基于ETM^+影像的森林资源信息提取——以黄土高原丘陵沟壑区水土保持林为例

以森林资源遥感分类为切入点,以黄土高原丘陵沟壑区陕西黄龙县境内的水土保持林作为对象,针对ETM+遥感影像在森林信息提取中存在的大量混合像元的问题,引入一种基于针叶林-阔叶林-灌草(C-B-G)模型的混合像元分解方法,通过这种方法,分别得到研究区针叶林、阔叶林、灌草的覆盖图像,并提取出了针阔混交林的分布情况。采用ER-DAS 9.1对分类结果进行精度评价,结果表明针阔混交林的分类精度相对于通用分类方法——监督分类的精度提高了20%,说明该方法可以改善植被信息提取的效果。

Modified method for extraction of watershed boundary with digital elevation modeling

Boundary extraction of watershed is an important step in forest landscape research. The boundary of the upriver wa-tershed of the Hunhe River in the sub-alpine Qingyuan County of eastern Liaoning Province, China was extracted by digital elevation modeling (DEM) data in ArcInfo8.1. Remote sensing image of the corresponding region was applied to help modify its copy according to Enhanced Thematic Mapper (ETM) image抯 profuse geomorphological structure information. Both the DEM-dependent boundary and modified copy were overlapped with county map and drainage network map to visually check the effects of result. Overlap of county map suggested a nice extraction of the boundary line since the two layers matched precisely, which indicated the DEM-dependent boundary by program was effective and precise. Further upload of drainage network showed discrepancies between the boundary and the drainage network. Altogether, there were three sections of the extraction result that needed to correct. Compared with this extraction boundary, the modified boundary had a better match to the drainage network as well as to the county map. Comprehensive analysis demonstrated that the program extraction has generally fine precision in position and excels the digitized result by hand. The errors of the DEM-dependant extraction are due to the fact that it is difficult for program to recognize sections of complex landform especially altered by human activities, but these errors are discernable and adjustable because the spatial resolution of ETM image is less than that of DEM. This study result proved that application of remote sensing information could help obtain better result when DEM method is used in extraction of watershed boundary.

Pattern Dynamics of Thermal-environment Effect During Urbanization:A Case Study in Shenzhen City,China

The thermal-environment effect exists in the field of rapid urbanization. It has adverse effects on the urban atmosphere, re- gional climate, energy consumption, and public health. Shenzhen, a representative of rapidly urbanizing cities in China, was selected as a case for pattern dynamics analysis of the thermal environment. The surface temperature was acquired from the thermal infrared data of Landsat TM and ETM＋ images in 1986, 1995, and 2005 by Jim6nez-Mufioz and Sobrino＇s generalized single-channel method, which was used in assessing the distribution and spatial patterns of the thermal environment. The relative thermal environment curve （RTC） was combined with Moran＇s I analysis to assess the pattern dynamics of the thermal environment in different urbanization periods. Moran＇s I index and the RTC represent a process of aggregation-fragmentation-aggregation, which shows the aggregation pattern of a decrease during the rapid urbanization period and then an increase during the steady urbanization period. High-temperature areas gradually ex- panded to a uniform and scattered distribution in the rapid urbanization period; while the high thermal-environment effect was gradually transformed into a steady spatial pattern in the stable urbanization period. To characterize the increasing development in this multiple- center city, we chose profiles along an urban-development axis. The results suggest that heat islands have expanded from internal urban to external urban areas. Four profiles were obtained showing differences in shape due to spatial differences in the process of development.

