Land cover change in Ningbo and its surrounding area of Zhejiang Province,1987～2000

INTRODUCTION Land use and land cover change (LUCC) has become an increasingly important aspect of global environmental change and is a multi-disciplinary subject where geophysicist, bio-physicists and socio-economists meet one another. Land cover is an expression of human activities and, as such, changes with changes in land use and management (Louisa and Antonio, 2001), and land cover change could be regarded as change in biotic diversity, actual and potential productivity, soil quality…     

基于Landsat ETM+影像的福州市地表温度反演研究

以福州市为研究区,采用单窗算法,对Landsat ETM＋第6波段的遥感数据,进行地表温度反演,得到地表温度分布图,分析了地表温度分布规律,并提出减轻热岛效应措施。结果表明：福州市城市热岛效应显著,单窗算法可以较好的反映城市热场的空间分布,地表温度与归一化植被指数（NDVI）有良好的负相关关系,与地面下垫面密切相关。     

东江流域近20年土地利用变化的时空差异特征分析

根据1990年、2000年和2009年3期LandsatTM/ETM影像的土地利用分类结果,综合运用地理信息系统空间分析工具、变化指数对比分析等技术和方法,对东江流域1990年-2009年间的土地利用变化及其区域差异特征进行了分析。结果表明:①1990年以来,东江流域土地利用变化的特点表现为城市化过程显著、非城镇用地结构变化明显,以及林地和灌草地大为减少的总体特征;②流域的上游、中游、下游三个区域在1990年-2000年和2000年-2009年两个时段,城镇用地增加量表现出相同的空间分异特征,而年增长率却表现出不同的空间分异特征,其中非城镇用地的转化在3个区域差异明显,自然植被退缩的程度表现为下游>上游>中游;③东江流域2000年-2009年时段的土地利用变化速度较之1990年-2000年时段整体上有所缓和,但在程度上仍具有区域差异性,显示出土地利用程度进一步向高度集约化发展;④人口增加、经济增长、区域发展政策的变化叠加在区域自然差异之上是东江流域土地利用变化及区域差异产生的主要原因。     

基于Fragstats的徐州市景观格局变化分析

选定徐州市中心城区作为研究区域,应用多时相Landsat TM／ETM＋遥感影像为数据源,利用支持向量机（SVM）分类器分别对1994、2000、2005年三个时相的遥感图像进行土地覆盖分类,并在Fragstats3．3景观格局软件平台上,基于景观尺度对徐州市景观格局进行全面的分析,分析结果表明：2005年徐州市景观整体较1994年具有更大的破碎度、更高的多样性和更低的聚集度,景观的类型与格局变化受到人为因素的影响较大;不透水面层逐渐取代耕地和城市绿地。     

Comparing PSO-based clustering over contextual vector embeddings to modern topic modeling

Efficient topic modeling is needed to support applications that aim at identifying main themes from a collection of documents. In the present paper, a reduced vector embedding representation and particle swarm optimization (PSO) are combined to develop a topic modeling strategy that is able to identify representative themes from a large collection of documents. Documents are encoded using a reduced, contextual vector embedding from a general-purpose pre-trained language model (sBERT). A modified PSO algorithm (pPSO) that tracks particle fitness on a dimension-by-dimension basis is then applied to these embeddings to create clusters of related documents. The proposed methodology is demonstrated on two datasets. The first dataset consists of posts from the online health forum r/Cancer and the second dataset is a standard benchmark for topic modeling which consists of a collection of messages posted to 20 different news groups. When compared to the state-of-the-art generative document models (i.e., ETM and NVDM), pPSO is able to produce interpretable clusters. The results indicate that pPSO is able to capture both common topics as well as emergent topics. Moreover, the topic coherence of pPSO is comparable to that of ETM and its topic diversity is comparable to NVDM. The assignment parity of pPSO on a document completion task exceeded 90% for the 20NewsGroups dataset. This rate drops to approximately 30% when pPSO is applied to the same Skip-Gram embedding derived from a limited, corpus-specific vocabulary which is used by ETM and NVDM.     

