groups like Open Geospatial Consortium are folding the workshop outcomes into future publications.

There was also renewed enthusiasm to get behind the efforts of USGS and ESA in aligning industry-wide standards around upcoming Sentinel and Landsat products such as Level 2 ARD and Collection 2 Landsat.

(This article by Planet was first published here, and is republished here with permission.)

Contact Trevor Hammond, Planet, trevorhammond@planet.com

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