在虚拟地景中进行线路初步设计的研究

LineBoss(线博士)系统是一种在传统的利用DTM进行线路初步设计的基础上,利用虚拟现实技术和计算机技术,建立虚拟地景环境并在其中进行线路初步设计的智能型系统。对其软件制作技术和系统特点进行了介绍。     

Detecting and Downscaling Wet Areas on Boreal Landscapes

This letter presents an approach to classify wet areas from European Remote Sensing 2 (ERS-2) synthetic aperture radar (SAR)-, Landsat Thematic Mapper (TM)-, and Light Detection and Ranging (LiDAR)-derived terrain data and downscale the result from the coarse resolution of satellite images to finer resolutions needed for land managers. Using discrete wavelet transform (DWT) and support vector machines (SVM), the algorithm finds multiple relationships between the radar, optical, and terrain data and wet areas at different spatial scales. Decomposing and reconstructing processes are performed using a 2-D DWT (2D-DWT) and inverse 2D-DWT respectively. The underlying relationships between radar, optical, and terrain data and wet areas are learned by training an SVM at the coarse resolution of the wet-area map. The SVM is then applied on the predictors at a finer resolution to produce wet-area detailing images, which are needed to reconstruct a finer resolution wet-area map. The algorithm is applied to a boreal landscape in northern Alberta, Canada, characterized by many wet-area features including ephemeral and permanent streams and wetlands.     

专业认证背景下的“计算机地图制图”课程教学改革

专业认证是教育部提升高校专业竞争力,满足社会需求的重要举措.专业认证对专业设置、课程改革提出了全新的理念和要求,已成为高校改革的原动力.基于专业认证背景,文中讨论“计算机地图制图”课程教学存在的问题,基于专业认证的现实需要,提出课程改革的方案,论述培养学生实践能力和创新能力方法.使“计算机地图制图”在工程文化教育中发挥重要作用.     

基于植被分布特征的森林景观建模方法

在虚拟地理环境中如何快速地生成具有特定空间格局的森林景观是一个具有挑战的问题。现有的研究主要以模拟或随机的方式确定树木的位置,但难以反映每个树种的分布特征。本文提出了一种基于图的中性景观模型,根据指定的景观指数生成特定组成结构和空间配置的森林景观。模型将格网随机划分为若干不规则的区域,并将其转化为对应的区域邻接图,通过源节点的受限生长生成特定大小和形状的图斑。相比其他中性景观模型,该模型在可控性和灵活性上具有优势,能对每种类型的景观特征分别进行表达。最后根据模型生成的森林景观确定树木的位置与种类。本方法不仅能为植被场景的可视化提供合理的植被分布,而且能反映森林景观的空间分布特征,为虚拟森林环境中的林业规划决策以及植被分布规律认知提供一定的支持。     

Impact of Gold Mining on Middle Siberian Taiga Landscapes from Landsat 7 Data

A Russian-American research team investigates the impacts of long-term intensive working of gold deposits on landscapes in the Middle Siberian taiga. These impacts include the displacement of bedrock and alluvial deposits, deforestation, and increasing fire incidence. Landsat 7 satellite imagery and field data were used in assessing the information yield of satellite scanner channels in the process of classification of the registered images. A schematic electronic map was constructed that shows zones of gold mining, predominant vegetation species, cutover and burned areas, and natural and artificial water bodies.     

3D visualisations in simulations of future land use: exploring the possibilities of new,standard visualisation tools

Abstract

Three-dimensional (3D) visualisations are an interesting method for representing model outcomes. Most visualisation techniques require expensive software and a lot of time to create them. When the visualisations need to be adapted frequently, a faster and more flexible method is needed. The first step of the proposed model is to create the 3D elements. These elements are combined with the base map, and distributed to the public using Google Earth. Both freely available and commercial software are used in this process.     

