研究目的
To identify suitable variables and algorithms for classifying land cover, forest, and tree species using high spatial resolution images, specifically exploring the incorporation of different seasonal data, combination of variables, and different classifiers.
研究成果
The research demonstrated that combining multi-seasonal images and multiple data sources significantly improves land cover and forest classification accuracies. MLC performed best with spectral data alone, while machine learning algorithms like RF and SVM excelled with multiple data sources. No single algorithm or data source provided the best accuracy for all tree species, indicating the need for a comprehensive classification procedure tailored to specific species. Future work should focus on deep learning and hierarchical approaches for better tree species mapping.
研究不足
The study used images from different years (2015 and 2017) for leaf-off and leaf-on seasons, which may introduce temporal inconsistencies. The accuracy of DSM extraction had mean errors of 4.47 m and 3.75 m for leaf-on and leaf-off seasons, respectively. The RCH feature did not represent true canopy height for evergreen forests. The study area was limited to a specific forest farm in China, and results may not be generalizable to other regions. The object-based segmentation required parameter optimization, which is subjective and time-consuming.
1:Experimental Design and Method Selection:
The study used a comparative analysis of six classification algorithms (MLC, kNN, DT, RF, ANN, SVM) with different data scenarios (leaf-on, leaf-off, combined seasons) and variable categories (V1: spectral bands, V2: V1 plus texture, vegetation indices, segmented shapes indices, and topographic variables, V3: V2 plus RCH features).
2:Sample Selection and Data Sources:
Field survey data from 112 sites in Wangyedian Forest Farm, China, were collected and digitized, with over 1000 samples covering 13 land cover types. ZiYuan-3 satellite data from February 2015 (leaf-off) and September 2017 (leaf-on) were used, including multispectral, panchromatic, and stereo images.
3:List of Experimental Equipment and Materials:
ZiYuan-3 satellite data, eCognition software for segmentation, ENVI and Weka software for classification, Geomatica PCI software for DSM extraction, R software for variable selection.
4:Experimental Procedures and Operational Workflow:
Data preprocessing (atmospheric and topographic correction, data fusion), extraction of variables (spectral, spatial, temporal, height-based, topographic), segmentation using eCognition, variable selection with RF, classification with six algorithms, accuracy assessment using error matrices.
5:Data Analysis Methods:
Overall accuracy, kappa coefficient, user's and producer's accuracies, and tree species mapping accuracy (TSMA) were calculated from error matrices.
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