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Aerial photogrammetry; Photographic interpretation; Aerial photography in geography


Few events in recent years have stirred public imagination and interest to the degree occasioned by the uses made of aerial photographs in the Cuban affair. The average earth scientist, however, was not taken by surprise since the basic methods, materials and principles involved were not new to him. As a matter of fact, since World War II, aerial photography has become an everyday, virtually indispensable tool to most earth feature and natural resource analysts. In order better to understand the application of aerial photographs to such civil pursuits, it would be well at this point to differentiate the two basic levels of use:

(1). Photogrammetry involves use of highly precise measurements and complicated instrument systems. Among the products of photogrammetry, to list a very few, are highway design, topographic maps, bridge and dam site surveys.

(2). Photo Interpretation involves the extraction of both subjective information and the performance of measurements at a lower level of precision than that essential to the photogrammetrist. Photo interpretation work is usually done by the skilled professional ( e.g., archeologist, forester, geographer, geologist) who utilizes this information to formulate decisions pertinent to his professional activity.

Admittedly, this a gross over-simplification of the distinction between the two levels of activity and precision since there is a certain degree of overlap between the two . As a matter of fact, there are some individuals who are fully qualified to perform both functions. Nevertheless, these basic categories must be recognized in order to indicate to the average subject matter specialist the photo interpretation applications which are available to him directly.

Although the photo interpretation process is basically subjective, both in nature and by definition, a useful degree of quantification is possible. Crude though these measurements and controlled estimates may appear to be to the photogrammetric engineer, they are still suitable and often fully adequate for the purposes of the interpreter. It is doubtful, however, whether these techniques are being put to sufficient use since it is generally estimated that not more than 60% of the useful capabilities of currently-available photo interpretation systems are being realized. It is the purpose of this paper, therefore, to briefly describe some of these measurement techniques, give a few examples in current use and suggest some possibilities for the future.

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