Airphoto Geometry Home Scope of Remote Sensing Remote Sensors Airphoto Interpretation ... Height Calculation a Recommended Readings Campbell, J. (1998) Map Use and Analysis, Chapter 17, pp 268-285. Avery, T. E. and Berlin, G. L.. (1985) Fundamentals of Remote Sensing and Airphoto Interpretation, Chapter 4, pp 71-81. Aerial Photography Airphotos have been an important source of data for mapping since the first decades of the 20th century. Aerial photography can be conducted from space, high or low altitude aircraft, or near ground platforms. Aerial photographs are acquired using a photographic camera an film to record reflected EMR within the camera's field of view. This is an optical-chemical system in which the lens focuses EMR on the film which is coated with a light sensitive emulsion that detects reflected EMR in the wavelength band from 0.3 m m to 0.9 m m, i.e., from the mid ultra-violet to the near IR range. The result is a continuous tone photograph that has high spatial resolution (i.e. shows fine spatial detail) but low spectral resolution (i.e., is sensitive to EMR in a broad spectral band). The entire scene within the camera's field of view is processed instantaneously. However, there distortion in the image due to the fact that it is a perspective rather than planimetric view of the surface. A variety of films and film formats can be used to acquire airphotos. The most common film format is 35 mm which is the standard slide or colour print film. Larger formats such as 70 mm are available and have the advantage of recording greater spatial detail. Most airphotos used for mapping are obtained using a 23 cm x 23 cm metric mapping camera. This large image size maximizes the spatial detail that can be captured on the image. | |
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