coordinate transformation coverage Discussion Papers | OGC

8.12 geographic coordinate reference system

coordinate reference system using an ellipsoidal coordinate system and based on an ellipsoid that approximates the shape of the Earth NOTE A geographic coordinate system can be 2D or 3D. In a 3D geographic coordinate system, the third dimension is height above the ellipsoid surface.

8.13 georeferenced image

image where the image position that corresponds to any ground position covered by that image can be computed using an image geometry model or other coordinate transformation NOTE Most images being exploited are georeferenced, at least approximately. Georeferenced implies that the sensor position and pointing directions at the time of image collection are known, with some degree of accuracy. For a two-dimensional image the normal type, the image coordinate reference system is 2D. However, the ground coordinates are always 3D. The 3D ground coordinates are “projected” into 2D image coordinates using an image projection.

8.14 ground coordinates

coordinates of points measured in a non-image coordinate reference system NOTE The term ground coordinates is used herein to distinguish such coordinates from image coordinates. Even when an image is collected by a near vertical camera, image coordinates are different from ground coordinates

8.15 image

record of the likeness of any features, objects, and activities NOTE An image can be acquired through the sensing of visual or any other segment of the electromagnetic spectrum by sensors, such as thermal infrared, and high resolution radar. An image can also be acquired outside the electromagnetic spectrum, e.g., sonar and seismic images.

8.16 image archive

repository of image data and some associated metadata

8.17 image catalog

registry of metadata about images

8.18 image compression

operation that, through various techniques, reduces the quantity of stored data needed to represent a digital image © OGC 2004 – All rights reserved 29