ABSTRACT
Imagery has long been a primary source of spatial data. In the past, it was aerial imagery that provided an extremely flexible and detailed data source from which a wide range of highly accurate datasets could be generated. Through the photogrammetric processing of aerial images extensive areas could be accurately mapped, thus allowing for more frequent updating and monitoring. With the emergence of remote sensing satellites, the ability to collect spatial data and monitor the environment was further enhanced through the use of rich spectral information from a wide range of passive and active sensors. It would be difficult to imagine how progress could have been made without such imagery in areas such as mapping, agriculture, forestry, geology and hydrology, land cover monitoring, and oceanography.
