The CEOS-ARD Concept
Analysis Ready Data (ARD) is a term used frequently across the geospatial and remote sensing sector, however, until recently, a clear definition for ARD was not specified. Throughout the last few years, CEOS has worked to help establish the CEOS-ARD concept (formerly CEOS Analysis Ready Data for Land (CARD4L)). CEOS defines ARD to be:
CEOS Analysis Ready Data (CEOS-ARD) are satellite data that have been processed to a minimum set of requirements and organised into a form that allows immediate analysis with a minimum of additional user effort and interoperability both through time and with other datasets.
The concept covers the broad definition (noting that it is not exclusive or prescriptive), Product Family Specification (PFS) with detailed requirements, and product assessments through self-assessments and peer reviews. The PFS and assessments are at the core of the concept. As of September 2023, the PFS cover four optical and three SAR data product types:
- Surface Reflectance
- Surface Temperature
- Aquatic Reflectance
- Nighttime Lights Surface Radiance
- Normalised Radar Backscatter (NRB)
- Polarimetric Radar (POL)
- Ocean Radar Backscatter (ORB)
Additional PFSs currently in development are Geocoded Single-Look Complex (GSLC) Radar, Interferometric Radar (INSAR) and LiDAR Terrain and Canopy Top Height. The SAR team is also developing one combined SAR PFS, which incorporates specifications for NRB, POL, ORB and GSLC.
Standardisation & Industry Engagement
In 2022, the CEOS-ARD Oversight Group was established, primarily to oversee the cross-domain uptake of the CEOS-ARD concept. As one of their first activities, the Oversight Group engaged with standards organisations IEEE and International Organization for Standardization/Open Geospatial Consortium (ISO/OGC), to understand what would be needed to turn the CEOS-ARD framework into official, internationally recognised standards. As a result of this engagement, ISO/OGC have recently formed the OGC ARD Standards Working Group (SWG), who met for the first time at OGC’s 126th Member Meeting in Huntsville, Alabama, USA on June 5, 2023. The group is chaired by Dr. Liping Di from George Mason University and co-chaired by Patrick Quinn, NASA representative to LSI-VC. The SWG is formed of both industry, academia, and CEOS Agency members, making it an ideal way for CEOS to engage with the broader community.
CEOS also recently participated in the ARD23 Workshop, an industry-led event held in San Francisco, May 16-18, 2023. CEOS representatives presented the CEOS-ARD concept and invited industry partners to engage with the process. The workshop provided an opportunity to hear feedback from industry and suggestions for improvements to CEOS-ARD.
Alongside the ARD23 workshop, CEOS representatives met with members of the STAC community to discuss how best to implement SpatioTemporal Asset Catalogs (STAC) into CEOS-ARD datasets to maximise interoperability. CEOS-ARD STAC Extension (available here, currently titled “CARD4L”) have been developed to coincide with CEOS-ARD specifications for surface reflectance, surface temperature, normalised radar backscatter, and polarimetric radar products. Key outcomes from the meeting include working with the STAC community on their efforts to make STAC an OGC Community Standard, mapping existing STAC extensions to consolidate and agree on a clearer structure, working with the WGISS STAC Best Practices team to provide guidance on implementing STAC into CEOS-ARD products, and working with the CEOS-ARD Oversight Group on achieving CEOS endorsement of CEOS-ARD STAC Extensions.
At IGARSS 2023, in Pasadena, California, Andreia Sequira (GA, LSI-VC Co-lead) chaired a dedicated CEOS-ARD session, which was attended by about 40 people, and focused on the processes implemented by data providers to process data to CEOS-ARD standards. Sinergise presented their on-demand processing model on Sentinel Hub, while ISRO and DLR each presented some of the challenges they have faced in reaching the threshold level for CEOS-ARD. Ake Rosenqvist (JAXA) provided an update on the SAR ARD product family specifications, and Ingo Simonis (OGC) discussed the challenges faced with the standardisation of data products. Andreia also presented the below poster, which provided an opportunity for one-on-one discussions with participants about the development of CEOS-ARD.
The Product Assessment Process
For a dataset to be certified as CEOS-ARD compliant, a team from the CEOS Working Group on Calibration & Validation (WGCV) will review and assess the product’s compliance. Data providers first submit a self-assessment, where the provider reviews the PFS alongside their product, and describes how the product complies with each requirement.
Any data provider, public or commercial, is invited to submit a self-assessment. To help streamline the peer review process, the WGCV assessment team has put together a guide to CEOS-ARD self-assessments. Any questions regarding the self-assessment process can be sent to email@example.com. Further information and resources related to CEOS-ARD can be found at ceos.org/ard.