Observations and Measurements
Observations and Measurements (O&M) is an international standard which defines a conceptual schema encoding for observations, and for features involved in sampling when making observations. While the O&M standard was developed in the context of geographic information systems, the model is derived from generic patterns proposed by Fowler and Odell, and is not limited to spatial information. O&M is one of the core standards in the OGC Sensor Web Enablement suite, providing the response model for Sensor Observation Service (SOS). Observation schema. The core of the standard provides the observation schema. An "observation" is an act that  results in the estimation of the value of a feature property, and involves application of a specified procedure, such as a sensor, instrument, algorithm or process chain. The procedure may be applied in-situ, remotely, or ex-situ with respect to the sampling location. Use of a common model for observation metadata allows data to be combined unambiguously, across discipline boundaries. Observation details are also important for data discovery and for data quality estimation. An observation is defined in terms of the set of properties that support these applications. O&M defines a core set of properties for an observation: The  key to the model is the division of the observation and its feature of interest, separating the concerns so that the appropriate information associated with the description of each object. This allows a unified treatment of "in situ", "ex-situ", and remote-sensed observations. The observation schema may also be understood as a corollary of the General Feature Model from ISO 19101, providing metadata associated with the estimation of the value of a feature property. The Observation model takes a user-centric viewpoint, emphasizing the semantics of the feature-of-interest and its properties. This contrasts with sensor oriented models  such as SensorML, which take a process – and thus provider-centric viewpoint. Many observations are made to detect the variation of some property in the natural environment, expressed as a spatial function or "field", also known as a "coverage" (ISO 19123:2005). The relationship between observations, features and coverages is explained, in the context of ocean observations and modeling, in a report for GEOSS Architecture Implementation Pilot 3. Sampling features. The standard also provides a schema for Sampling Features. Observations commonly involve sampling of the ultimate feature of interest. Specific sampling features, such as station, specimen, transect, section, are used in  many application domains, and common processing and visualization tools are used. The standard defines a common set of sampling feature types classified primarily by spatial dimension, as well as samples for ex-situ observations. The schema includes relationships between sampling features (sub-sampling, derived samples). The core properties of sampling features are: Implementations. An XML encoding (GML Application Schema) is provided for transfer of data: A JSON encoding is provided for transfer of data: An explicit OWL representation of O&M is available: The W3C Semantic Sensor Network Ontology provides an updated OWL implementation that covers most of O&M Version 2.0  of the Observations Data Model ("ODM2"), developed by the Consortium of Universities for the Advancement of Hydrologic Science, Inc. (CUAHSI) and the Critical Zone Observatory project, adapts O&M. Related documents. O&M is also published as a topic of the Open Geospatial Consortium "Abstract Specification". The previous version of O&M (Version 1) factored the model into two documents: Part 1 described the Observation Schema, and Part 2 described Sampling Features.