RadVAL (Radiometric Validation AnaLytics) Dashboard

The CEOS-PVP (CEOS Product Validation Platform) now hosts the operational (Radiometric Validation AnaLytics (RadVAL) Dashboard service, which allows users to assess the radiometric performance of both public and commercial EO data of interest in real time. The CEOS-PVP began development within the EODH, with the RadVAL tool hosted on the Hub infrastructure, and has grown into a service that aims to benefit the global EO community.

Commercial EO data offer valuable capabilities that complement those provided by Space Agencies, including enhanced temporal coverage and higher spatial resolution. However, these datasets are often perceived by users as less trustworthy. Since the start of EODH, we have worked to address this challenge by developing a QA Service to support rigorous data quality assurance. One of the core EODH services developed for this purpose – RadVAL (Radiometric Validation AnaLytics) Dashboard – has now been adopted by the international community, inspiring the creation of the CEOS-PVP (CEOS Product Validation Platform), for which RadVAL is the first operational service.

Figure 1: Timeseries of Sentinel-2A matchups with two RadCalNet sites (GONA & RVUS), over 2022.

The overall architecture of the CEOS-PVP is split into:

1. Comparison Imagery Database (CID): contains archives of imagery from various missions over a minimal set of established calibration sites, including RadCalNet (RCN) and Pseudo-Invariant Calibration Sites (PICS).
2. RadVAL Comparison Database: contains the outputs of comparisons made between the CID archive mission data and corresponding in-situ reference data.
3. RadVAL Dashboard: populated by the data contained in the RadVAL Comparison Database.

These services are hosted on the EODH infrastructure and as the host of the CEOS-PVP, the EODH has powered the creation and enabled development of this service for CEOS and the global EO satellite community.

Figure 2: Modal popup for one matchup from the timeseries of Sentinel-2A matchups with RadCalNet site GONA.

The CID currently contains both public and commercial data including Sentinel-2, Planet and Airbus Pleiades and Landsat missions (all available in the EODH catalogue), spanning 2021-25. This initial implementation focuses on mission data collected over two RadCalNet sites: Gobabeb, Namibia (GONA) and Railroad Valley, USA (RVUS) and PICS Libya 4, with further information on the sites available on the CEOS-PVP references page. RadVAL aims to visually evidence the 'performance' of these missions against these internationally accepted references, independent of any specific sensor but with the means to identify biases against any sensor in the database. These results, thereby, form the basis for calculating the radiometric QA results that are displayed in the EODH catalogue for a given mission, by comparing the result to their stated radiometric performance.

These comparison results are created from a pipeline of tools developed at NPL, soon to be open source, that find “matchups” when satellites overpass reference sites and process both the satellite and in-situ reference data to make meaningful comparisons; these processes include:

• Spectral band integration of reference data to match the satellite data
• Temporal interpolation of reference data to match the satellite time
• Spatial aggregation of satellite data over the reference region of interest

Future plans for the CEOS-PVP include extending this system to support validation of other data metrics, e.g. geometric validation, surface reflectance, SAR and other sensor products.

Figure 3: Timeseries of PlanetScope matchups with two RadCalNet sites (GONA & RVUS), over 2022, showing over 200 matchups per site.

Using the control panel on the left, select mission, up to two reference sites, bands and date range of interest. The plot will update to display an interactive timeseries of data from matchups according to the selection, where each point refers to a specific matchup between the selected satellite mission and reference site at a particular day and time. If there is a day or matchup that is of special interest, clicking the point will open a modal with more detailed information for the given matchup. It’s also possible to download both the timeseries and matchup data as CSV files via the corresponding buttons.

Visit the CEOS-PVP homepage to find out how to contribute as a data provider, enabling the demonstration of the mission’s radiometric performance and stability to all users in a consistent manner via a range of independent references.