A coordinate-free area variance estimator for forest stands with a fuzzy outline

Abstract

Digitized forest maps offer the added convenience of automated area calculation of forest stand polygons. However, the 'actual' stand areas in a forest management operation may deviate from the map value due to the mapping process and the delineation procedures used to identify stand boundaries for management operations. Three sources of area variances of mapped forest stand polygons are considered: the first due to the uncertainty inherent in coordinates, a second due to the linear interpolation between points, and a third due to the basic fuzziness of the boundary. A simple coordinate-free variance estimator is introduced, and predictions made from it are compared to a standard method requiring input of all polygon coordinates. When the coordinate-free variance estimator was applied to a set of simple polygons and a set of 120 natural forest stand polygons, a generally good agreement was found between the results from the two types of estimators. The coordinate-free method is suited for planning purposes when the error components arising from the uncertainties of forest stand areas are needed.