AIR PHOTOGRAPHS AND FOREST SITES: I. MAPPING METHODS ILLUSTRATED ON AN AREA OF THE PETAWAWA FOREST EXPERIMENT STATION

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Abstract
Air photographs have particular advantages in mapping sites because they facilitate the study of the topography and provide a comprehensive view of the tree-cover. These advantages are especially noticeable when absolute site value is considered rather than the productive value in terms of one species.The methods developed make use of two sources of information in the air photographs. These are topography and vegetation. The topographical situation of a specific area, interpreted according to geology and soil, permits an evaluation of site which in many cases is sufficient for all practical purposes. In the other cases, a still closer evaluation may be obtained by also considering the site requirements of the tree species or other vegetation present.At Petawawa the sites had been classified by Heimburger by the Cajander site-type method, so it was desirable to relate the air photographic work to this. With this combination of methods 30 square miles were mapped. Over 16 square miles the photographic data was sufficient, and a check showed an accuracy of 94 per cent. On the remaining 14 square miles tone distinctions were poor and a check showed an accuracy of only 71 per cent. On areas less ecologically complex than Petawawa, even these photos with poor tone distinctions would be sufficient for accurate work.

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