Why InterSensor Service?
In many smart city projects, multiple stakeholders and companies are involved who use their own sensors and IoT devices which are managed by different platforms and APIs. In order to work within a common operational framework, sensor web infrastructures play a key role in providing interoperability between heterogeneous sensor platforms and observations. However, it is unlikely that all stakeholders would be willing to inject their proprietary data into a third-party data storage in the sensor web.
We introduce a new lightweight web service called InterSensor Service, which allows users to connect to multiple IoT platforms, databases and basic files and retrieving their observations without worrying about data storage and the multitude of different APIs. It is a Java application based on the Spring framework and is available as free and Open Source.
Why OGC Sensor Web Enablement?
Sensor Web Enablement (SWE) is an initiative by the Open Geospatial Consortium for realizing sensor web infrastructures. The OGC SWE standards suite comprises well-defined information models such as (i) SensorML, which not only represents sensor description and metadata, but also sensor calibration records and accuracy and precision information, and (ii) Observations and Measurements for describing real-time sensor observations. SWE also provides comprehensive interface models and web services such as Sensor Observation Service (SOS) and SensorThings API for retrieval of sensor descriptions and observations with the help of standardized requests. In comparison to SOS, SensorThings API is a relatively new standard, which is REST-ful, lightweight, and based on JSON. SWE’s wide range of international standards are being used by many agencies worldwide including NASA and the European Space Agency (ESA).
Such sensor web infrastructures establish interoperability of heterogeneous sensors and are considered as one of the keys to work in distributed scenarios. The biggest benefit is that applications can be developed based on these standards without worrying about what different kinds of sensors they use. Multiple sensors can be attached to these infrastructures and their interfaces will always be common for applications.
The architecture of the interSensor Service comprises of the following layers:
The data adapters allows establishing connections to multiple platforms such as ThingSpeak, OpenSensors or Weather Underground. In addition, users can also connect to timeseries data stored in external databases (such as PostgreSQL, Oracle), basic files (such as CSV), Cloud based systems (e.g. Google Fusion Table), GPS Exchange Formats (GPX), and real-time Twitter feeds . While querying, the service opens a data source connection and retrieves the observations based on querying parameters directly from the data source.
Standardized External Interfaces
The retrieved sensor observations can be encoded “on-the-fly” according to international standardized interfaces such as the OGC Sensor Observation Service, OGC SensorThings API, and 52° North Timeseries API. It allows querying and visualizing numerous sensor data streams from heterogeneous sensor platforms with existing sensor web infrastructures.