一种鲁棒的矢量地图数据的数字水印

数字水印是多媒体数据版权保护的一种有效方法。为了将水印技术应用于矢量地图数据的版权保护,根据矢量地图数据各要素层所合数据的多少,设计两种不同的数据分类规则,以实现嵌入不同大小的水印信息。通过仿真实验,可以看出算法具有很好的不可感知性和鲁棒性,尤其是抵抗矢量地图数据最常受到的对数据正常的增加、删除、修改、局部裁剪等更新操作。     

一种基于最小四叉树分块和特征夹角的零水印算法

为解决传统水印算法嵌入水印时对数据造成失真问题,本文提出一种基于最小四叉树分块和特征夹角的零水印算法。本算法以矢量地图数据线图元的特征点为基础,采用D-P压缩算法提取线图元的特征点,对矢量地图按照特征点坐标进行最小四叉树分块,保证每个分块内均可以构造一个完整的零水印信息,然后根据矢量地图坐标点之间在几何操作前后的不变性,利用每个最小分块内每一线图元上的前后特征点构造特征夹角,最后将置乱后的有效水印与特征夹角进行异或操作构造零水印信息。该算法保证了线图元的完整性,并且由于该算法不对原始数据进行任何修改,解决了传统水印算法的鲁棒性和不可感知性之间的矛盾。实验结果表明,该算法具有很好的鲁棒性,可以用来对矢量地图进行版权保护。     

基于调制方案的抗投影变换数字水印算法

针对传统数字水印算法无法抵抗投影变换攻击的问题,该文提出了一种对投影变换具有较高鲁棒性的数字水印算法。结合投影变换具有拓扑关系不变性以及在小范围内近似等特点,该文选择定位点和经纬线网格之间的包含关系作为水印载体,通过修改包含关系嵌入水印。实验证明该方法不仅对多种投影变换具有鲁棒性,而且能够抵抗裁剪、压缩等常见攻击,算法能够有效提高对矢量地图数据版权保护的能力。     

运用特征点的矢量空间数据盲水印算法

针对矢量空间数据水印攻击的特点,该文提出了基于特征点的矢量空间数据盲水印算法。在水印嵌入前,应用道格拉斯-普克方法,提取矢量数据特征点;对特征点进行离散傅里叶变换,将水印通过量化的方法嵌入离散傅里叶变换后的幅度系数和相位系数中;水印被多次嵌入,实现了水印的盲提取。试验结果表明,该方法引起的空间数据误差很小,同时对旋转、平移、要素排序、数据格式转换、裁剪、压缩、增删点等攻击具有较好的鲁棒性。     

一种面向地图对象的矢量地图数字水印方法

针对线状图层数据,面向地图对象,描述了一种能对2D矢量地图数据进行版权保护的水印算法。该算法把水印信息隐藏在地图对象的形状特征中,通过HASH排序和分组,把水印信息广泛地散布到图层中,并且实现了水印信息的盲检。实验表明,该算法具有很强的鲁棒性和实用性。     

基于空间特征的二维矢量地图可逆水印算法原理

可逆水印技术能够在精确提取水印信息的同时,完全无损恢复原始载体数据,更适用于矢量地图版权保护.提出一种基于空间特征的二维矢量地图可逆水印算法.该算法在保持矢量地图特征点相对位置的前提下,根据密钥对特征点位置进行非线性置乱,避免非授权用户对矢量地图高精度数据的使用,并在置乱后的特征,占'中嵌入水印信息,能够在提取水印信息的同时无损恢复原始矢量数据.实验结果表明该水印方案严格可逆,具有较好的隐蔽性.     

一种抗等角投影变换矢量地图数据水印机制

投影变换攻击是针对矢量地图数据水印的一种常见攻击方式,目前大多数水印算法都无法有效抵抗投影变换攻击。通过研究投影变换和矢量地图数据的特点,设计了一种折线变换方案,该方案是将折线由点坐标表示方式转化为距离和角度的表示方式,通过对转换后的角度系数嵌入水印,能够有效抵抗等角投影变换攻击。通过实验验证,该算法是可行的,且具有良好的不可见性和抗等角投影攻击的鲁棒性。     

矢量地图数据的数字水印技术

数字水印是通过向原始数据中嵌入标志版权信息的水印,在需要的时候可以把水印提取出来以证明版权归属,从而达到有效地保护版权的一种技术。结合矢量地图数据的特点提出一种矢量地图数据添加水印的算法,实验表明该算法具有较好的透明性和鲁棒性。     

矢量地图图幅裁剪技术研究

针对矢量地图的图幅裁剪要求,讨论了目前矢量地图图幅裁剪的原理和方法,并提出一种图幅裁剪的通用算法,适应于对矢量数据中的点、线和面数据的裁剪。实验表明,该算法运行快速,可靠性高。     

基于常函数的抗几何变换的矢量地理数据水印算法

基于常函数对于某些变换具有的不可变性,本文对抗几何变换的矢量地理数据水印算法进行研究。首先,对常函数的概念及其特征进行阐述,并推证了一个抗旋转、平移和放缩攻击的常函数;然后,基于建立的常函数,通过把水印信息嵌入到几何不变量中,提出了一种抗几何变换的矢量地理数据水印算法;最后,对提出的水印算法的鲁棒性进行了实验分析。实验结果表明,提出的算法能抵抗压缩、增点、删点、裁剪、平移、旋转、放缩以及由以上攻击组成的复合攻击,具有较好的鲁棒性。     

