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Title: Estimating uncertainty in map intersections
Author: McRoberts, Ronald E.; Hatfield, Mark A.; Crocker, Susan J.
Publication: In: McRoberts, Ronald E.; Reams, Gregory A.; Van Deusen, Paul C.; McWilliams, William H., eds. Proceedings of the eighth annual forest inventory and analysis symposium; 2006 October 16-19; Monterey, CA. Gen. Tech. Report WO-79. Washington, DC: U.S. Department of Agriculture, Forest Service. 289-296.
Abstract: Traditionally, natural resource managers have asked the question "How much?" and have received sample-based estimates of resource totals or means. Increasingly, however, the same managers are now asking the additional question "Where?" and are expecting spatially explicit answers in the form of maps. Recent development of natural resource databases, access to satellite imagery, development of image classification techniques, and availability of geographic information systems has facilitated construction and analysis of the required maps. Unfortunately, methods for estimating the uncertainty associated with map-based analyses are generally not known, particularly when the analyses require maps to be combined. Motivated by the threat of the emerald ash borer in southeastern Michigan, the number of ash trees at risk was estimated by intersecting a forest/non-forest map and an ash tree distribution map. The primary objectives of the study were to quantify the uncertainty of the estimate and to partition the uncertainty by source. An important conclusion of the study is that spatial correlation - an often ignored component of uncertainty analyses - made the greatest contribution to the uncertainty in the estimate of the total number of ash trees.
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