基于遥感和GIS方法的科尔沁沙地边界划定

基于已有文献,依据科尔沁沙地的形成历史与早期分布,确定科尔沁沙地的核心区;以核心区为基础,采用生态学取样方法,选取与核心区边界相交的16个方向上的交叉点为样本,以Landsat-5 TM影像为主要数据源,采用光谱混合模型、穗帽变换等遥感和GIS方法,通过反复试验设定阈值,提取每个方向的分界特征,据此勾画出科尔沁沙地的分界线。此后,进行实地考察和Google Earth高清影像验证,最终确定科尔沁沙地生态区域的边界。结果表明,科尔沁沙地面积为52 300 ± 360 km²,验证后精度在94%以上。研究结果为科尔沁沙地生态恢复与环境整治提供确切基础范围。

Demarcation of the Horqin Sandy Land Boundary Based on Remote Sensing and GIS Technique

Horqin Sandy Land is one of the key regions for desertification prevention and control in China. However, there is lack of exact boundary of Horqin Sandy Land at present. Subsequently, the control and recovery process of environment in this region is affected. Based on both the existing literatures and the formation history and earlier distribution of the Horqin Sandy Land, the core region of the area was first determined in the present study. Then, 26 intersections for the boundary of the core region from 16 directions were taken as the samples using the ecology sampling method. Remote sensing and GIS methods such as linear spectral mixing model and tasseled cap transformation were adopted to process the Landsat-5 TM images in the study area. Three components after tasseled cap transformation (i.e. brightness, greenness and wettness) were used to identify the sample points in the southern nine directions. Based on multiple replication tests, optimal thresholds were selected by obtaining the demarcation characteristics of each intersection sample and the exact boundary of Horqin Sandy Land was delineated accordingly. The linear spectral mixing model was applied in the northern directions because the sandy land and saline-alkali soil were distributed crossly. Combined with the optimal thresholds, the northern part boundary was delineated accordingly. However, this method was inapplicable to two directions and the thematic map of land use types was used to explore the demarcations. Subsequently, field investigation, high resolution images provided by Google Earth and the permanent geomorphology features were combined to confirm each direction of the final boundary of Horqin Sandy Land. According to the verification, the boundary was adjusted slightly. The results showed that the area of Horqin Sandy Land was 52 300 ± 360 km² with the verification accuracy greater than 94%. The errors were caused mainly by the set of threshold values, precision of spectral unmixing results and the resolution of images. The achievements in the present provide the reference to eco-regionalization and environment monitor and ecological restoration in the definite confines in Horqin Sandy Land.