阿克苏河-塔里木河水系水质污染遥感监测与评价

 采用Landsat TM数据分析了阿克苏河—塔里木河断面水质污染状况,通过波段的DN值和常规监测数据建立能反映水质状况的 污染物监测模型。结果发现,将2000年常规监测数据代入模型后,与遥感数据的结果基本吻合| 重建阿克苏河—塔里木河的连续水体 污染变化曲线,得出污染物浓度随着远离上游而增加。     

Monitoring drought dynamics in the Aravalli region (India) using different indices based on ground and remote sensing data

The hard-rock hilly Aravalli terrain of Rajasthan province of India suffers with frequent drought due to poor and delayed monsoon, abnormally high summer-temperature and insufficient water resources. In the present study, detailed analysis of meteorological and hydrological data of the Aravalli region has been carried out for the years 1984–2003. Standardised Precipitation Index (SPI) has been used to quantify the precipitation deficit. Standardised Water-Level Index (SWI) has been developed to assess ground-water recharge-deficit. Vegetative drought indices like Vegetation Condition Index (VCI) and Temperature Condition Index (TCI) and Vegetation Health Index (VHI) have been computed using NDVI values obtained from Global Vegetation Index (GVI) and thermal channel data of NOAA AVHRR satellite. Detailed analyses of spatial and temporal drought dynamics during monsoon and non-monsoon seasons have been carried out through drought index maps generated in Geographic Information Systems (GIS) environment. Analysis and interpretation of these maps reveal that negative SPI anomalies not always correspond to drought. In the Aravalli region, aquifer-stress shifts its position time to time, and in certain pockets it is more frequent. In comparison to hydrological stress, vegetative stress in the Aravalli region is found to be slower to begin but quicker to withdraw.     

Landslide risk analysis between Giri and Tons Rivers in Himachal Himalaya (India)

The area around Sataun in the Sirmur district of Himachal Pradesh, India (falling between the rivers Giri and Tons; both tributaries of the Yamuna River) was studied for landslide vulnerability on behalf of the inhabitants. The study was made using extensive remote sensing data (satellite and airborne). It is well supported by field evidence, demographic and infrastructural details and aided by Geographic Information System (GIS) based techniques. Field observations testify that slope, aspect, geology, tectonic planes, drainage, and land use all influence landslides in the region. These parameters were taken into consideration using the statistical approach of landslide hazard zonation. Using the census data of 1991, vulnerability of the populace to the landslide hazard was accessed. As most of the infrastructure in the region is concentrated around population centres, population data alone was used for vulnerability studies.     

Gravity Changes Before Large Earthquakes in China: 1998-2005

Although it is well known that coseismic gravity changes take place during an earthquake, previous research has not yielded convincing evidence demonstrating that significant gravity changes occur before large earthquakes. Furthermore, even if we suspect that gravity changes occur before large earthquakes, we have yet to demonstrate how to consistently observe these changes for useful earthquake forecast that would bring benefits to society. We analyzed ground gravity survey data obtained in 1998, 2000, 200...     

GNSS系统及其技术的发展研究

阐述了国际上卫星导航系统的总体发展,对美、俄、欧、中的四大全球系统,以及相关的区域系统和增强系统进行了简单的介绍,研究分析了GNSS系统及其技术的发展趋势,同时分析了我国Compass全球系统面临的机遇和挑战,并提出了我国未来工作的建议.     

“4D”技术及其应用

介绍“４Ｄ”（即数字地面模型、数字正射影像、数字栅格地图和数字线划地图）系列产品的生产流程、关键技术、及其在耕地保护、防灾减灾救灾和城市规划等方面的应用方法。     

Virtual Australia: its key elements – know,think, communicate

Abstract

Virtual Australia is not a well-defined or agreed concept. This discussion paper conceptualises Virtual Australia as a ‘virtual [digital] model containing and representing all non-trivial objects and their contextual environment – from blue sky to bedrock – in real world Australia’. It describes a scenario for Virtual Australia, one or two decades from now, in which the locations and conditions of non-trivial objects and their environment are updated automatically through a combination of remote sensing and wireless communication technologies in support of a ‘Supranet’. It then examines the concept of the ‘Supranet’ – a pervasive information network based largely on wireless technology linking the physical world to a virtual model in real time – and develops and discusses three principal characteristics of the Supranet: the ability to have or collect specific information (know); the ability to process information (think); and the ability to communicate that information. If, in the near future, any or all non-trivial devices are to some extent able to know, think and communicate, the potential for object autonomy will be realised.     

Toward seamless indoor-outdoor applications: Developing stakeholder-oriented location-based services

Location-Based Services (LBS),an emerging new business based on smartphone and mobile networks,are becoming more and more popular.Most of these LBSs,however,only offer non-seamless indoor/outdoor applications and simple applications without giving stakeholders the chance to play an active role.Our specific aim is to solve these issues.This paper presents concepts to solve these issues by expanding the Open Location Services Interface Standard (OpenLS) to allow seamless indoor/outdoor positioning and to extend the content of the services to include information recommended by stakeholders.     

GIS空间数据的采集误差及其分析

本文详细阐述了GIS数据采集过程中的误差来源，重点分析了通过地图、遥感和摄影测量等方式采集数据所产生的误差及其特性，分析了其对GIS数据的影响与消减方法。     

地理数据库的关系模型及其实现

本文从以图论观点分析地理实体入手,系统阐述了地理数据库关系模型的设计法和过程。作者于1984年4～9月间在微型机上设计建立了关系型地理数据库的实方验系统(RGDB)。该系统采用了本文提出的关系模型,采用了可动态扩库的子库组合结构,这种结构具有灵活性和提高空间利用率的优点。RGDB含有多种功能的数据操作命令,除了具有一般检索功能外,还能进行“开窗”选取和十分“自由”的映象选取。本文对RGDB系统的主要性能和实现途径作了扼要介绍。