%0 Research article
%T Change detection in boreal forests using bi-temporal aerial photographs
%A Hyvönen, Pekka
%A Anttila, Perttu
%D 2006
%J Silva Fennica
%V 40
%N 2
%R doi:10.14214/sf.345
%U https://silvafennica.fi/article/345
%X Increased need for timely forest information is leading to continuous  updating of stand databases. In continuous updating, stand attributes  are estimated in the field after an operation and stored in databases.  To find the changes caused by operations and forest damage, a  semi-automatic method based on bi-temporal aerial photographs was  developed. The test data were classified into three classes: No-change  (952 stands), Moderate-change (163 stands) and Considerable-change (44  stands). The aerial photographs were acquired in years 2001 and 2004  with almost the same image specifications. Altogether 110 features at  stand level were extracted and used in change detection analysis. The  test data were classified with stepwise discriminant analysis. The  overall accuracy of classification varied between 75.3 and 84.7%. The  considerable changes were found without error, whereas the  Moderate-change and No-change classes were often confused. However,  84.2% of thinned stands were classified correctly. The best accuracy in  classification was obtained by using the histogram and textural features  extracted from the original, uncorrected images. Radiometric correction  did not improve the accuracy of classification. Soil type,  characteristics of the growing stock and the location of a stand in an  image were found to affect the change detection. Before the method can  be applied operationally, issues related to, e.g., confusion between  No-change and Moderate-change must be solved.