The PhenoTandem team developed a co-designed protocol for harmonizing phenological observation from remote sensing and through in-situ observations made by citizen scientists. Remote sensing experts and expert volunteers in phenological observation worked together to come with a final list of suitable species/habitats and a grid map of homogeneous locations to be observed jointly through satellite and in-situ monitoring (Map of Regions of Interest).
In addition, a web browser was prepared (the Catalan Data Cube) containing Sentinel-2 Level 2A data available for Catalonia for the period 2018-2020, as well as the derived vegetation indices (NDVI, EBI). Based on such data, high-level phenological products (green-up, maturity, senescence, and dormancy) were calculated for all Catalonia and years 2018 and 2019 and added to the Map of Regions of Interest.
A citizen science campaign was launched in Autumn 2020 to get in-situ observations from the selected species and sites. A data entry platform was specifically developed to guide users in the identification of the area, species and phenophases observed, directly uploading the observations to the iNaturalist database and linking them to the RitmeNatura citizen observatory.
The project demonstrated that the approach for harmonizing remote sensing and in-situ phenology monitoring seems to work: phenophases observed on the ground apparently fit with the NDVI curves for Sentinel 2 time series in regions where one species is present.
You can take a look at the Vegetation Phenology Observation Protocol and Phenological RS derived high level products here: https://cseol.eu/pilot-projects/phenotandem/
Check out more information about PhenoTandem Pilot Project here: https://ritmenatura.cat/projects/phenotandem/index-eng.htm