- Bibliographic Information
- Specification Excerpts
- About the Open Geospatial Consortium (OGC)
- Principal References
The Open Geospatial Consortium (OGC) announced that its members have approved version 1.0 of the Observations and Measurements Encoding specification as a final OpenGIS Implementation Standard.
The two-part Observations and Measurements Encoding specification "defines an abstract model and an XML schema encoding for observations and measurements. This framework is required for use by other OGC Sensor Web Enablement (SWE) standards as well as for general support for OGC compliant systems dealing in technical measurements in science and engineering. As a new international consensus standard in an era of increasing scientific cooperation, O&M promises to play an important role in Web-based publishing of real-time and archived scientific data across research disciplines and application domains."
O&M provides standard constructs for accessing and exchanging observations, alleviating the need to support a wide range of sensorspecific and community-specific data formats. Particularly with advancements made during the OWS-3 and OGC Web Services, Phase 4 initiatives, the O&M Observation provides a standard that combines the flexibility and extensibility provided by XML with an efficient means to package large amounts of data as ASCII or binary blocks.
An "Observation" is an action with a result which has a value describing some phenomenon. The observation is modelled as a Feature within the context of the General Feature Model. An observation feature binds a result to a feature of interest, upon which the observation was made.
The aim of the OpenGIS O&M Standard is to "define terms used for measurements and the relationships between them, mainly to improve the ability of software systems to discover and use live and archived digital data produced by measuring systems. When scientists and engineers encode data in O&M, they can easily publish the data (or live data feeds) in catalogs and registries so others can efficiently discover, access and use the data, using relatively simple software. The scope of the specification covers observations and measurements whose results may be quantities, categories, temporal and geometry values, coverages, and composites and arrays of any of these."
The Observations and Measurements specification was produced as part of the OGC's Sensor Web Enablement (SWE) activity. Part 1 was submitted to OGC by the [Australia] Commonwealth Scientific and Industrial Research Organisation (CSIRO) and by Geoscience Australia. Part 2 was also contributed by the UK Council of the Central Laboratories of the Resarch Councils.
OGC's Sensor Web Enablement (SWE) Activity is being executed through the OGC Web Services (OWS) initiatives under the Interoperability Program and the SWE Working Group under the OGC Specification Program. It is establishing the interfaces and protocols that will enable a ?Sensor Web? through which applications and services will be able to access sensors of all types over the Web.
OGC Sensor Web Enablement specifications "make it possible to use a standards-based online catalog to publish information about devices as diverse as radiation counters, anemometers, security cameras, and NASA imaging satellites. These standards also provide the hooks to control sensor and camera platform motion and data collection. The standards are comprehensive enough to work with IEEE smart sensor systems as well as provide for all of the motion control associated with complex Earth imaging satellites. In many cases, owners of these sensors and cameras are making the systems accessible via the Web. By implementing standards in the devices' Web interfaces, disaster managers and first responders can then find and use these devices in a crisis."
The OGC initiatives have defined, prototyped, and tested several components needed for a Sensor Web:
Sensor Model Language (SensorML): SensorML provides standard models and XML schema for describing sensors systems and processes; provides information needed for discovery of sensors, location of sensor observations, processing of low-level sensor observations, and listing of sensor system operations that can be invoked by a client process
Transducer Markup Language (TML): Conceptual model and XML schema for describing transducers and supporting real-time streaming of data to and from sensor systems
Observations and Measurements (O&M): Standard models and XML schema for encoding observations and measurements from a sensor, both archived and real-time
Sensor Observation Service (SOS): Standard Web service interface for requesting, filtering, and retrieving observations and sensor system information
Sensor Planning Service (SPS): Standard Web service interface for requesting user-driven acquisitions and observations. This is the intermediary between a client and a sensor collection management environment
Sensor Alert Service (SAS): Standard Web service interface for publishing and subscribing to alerts from sensors
Sensor Registries: These enable publishing and discovery of sensors and observed values and are implementations of the OpenGIS Catalogue Service Implementation Specification, which has many applications beyond sensor webs.
The Part 1 Observations and Measurements Schema document specifies the core Observations and Measurements model. It discusses observation, measurement, result, procedure, feature of interest, observed property, property type, coverage and related terms, presented using UML class diagrams and in equivalent GML conformant XML serialisations. The scope covers observations and measurements whose results may be quantities, categories, temporal and geometry values, coverages, and composites and arrays of any of these. Annex D of the Schema Specification specifies XML Schema components, in the form of GML Application Schemas that implement the conceptual model in accordance with ISO DIS 19136.
A Sampling Features model is described in the document named Observations and Measurements - Part 2. This refactors elements originally all described as part of the Observations and Measurements best practice paper. "Feature" is an abstraction of real world phenomena. These feature-types are typically associated with making observations producing estimates of property values that are in some way representative of a domain feature. Sampling features embody a sampling strategy that is suitable for the observation procedure and the observed property.
An "Observation" acts as property-value-provider for the feature of interest. There is a related constraint that the observed-property of the Observation must be associated with the feature-of-interest, i.e. it must be a valid property within the definition for the target class of the association end having the roleName featureOfInterest. The feature of interest may be any feature having properties whose values are discovered by observation. In general, this will be of a type from catalogue representing the application domain for an investigation.