DETERMINATION OF THE SPATIAL-DISTRIBUTION OF TREES FROM DIGITAL AERIAL PHOTOGRAPHS

This study examined the possibilities of using computerized digital ae rial photograph interpretation in determining the spatial distribution of trees. The material of the study included eight mapped stands in t he municipality of Hyytiala (61 degrees 50'N and 24 degrees 18'E), in southern Finland. The aerial photographs used were taken in June 1995 at a scale of 1:5000. Two approaches for determining the spatial patte rn of trees were used. Firstly, in the point-process based approach us ed in this study, the individual trees in the digital aerial photograp h were segmented by a robust segmentation method, based on recognition of the pattern of tree crowns with sub-pixel accuracy. Secondly, the crown coverage was determined by region growing segmentation combined with active surface representation. The significance of the difference s in the means of image coverage pattern indices between the various s patial distribution categories was tested with one-way variance analys is. Because the process misclassified clustered spatial patterns as re gular patterns, and regular patterns as random patterns, the usability of digital aerial photographs seems to be limited for the point-proce ss based determination of the spatial pattern of toes if the scale is 1:5000 or less. When image coverage pattern indices were applied, the differences in the means of the spatial distribution categories proved not to be clearly statistically significant due to the great variatio n within classes. However, interpretation of crown coverage could have applications in practical forestry due to the low resolution requirem ents for the images used. (C) 1998 Elsevier Science B.V.