observation.xsd

See ISO/DIS 19136 Clause 19.
A GML observation models the act of observing, often with a camera, a person or some form of instrument.  An observation feature describes the "metadata" associated with an information capture event, together with a value for the result of the observation.  This covers a broad range of cases, from a tourist photo (not the photo but the act of taking the photo), to images acquired by space borne sensors or the measurement of a temperature 5 meters below the surfaces of a lake.
The basic structures introduced in this schema are intended to serve as the foundation for more comprehensive schemas for scientific, technical and engineering measurement schemas.