Landsat Yesterday and Today

Abstract

Since the late 1960s, the United States government has invested more than $1 billion in designing, launching, and operating the Landsat (land satellite) series of Earth-observing satellites. Global change researchers, geologists, and environmental scientists have used images gathered by the satellites for purposes ranging from human health research, energy exploration, and pollution detection to agricultural assessments, urban growth monitoring, and earthquake lineament studies.

The earliest data were captured on a digital medium called wide-band video tape (WBVT). However, two decades of unsound media storage conditions and a poorly maintained processing system have left the physically deteriorating WBVTs with no mechanism for interpretation. A national treasure was in jeopardy. With seed money from the National Aeronautics and Space Administration (NASA), the U.S. Geological Survey (USGS) began a project to rescue the data. More than 21,000 tapes from the 1970s have been transcribed to stable, archival media, preserving the data for future studies in Earth System Science.     

ETM+遥感影像铁化蚀变信息的提取方法

蚀变信息的研究一般利用ETM+遥感数据,通过数字图像来处理的.文中利用landsat7 ETM+卫星影像数据,采用主成分分析、比值法,对内蒙古巴彦淖尔地区进行铁化蚀变信息的提取.研究表明,由于受大面积第四系被氧化铁污染的影响.主成分分析提取铁的氧化物类蚀变异常的效果并不理想;而比值法抑制了大面积分布的第四系受氧化铁污染的影响.分析铁化蚀变异常显示效果较为理想,并结合一些遥感图像地质解译,更有利于应用遥感矿化蚀变异常划分找矿远景区.为进一步综合找矿预测提供了依据.     

基于Landsat ETM+影像的水体信息综合提取方法

以Landsat-7 ETM 影像为例,对比分析了常用的水体信息提取方法。针对已有方法无法准确提取河网支流和细小水体信息的缺点,提出了一种水体信息综合提取方法。方法利用谱间关系((TM2 TM3)-(TM4 TM5))和缨帽变换湿度分量TCW建立提取水体的最优空间掩膜,使用最大似然法去除最优空间掩膜中其他的地物信息。在浙江省绍兴及周边区域的实际工作中,本文方法较为完整地提取了研究区的水体信息,包括河网支流和细小水体。提取的相对精度优于其他方法。     

伊犁新垦区土壤盐碱化遥感信息的提取

土壤盐碱化是土地资源利用的主要障碍因子之一,利用遥感数据快速准确地提取盐碱地信息及其空间分布,可以为土地资源开发利用提供重要的科学依据,有着重要的现实意义。本文以新疆伊犁新垦区为研究区域,利用专家知识建立决策树,使用2008年8月的ETM数据,结合基础地理信息数据,提取不同程度的盐碱地信息。研究表明,利用基于知识的决策树方法,结合多源数据,能够有效提取盐碱地信息,并且分类结果准确,精度达到89.3% 。新垦区盐碱地占全区面积的10%,主要分布在伊犁河南岸大灌区,各级盐碱地比例为：重盐碱地占1%、中盐碱地占17%、轻盐碱地占82%。     

多源遥感图像分级校正研究

遥感图像在进行几何精校正时．需采用地面控制点(GCPs)，这些控制点一般来源于地形图．因此．校正后遥感图像的坐标和精度主要决定于地形图．本文以遥感图像作为校正空间．对研究区内Quick Bird、SPOT-5、ETM 和TM多源遥感图像采用分辨率由高至低分级校正．对分辨率最高的Quick Bird图像校正所需的地面控制点坐标采用静态GPS地面实测的方法．使校正后的图像具有较高精度．研究结果表明：用高精度的图像作为校正空间具有较好的校正效果．研究所涉及的4个时相、5种分辨率和4个遥感平台的多源遥感图像，分级校正后的精度均较高。