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Geographic Video Content

information cameras ground based

Definition: Geographic video content includes both spatial and temporal geographic characteristics acquired through ground-based or non-ground-based cameras.

Geographic Information Systems (GIS) incorporate three key types of geographic information: spatial information , representing areas and entities on a map, tabular information , representing related information about these areas and entities, and image information of these areas and entities, such as satellite images, aerial photographs, and the like. This information is combined into progressive layers or slices to provide the user with better understanding of a location for various purposes, such as finding the best physical location for a new road or calculating crop rotation patterns to prevent cross-contamination of genetically-modified crops. However, whereas the capture and use of this information within GIS is now well understood, exploiting both the spatial and temporal geographic characteristics of video footage proves more challenging. Geographic video footage can be acquired through ground-based or non-ground-based cameras, which may have a fixed target or be roving , e.g. CCTV (closed-circuit television) systems, low earth orbit spy satellites, police helicopter cameras, underwater cameras, electronic news gathering video systems, and so forth. Non-ground-based cameras enable the acquisition of video footage that shares similar geographic ground coordinates but has differing height information, e.g. a spy satellite compared with an underwater camera mounted on a remotely-operated vehicle, both observing an area of seawater. Roving cameras enable further possibilities. For example, whereas a fixed CCTV camera will always capture imagery from the same geographic area, cameras mounted to aircraft can track a subject in motion or follow stationary objects that extend over large areas, such as railway or power lines.

Advanced use of geographic video content requires complex georeferencing and visualization techniques. Strip maps have proved popular for visualizing footage from aerial videography , which yields reconnaissance video of a particular geographic area. The strip map is created by placing video images adjacently to create a map of the entire area. This approach has been used in a wide range of applications, from automated road determination to the construction of panoramic video sequences . Comprehensively georeferencing this video footage enables strip-map-like constructs to be implemented within four-dimensional virtual environments that the user can then interactively explore. Such georeferencing requires the following : longitude, latitude and height to provide a position in three-dimensional space, the camera’s pitch, roll , and yaw to specify how it is mounted at this position, and focal length, target height and target width to accurately specify the field of view. With this information, any camera in any situation capturing any imagery as its target can be fully georeferenced. Furthermore, combining this metadata with conventional multimedia content metadata enables advanced multimedia environments, which have both geographic and semantic knowledge of their content. The MPEG-7 standard is one positive step in this direction since it enables geographic metadata to be represented alongside, and cross-referenced with, multimedia content metadata.

Geological Photography - History of, Photography in the Field, Photography in the Laboratory [next]

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