Abstract:Aiming to explore results of classification and extraction of forest gaps in forest based on active remote sensing, the classification accuracy and applicability of the threshold method were compared, including the pixeloriented method and the objectoriented method in natural forest and man-made forest based on unmanned aerial vehicle (UAV) light detection and ranging (LiDAR). Maoershan Forest Farm in Harbin, Heilongjiang Province and Wangyedian Forest Farm in Chifeng, Inner Mongolia Autonomous Region were selected as the natural forest experimental site and the manmade forest experimental site respectively. The threshold method, the pixel-oriented method and the object-oriented method were applied to classify the two experimental sites into three classes based on UAV LiDAR acquired, which were forest gap, nonforest gap and others. The research results indicated that the object-oriented method produced the highest classification accuracy and Kappa coefficient in both experimental sites, which were 82.43% and 0.73 in natural forest and 91.74% and 0.88 in man-made forest, respectively. The accuracy and Kappa coefficient of the pixel-oriented method was lower than that of the objectoriented method, which was 76.62% and 0.64 in natural forest and 78.68% and 0.68 in man-made forest. The accuracy and Kappa coefficient of the threshold method had larger difference. It produced the lowest accuracy in natural forest (50.54% and 0.27) and the higher accuracy in man-made forest (79.12% and 0.69). The objectoriented method and the pixel-oriented method were the methods with general applicability in classification of natural forest and man-made forest and could produce ideal accuracy and Kappa coefficient. The threshold method produced lower accuracy in natural forest and was more suitable for classification of man-made forest, forest height of which was similar and where others such as buildings and roads were rare. The best classification method of natural forest was the object-oriented method and the best of man-made forest was the threshold method. The research results provided method reference and technology support for extraction of forest gaps in natural forest and man-made forest.
