Sensor Observation Service

The Sensor Observation Service ( SOS) is a web service for querying real-time sensor data and sensor data time series. The sensor data offered include on the one hand descriptions of sensors themselves, which are encoded in the sensor Model Language ( SensorML ) and the measured values ​​, which are encoded in the Observations & Measurements (O & M) format. The web service and both file formats are open standards and defined in the same specifications of the Open Geospatial Consortium ( OGC). If the SOS is transactional (SOS -T), new sensors can be registered via the service interface and then pasted readings. The SOS can provide data from both on-site and from remote sensing sensors. In addition, the sensors can be both mobile and stationary.

Since 2007, the SOS is an official OGC standard. The advantage of the SOS is that sensor data - of any kind - are available in a standardized format and standardized operations on the Internet and thus the web-based access is simplified on sensor data. Since the SOS is an OGC standard, it also allows for easy integration into existing infrastructures Geoservice or general geographic information systems.

Operations

The SOS has three so-called core operations that must be offered by each SOS implementation. The GetCapabilities operation allows you to query a service description with information about the service interface and the sensor data offered. For the operation, the GetObservation function is probably the most important. This can be readings from sensors to query. DescribeSensor the function returns detailed information of a sensor or a sensor system, the data provided, and the processes, which process the data back.

Core operations (core sections):

  • GetCapabilities - returns an XML service description, on the one hand information about the interface ( offered surgery) as well as about available sensor data, such as time, are available for the sensor data, sensors that produce the measured values ​​, or phenomena observed (e.g., air temperature ) which.
  • GetObservation - pull - based query of observed values ​​with metadata; the measured values ​​and their metadata are returned in the Observations & Measurements format ( O & M).
  • DescribeSensor - provides sensor metadata in SensorML back coded. In the SensorML record are usually the ID of the sensor containing the position and observed phenomena. In addition, other information, as described, for example, calibration data.

Transactional operations ( Transactional profiles):

  • Register sensor - makes it possible to register a new sensor in a running SOS
  • Insert Observation - allows you to insert data for registered sensors in the SOS

Advanced operations ( Enhanced Profile ):

  • GetResult - offers the opportunity for consistent metadata ( eg sensor, observed object ) for a series of measurements, query only the measured value without the metadata
  • GetFeatureOfInterest - provides the geoobject whose properties are monitored by sensors in the Geography Markup Language ( GML) encoding back
  • GetFeatureOfInterestTime - provides time periods in which measured values ​​for an observed object in the SOS are available.
  • DescribeFeatureType - returns the type of the observed Geoobjekts back (XML Schema )
  • DescribeObservationType - returns the type of observation back ( XMLSchema, eg om: Measurement)
  • GetObservationById - allows the query of an observation by ID
  • DescribeResultModel - provides the XML schema of the measured value; this is mainly for complex measurements, such as multi-spectral data of importance.

Using the methods

In addition to the core operations, there are additional operations that do not necessarily have to be implemented. In many projects, only the Insert Observation method is for the time being in addition to the basic functions used in addition. This makes it possible einzupflegen of external data into the current Sensor Observation Service. The data will be strictly in accordance with the O & M specifications embedded in an XML file passed to the SOS.

Find services and sensors

If a potential user searching for sensors, this is usually done on a high level of abstraction. The search is either a sensor-related position, or carried out based observation. A user searches in general sensor- received if he already has knowledge of sensors in an area and now want to query their readings. Observation relation is looking for a user whenever he wants to get sensor data in a specific area. He should then all the measurements, which belong to a certain phenomena are displayed.

Terminology to the Sensor Observation Service

The OGC has - not only in the context of the SOS - own well-defined terminology. For better understanding, here are some important terms:

Software

The SOS is a standard of the OGC and ultimately defines only the service interface, but as the service is not implemented. There are currently several open source implementations of the service:

  • Java SOS implementation of 52 ° North
  • Java SOS implementation within the framework of the deegree company lat / lon
  • The C implementation of SOS in MapServer
  • Java, Perl and Python implementations of SOS OOSTethys project
Keyhole Markup Language Styled Layer Descriptor Web Coverage Service Web Processing Service
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