Modelling Flow Routing in Permafrost Landscapes with TWI: An Evaluation against Site‐Specific Wetness Measurements

In northern peatlands the thawing of permafrost increasing the active layer depth and changing the hydrology may lead to feedbacks in the climate system through changes in the biogeochemistry of carbon. We are examining this association on the Stordalen peatland complex in subarctic Sweden by analyzing a DEM derived from LiDAR‐data and the calculated TWI. The DEM, with a spatial resolution of 1 m, and the TWI are evaluated against two seasons of water level measurements from 30 sites in the peatland. The TWI is calculated with a form‐based flow routing algorithm which produces a natural flow routing pattern. In permafrost wetlands the topography is the major driver and is very important even though its magnitude is low. Site‐specific wetness (SSW) measurements from the sites were compared with the different peatland types that occur in the study area, i.e. fen, internal fen and palsa. The results showed a strong correlation between the TWI and the palsa. The TWI was better at describing general patterns than site‐specific hydrology. The evaluation of spatial patterns of TWI against SSW reveal the resolution required to develop the technique to be useful for climate change studies.     

广州市“数字绿化”仿真应用的城市园林景观3维可视化技术研究

广州市大力开展"数字绿化"管理平台建设,依托其中的广州市林业和园林局3维实景展示项目,以仿真应用为目的,研究基于CAD设计施工图和普查获取的城市园林景观GIS数据的3维可视化技术,具体叙述了相关的技术方法和流程。     

Examining the Effect of Ancillary and Derived Geographical Data on Improvement of Per-Pixel Classification Accuracy of Different Landscapes

Effective conservation and management of natural resources requires up-to-date information of the land cover (LC) types and their dynamics. Multi-resolution remote sensing (RS) data coupled with additional ancillary topographical layers (both remotely acquired or derived from ground measurements) with appropriate classification strategies would be more effective in capturing LC dynamics and changes associated with the natural resources. Ancillary information would make the decision boundaries between the LC classes more widely separable, enabling classification with higher accuracy compared to conventional methods of RS data classification. In this work, we ascertain the possibility of improvement in classification accuracy of RS data with the addition of ancillary and derived geographical layers such as vegetation indices, temperature, digital elevation model, aspect, slope and texture, implemented in three different terrains of varying topography—urbanised landscape (Greater Bangalore), forested landscape (Western Ghats) and rugged terrain (Western Himalaya). The study showed that use of additional spatial ancillary and derived information significantly improved the classification accuracy compared to the classification of only original spectral bands. The analysis revealed that in a highly urbanised area with less vegetation cover and contrasting features, inclusion of elevation and texture increased the overall accuracy of IKONOS data classification to 88.72% (3.5% improvement), and inclusion of temperature, NDVI, EVI, elevation, slope, aspect, Panchromatic band along with texture measures, significantly increased the overall accuracy of Landsat ETM+ data classification to 83.15% (7.6% improvement). In a forested landscape with moderate elevation, temperature was useful in improving the overall accuracy by 6.7 to 88.26%, and in a rugged terrain with temperate climate, temperature, EVI, elevation, slope, aspect and Panchromatic band significantly improved the classification accuracy to 89.97% (10.84% improvement) compared to the classification of only original spectral bands, suggesting selection of appropriate ancillary data depending on the terrain.     

基于伪卫星的改善GPS几何精度因子的研究

随着人们活动范围的日益扩大和周边环境的日益复杂,高精度GPS导航技术逐渐成为国内外研究的重点。GPS系统的定位精度在很大程度上取决于参与定位卫星的数目和几何布局,而几何精度因子(GDOP)正是衡量定位卫星几何布局优劣的量度。文章从几何精度因子着手,从理论上证明了伪卫星对GPS系统GDOP的改善,分析了伪卫星数量对GPS系统定位精度的影响。借助于仿真实验,结果表明,在GPS导航定位中,伪卫星能够显著增强卫星几何图形结构、提高测量精度、改善精度因子从而提高定位精度。     

地物光谱反射率野外测量实验方案改进

针对现有地物光谱反射率野外测量实验方案的不足,提出了地物光谱反射率的各向异性测量、不同环境条件的对比测量、不同时相的对比测量以及地物光谱反射率图像模拟四项实验改进方案。利用ISI921VF-128野外地物光谱辐射计和ArcG IS、ERDAS软件进行了实例测量与验证,揭示了真实地物光谱反射率的特征,模拟生成了"图谱合一"的地物光谱反射率图像,提高了实验教学质量。     

District-level mustard crop estimation for rajasthan: improving precision by in-season digital stratification

