面向对象的高分辨率遥感影像分类在卫片执法中的应用研究

近年来,随着我国城市化进程不断向前迈进,城市用地日趋紧张起来,在这样的背景之下,出现了诸多的违法用地、建设等事端。近年来,为了有效地打击此类的违法行为,确保我国土地使用更加科学、合理,有关部门逐渐在对土地动态监测的过程中采用了高分辨率遥感影像分类技术。本文基于此,分析探讨了面向对象的高分辨率遥感影像分类在卫片执法中的应用。

Identifying Alpine Wetlands in the Damqu River Basin in the Source Area of the Yangtze River Using Object-based Classification Method

Alpine wetlands are very sensitive to global change, have great impacts on the hydrological condition of rivers, and are closely related to peoples＇ living in lower reaches. It is essential to monitor alpine wetland changes to appropriately manage and protect wetland resources; however, it is quite difficult to accurately extract such information from remote sensing images due to spectral confusion and arduous field verification. In this study, we identified different wetland types in the Damqu River Basin located in the Yangze River source region from Landsat remote sensing data using the object-based method. In order to ensure the interpretation accuracy of wetland, a digital elevation model （DEM） and its derived data （slope, aspect）, Normalized Difference Vegetation Index （NDVI）, Normalized Difference Water Index （NDWI）, and Kauth-Thomas transformation were considered as the components of the spectral characteristics of wetland types. The spectral characteristics, texture features and spatial structure characteristics of each wetland type were comprehensively analyzed based on the success of image segmentation. The extraction rules for each wetland type were established by determining the thresholds of the spatial, texture and spectral attributes of typical parameter layers according to their histogram statistics. The classification accuracy was assessed using error matrixes and field survey verification data. According to the accuracy assessment, the total accuracy of image classification was 89%.

Land Cover Status in the Koshi River Basin,Central Himalayas

The Koshi River Basin is in the middle of the Himalayas,a tributary of the Ganges River and a very important cross-border watershed.Across the basin there are large changes in altitude,habitat complexity,ecosystem integrity,land cover diversity and regional difference and this area is sensitive to global climate change.Based on Landsat TM images,vegetation mapping,field investigations and 3S technology,we compiled high-precision land cover data for the Koshi River Basin and analyzed current land cover characteristics.We found that from source to downstream,land cover in the Koshi River Basin in 2010 was composed of water body（glacier）,bare land,sparse vegetation,grassland,wetland,shrubland,forest,cropland,water body（river or lake） and built-up areas.Among them,grassland,forest,bare land and cropland are the main types,accounting for 25.83%,21.19%,19.31% and 15.09% of the basin＇s area respectively.The composition and structure of the Koshi River Basin land cover types are different between southern and northern slopes.The north slope is dominated by grassland,bare land and glacier;forest,bare land and glacier are mainly found on northern slopes.Northern slopes contain nearly seven times more grassland than southern slopes;while 97.13% of forest is located on southern slopes.Grassland area on northern slope is 6.67 times than on southern slope.The vertical distribution of major land cover types has obvious zonal characteristics.Land cover types from low to high altitudes are cropland,forest,Shrubland and mixed cropland,grassland,sparse vegetation,bare land and water bodies.These results provide a scientific basis for the study of land use and cover change in a critical region and will inform ecosystem protection,sustainability and management in this and other alpine transboundary basins.