A referenceable grid is associated with information that allows the location of all points in the grid to be determined in a coordinate reference system (CRS), but the location of the points is not directly available from the grid coordinates.

An example is an EO/IR sensor consisting of a rectangular array of light sensing pixels. This OGC Extension provides a set of native referenceable grid elements to be used with the OGC CIS 1.0 coverage standard. It is one of the major outcomes of OGC's Testbed-11.

The Extension includes the referenceable grid elements that were developed originally for GML 3.3 but that were not "in harmony" with CIS 1.0. Further, the Extension allows connections to OGC SensorML 2.0 sensor models from coverages. SensorML 2.0 can be used to describe and share a wide range of sensor models, for example imaging systems located on satellite and airborne platforms.

A simple example of such a description would be a location of a camera, the direction in which it is pointing, as well as details of the camera's imaging system such as the field of view and the number of pixels. This data is thus available for mapping every imaged pixel to a location in an external CRS.

When the Extension is adopted as an OGC standard, OGC imagery standards based on CIS 1.0 (such as GMLJP2 2.0) will be able to contain sensor-models, described with OGC SensorML 2.0, without additional changes. Development work on the open set of possible SensorML-based sensor models to be used with the Extension has begun.

For example, OGC Member KeyW has developed a SensorML-based description of a frame camera strictly based on the Community Sensor Model standards of NGA, while other SensorML 2.0 descriptions of sensor models for imaging systems (for example, the widely used "RPC" replacement model) are in active development.

Geospatial imagery software packages with support for sensor model standards may be easily updated to use OGC sensor model imagery. An open-source package that already has such support for OGC sensor model imagery is OSSIM from osgeo.org.

The OGC Coverage Implementation Schema - ReferenceableGridCoverage Extension is available for review and comment here. Comments can be submitted to [email protected] by 5th January 2017.