The acreage and yield of mustard crop in Rajasthan shows year to year variation. In the present study CAPE, analysis by incorporating digital stratification with current season data and comparison of coefficient variation (CV) at district level using conventional stratification with previous season data was undertaken. The stratification approach using current year’s data for mustard acreage estimation was adopted during 1994-95 and 1995-96 crop seasons and regional CV of less than 2 per cent was attained. A comparison of CV at district level for the years 1994-95 and 1995-96 with those obtained in previous two seasons (1992-93, 1993-94) indicated considerable improvement in precision (lower CV) is 7 out of 11 study districts. Mustard acreage estimate for Bharatpur (1995-96) had CV of 10.1 percent when conventional approach (past year data) for stratification was used. However, with the use of current year data for stratification CV reduced to 4.4 per cent The study suggests that use of in-season data for stratification improves precision for acreage estimation of crops like mustard which has high year to year variation in area.     

利用RFID技术进行项目现场测绘控制点的管理

在项目施工过程中测绘控制点管理非常重要,本文提出了基于RFID技术进行项目施工现场的测绘控制点的管理方式,完成了测绘控制点从纸质的手工管理到计算机自动化管理的转变,可以方便、快捷、准确地进行控制点的查找和现场定位以及点位的安全报警和重要点监控。     

一种提高大比例尺航测精度的方法试验研究

针对现有规范关于1∶500与1∶1000平坦地形测图必须采用全野外高程控制测量的规定,本文的试验采用装载组合宽角相机的无人飞艇低空航测系统,通过空中三角测量内业方法,突破了此技术限制。文中详述了三个试验测区的地理状况,以及采用的控制网布设方法,尤其是新设计的标志点之优点。成果表明,用航测内业加密方法所成图的高程和平面精度均超过现有规范标准。说明利用无人飞艇低空航测系统可以实现1∶500和1∶1000测图的全部航测任务,符合"允许采用新技术以更高质量的成果突破现有规范限制"的规定。     

Populating digital earth: improving access to Chinese remote sensing data for terrestrial applications

Global change has a significant impact on the lives of humankind. Earth observation can help to better understand our earth and cope with global change. With the availability of more reliable environmental data sets, digital earth is becoming a popular way to monitor the Earth and provide information to researchers and decision makers on environment protection, disaster mitigation, and social benefits. Therefore, accessing data with lowering costs is essential for digital earth. Nevertheless, there are big challenges in ensuring the feasibility of access to Chinese remote sensing data. This paper outlines some of the main challenges in realizing data sharing, provides an analysis of the core reasons leading to these challenges, and proposes recommendations to overcome the challenges. Amongst the main challenges are differences in data policy to gain access to satellite data, diverse data formats, and delivery mechanisms. The major challenge for the decision makers is to define a more open policy and for the scientist the challenge is to implement these polices for the benefit of all. This paper proposes that governments should adopt policies encouraging more open distribution and access to their data, in order to generate an improved digital earth with increased benefits to human society.     

基于混合像元灰度分布的提高点位平面精度方法

随着卫星遥感技术的日趋发展与成熟,利用卫星影像进行测绘生产也越来越重要。由于卫星影像与传统航空影像不同,当运用现有的测图相关技术手段将数字影像放大到像元级别以寻找控制点位时,受传感器随机分割生成的像元以及周围地物的影响,无法在一系列混合像元中准确进行控制点的定位和量测,增加了航测绘图产品的误差。为此,设计了一种用于数字摄影测量且不同于现有航测规范中所涉及的地面标志,并提出了基于该种标志的点位偏移量解算方法。该算法解决了在数字影像上寻找点位困难问题的同时提高了单点的定位精度。最后,通过Geo Eye-1卫星立体像对的定位实验验证了该方法的实用性和准确性。     

应用数值模型提高GPS可降水量反演精度的研究

利用建立在长江三角洲地区GPS观测网的资料,以上海宝山探空观测为例,进行了应用数值模式提高GPS可降水量反演精度的试验。研究结果表明:大气平均温度的估计误差直接影响大气可降水量的反演精度,用MM5中尺度数值预报模式预报估计的大气平均温度可减小大气平均温度的估计误差,从而提高大气可降水量的反演精度。