A remote sensing strategy for measuring logging road system length from small-format aerial photography

Small-format aerial photographs (SFAP) can be acquired at a relatively low cost to obtain quantitative data for natural resource applications. A remot e sensing strategy was developed for measuring logging road system length f rom SFAP. Aerial photography, digital image processing, and fieldwork proce dures are described in sufficient detail for natural re source managers to acquire their own SFAP with only basic skills and equipment. An alternative field-based strategy was developed and used to evaluate time, costs, and r elative accuracy of the remote sensing strategy. The field-based strategy w as assumed to consistently produce more accurate measurements of road syste m length than did the remote sensing strategy. The remote sensing strategy was less expensive than the field-based strategy because logging road syste m length can be measured in a shorter amount of time. Error for the remote sensing strategy has an average of 11 percent and can be expected to range from 8 to 14 percent. Accuracy is limited by use of uncontrolled mosaics, l ens distortion, tilt displacement, topographic displacement, and scale vari ation.