Environmental monitoring infrastructures are increasingly required to support high-frequency sensor data, heterogeneous observation types, and real-time analytics, while ensuring interoperability, scalability, and long-term sustainability. In this context, open standards and open-source technologies play a central role in enabling data sharing across institutions, disciplines, and national boundaries. This workshop introduces istSOS4, an open-source implementation of the OGC SensorThings API, designed for the management, publication, and analysis of spatio-temporal sensor observations. The workshop targets practitioners and researchers involved in environmental monitoring, smart cities, hydrology, climate studies, and geospatial data infrastructures who wish to design interoperable sensor data platforms aligned with FAIR data principles.

Participants will gain both conceptual and practical knowledge on how to structure sensor metadata, ingest observations, and expose time-series data through standardized web APIs. The workshop starts by framing the challenges of modern sensor networks: increasing data volumes, diverse sensor typologies, the need for near real-time access, and the integration of observations with downstream analytics, dashboards, and decision-support systems.

A core focus will be the SensorThings API data model, including key entities such as Things, Locations, Sensors, ObservedProperties, Datastreams, and Observations. Particular attention will be given to
modeling complex environmental monitoring setups, including multi- parameter stations, mobile sensors, and long-term monitoring networks. The workshop will demonstrate how istSOS4 extends and operationalizes
this model in real-world deployments, supporting versioning, quality control, and efficient time-series handling. Through hands-on sessions, participants will interact directly with an istSOS4 instance to:
 Register sensors and monitoring stations,
 Ingest observations via RESTful endpoints,
* Query time-series data using spatial, temporal, and attribute filters,
* Visualize and export observations for further analysis.
The workshop will also cover architectural aspects, including database backends, performance considerations for high-frequency data, and integration patterns with visualization tools, data analytics pipelines, and early-warning systems. Real use cases from environmental monitoring projects (e.g., hydrometeorological networks, water quality monitoring, and climate adaptation initiatives) will be used to illustrate best practices and common pitfalls.
By the end of the workshop, participants will have a clear understanding of how to design and deploy a SensorThings-based infrastructure using istSOS4, enabling interoperable and standards-compliant access to sensor observations.