Picture histogram and interpretation of digital orthophotos in forest management

Abstract

The paper presents the possibilities of using histograms of a stand scene and visual interpretation of a digital orthophoto to estimate stand density and condition. Black-and-white aerial photographs with an approximate scale M /spl ap/ 1:20,000 and 60% overlap, obtained during cyclical survey of the Republic of Croatia, were used for this purpose. According to research results, there are three basic forms of histograms which may be associated with the corresponding density categories. They may also purposefully be used to estimate the density and condition of a stand. Furthermore, the form of histograms of stand scenes corresponds to stand descriptions. Stands with normal and poor density may be defined with digital value classes, while stands with density between 0.50 and 0.80 cannot be specified accurately. Ocular assessment of density based on stand canopy was also made, and firm correlation with concrete density was established, i.e. it was found that canopy may be used as a measure of density.