Once the data licence has been selected for the Citizen Observatory, the next step in making it public is to present the data as files in a project website or in open repositories (such as Zenodo). But there are many formats and many data models that can be used. It is important to accompany the data with metadata that describes the data that were collected as well as the data model (what the observed values mean). By distributing the data in a format that is based on an open standard and easy to use, we prevent misinterpretation of the data and facilitate their usage. These files can be accompanied by code to analyse the data (as done by GROW, using Github to share and provide their analysis code on soil moisture for crop growing in Portugal using Python Jupyter Notebooks). In the big data world (where distributing files becomes impractical) it is even better to provide a service that gives access only to the part of the data that users really need. Examples of good and useful services that implement common standards approved by the Open Geospatial Consortium are SOS (Sensor Observation Service) and the SensorThings API. Both fall under the Sensor Web Enablement umbrella, and both allow scientists to retrieve sensor and time-series data filtered geographically, temporally and by data type in JSON or XML format.
Some global platforms where you can share your data:
Ground Truth 2.0, Scent, GROW and WeObserve set up Citizen Observatories that applied these standards and improved data sharing. To allow for the integration of the observations into new models and applications, Scent implemented the Harmonisation platform that later became discoverable through the GEOSS Portal, where Earth Observation data from all over the world can be searched. A combination of shared solutions can cover the needs of more users. Many citizen science data platforms, such as iNaturalist or Spotteron, offer an export to CSV files for occasional downloads, as well as open APIs to create a permanent connection to the data.
Example from the Landsense project
In LandSense, we use the LandSense Engagement Platform to openly share data. We use a distributed system for this. The data from the different citizen science campaigns are hosted with the various project organisations but are accessible on the platform. This also helps to ensure that access to the data can be sustained beyond the lifetime of the project. Landsense data is also uploaded to Zenodo and Pangaea for data access and data preservation purposes. The report “Global dataset of crowdsources for land cover and land use data” illustrates most of the good practices necessary for data sharing. The license is specified as a Creative Commons 3.0 resource. It uses the CC-BY squema and allows any possible usage, including commercial, the only requirement being the need to acknowledge the data sources. The data is accompanied by some medata representing the spatial-temporal context. To access the data, a series of easy to download ZIP files are provided. These zips contain a text data structure that uses tabular data. This data service does not allow for easy subsetting, but given the amount of data contained in the zips, this should not be necessary.