Recent Changes Occurred in the Terminus of the Debriscovered Bilafond Glacier in the Karakoram Himalayas Using Remotely Sensed Images and Digital Elevation Models(1978-2011)

Recent changes occurred in terminus of the debris-covered Bilafond Glacier in the Karakoram Range in the Himalayas, Northern Pakistan was investigated in this research. Landsat MSS, TM and ETM+ images were used for this study. Digital elevation models derived from ASTER GDEM and SRTM were also utilized. Visible, infrared and thermal infrared channels were utilized in order to get accurate glacier change maps. Three methods were tried to map this debris-covered glacier in this research. The glacier has been mapped successfully and the changes in the glacier terminus from 1978 to 2011 have been calculated. Manual, semi-automatic and thermal methods were found to give similar results. It was found that the glacier has undergone serious ablation during this period despite of the fact that many of the larger glaciers in the Hindu Kush and Karakoram mountain regions in the Upper Indus Basin were reported to be expanding. The terminus has been moved back about 600 meters during this period and there was an abrupt change in the glacier terminus during 1990-2002. We propose that debris thickness is not the only factor that influences the glacier ablation but the altitude of the debris-covered glacier as well. Many glaciers in the Karakoram region reported to be expanding were having higher altitudes compared to the study area.

Evaluation on the Two Filling Functions for the Recovery of Forest Information in Mountainous Shadows on Landsat ETM + Image

In general,topographic shadow may reduce performance of forest mapping over mountainous regions in remotely sensed images.In this paper,information in shadow was synthesized by using two filling techniques,namely,roifill and imfill,in order to improve the accuracy of forest mapping over mountainous regions.These two methods were applied to Landsat Enhanced Thematic Mapper (ETM +) multispectral image from Dong Yang County,Zhejiang Province,China.The performance of these methods was compared with two conventional techniques,including cosine correction and multisource classification.The results showed that by applying filling approaches,average overall accuracy of classification was improved by 14 percent.However,through conventional methods this value increased only by 9 percent.The results also revealed that estimated forest area on the basis of shadow-corrected images by 'roifill' technique was much closer to the survey data compared to traditional algorithms.Apart from this finding,our finding indicated that topographic shadow was an accentuated problem in medium resolution images such as Landsat ETM+ over mountainous regions.

Analyzing the Relationship between Urban Patterns and Land Surface Temperature Using WorldView-2 and Landsat-ETM＋

Global climate destabilization as a result of the increased urbanization is one of today＇s most urgent issues. The detected urban heat island phenomenon in urbanized areas, combined with the decreased vegetation and the anthropogenic heat discharge, is an example of this climate change and in order to take proper actions to reduce this effect, the urban environmental analysis is more than necessary. This paper aims at analyzing and exploring the relationship between land uses of a densely populated urban area with the LST （land surface temperature） combining with WorldView-2 and Landsat ETM＋ satellite imagery. The available thermal band of the Landsat image is used to extract surface temperatures of the study area on a hot summer day. Continuously, the high resolution satellite image of WorldView-2 is used for extracting the land uses. Zonal statistics were applied highlighting the zones with high and low average temperatures. Additional statistical tests （correlation analysis, analysis of variance-ANOVA, etc.） were applied, for evaluating the interaction between the temperature results with the land use types.

基于局部差异加权的遥感影像融合方法研究

在分析现有遥感影像融合方法的基础上,针对多源遥感影像之间的地物差异,提出了一种基于局部差异加权的融合方法(local difference powering fusion,LDPF)。实验表明,该方法能在提高空间分辨率和保持光谱特征的同时,较好地解决空间信息差异的问题。

Atmospheric correction of remote sensing imagery based on the surface spectrum’s vector space

Due to the atmosphere effect,the qualities of images decrease conspicuously,practically in the visible bands,in the processing of earth observation by the satellite-borne sensors.Thus,removing the atmosphere effects has become a key step to improve the qualities of images and to retrieve the actual reflectivity of surface features.An atmospheric correction approach,called ACVSS(Atmospheric Correction based Vector Space of Spectrum),is proposed here based on the vector space of the features' spectrum.The reflectance image of each band is retrieved first according to the radiative transfer equation,then the spectrum's vector space is constructed using the infrared bands,and finally the residual errors of the reflectance images in the visible bands are corrected based on the pixel position in the spectrum's vector space.The proposed methodology is verified through atmospheric correction on Landsat-7 ETM+ imagery.The experimental results show that our method is more accurate and the corrected image is more distinct,compared with those offered by current popular atmospheric correction software.