The process of combining spatial information from two or more maps from the same geographic area to derive a map consisting of new spatial boundaries and entities or themes.

The process of stacking digital representations of various spatial data on top of each other so that each position in the areas covered can be analysed in terms of these data.

An aerial photograph geometrically corrected so that the scale is uniform and distortion is corrected to remove camera tilt and/or ground relief. This is similar to georeferencing an aerial photo, but much more accurate.

An aerial photograph that has the distortion due to tilt, curvature, and ground relief corrected.

A photomap made from an assembly of orthophotographs

Digital or digitized aerial photographs in which the pixels are geometrically rectified and given geographical references. The data structure is raster. An orthophoto map may include details of topography and names.

Image in which by orthogonal projection to a reference surface, displacement of image points due to sensor orientation and terrain relief has been removed.

[coordinate system] An ordinal scale represents the relative order of values but does not record the magnitude of differences between values.

Transparent access to mixed geodata and geoprocessing resources in a networked environment.

A program in which the source code is available to the user for their use and/or modification from its original design free of charge. Open source code is typically created as a collaborative effort in which programmers improve upon the code and share the changes within the community. The result of this collaboration is the fast and affordable development of high quality technologies and software products.

A standard that has members of the GIS user communities cooperatively working to correct and improve spatial data and attributes in exchange for less restrictive uses of the data.

The OGC is a non-profit, international, voluntary consensus standards organization that is leading the development of standards for geospatial and location based services.

Optical element that receives light from the object and forms the first or primary image of an optical system.