利用时空信息的单波段地表温度遥感反演

地表温度被认为是影响生态系统的关键因子之一,它与许多地表过程有关。目前,热红外卫星遥感技术是获取有关区域和全球尺度地表温度信息的一个有效、可行的手段。针对不同卫星上搭载的热红外传感器,许多学者开展了大量的研究,其中针对单波段热红外的特点(如Landsat TM/ETM+,CBERS和HJ-1B)提出了单通道(或单窗)算法。该类算法需要准确的地表比辐射率和大气参数(如大气水分含量)。这些参数在现实中又很难轻易获得,从而在一定程度上限制了现有算法的应用。针对HJ-1B高回访频率的特点,本文提出了利用多时相影像的时空信息来直接反演地表温度的Multi-Temporal and Spatial Information-Based Single Channel(MTSC),以解决现有算法对地表比辐射率和大气参数的过度依赖性。实例分析结果显示,基于MTSC法由HJ-1B反演得到的地表温度结果与MODIS地表(陆表和海表)温度产品具有很好的空间一致性;HJ-1B的陆表温度结果总体上被高估了约1 K,而海表温度结果总体上被高估了0.5 K;同时,MTSC法得到的HJ-1B地表温度结果具有更好的细节和空间完整性。最后,通过分析和讨论指出了一些可能的完善途径,如相似像元的确定、修改优化求解中的目标函数、参数的自适应初始化等,以便提高MTSC法的反演精度和实用性。     

Quantifying urban land cover change between 2001 and 2006 in the Gulf of Mexico region

We estimated urbanization rates (2001–2006) in the Gulf of Mexico region using the National Land Cover Database (NLCD) 2001 and 2006 impervious surface products. An improved method was used to update the NLCD impervious surface product in 2006 and associated land cover transition between 2001 and 2006. Our estimation reveals that impervious surface increased 416 km² with a growth rate of 5.8% between 2001 and 2006. Approximately 1110.1 km² of non-urban lands were converted into urban land, resulting in a 3.2% increase in the region. Hay/pasture, woody wetland, and evergreen forest represented the three most common land cover classes that transitioned to urban. Among these land cover transitions, more than 50% of the urbanization occurred within 50 km of the coast. Our analysis shows that the close-to-coast land cover transition trend, especially within 10 km off the coast, potentially imposes substantial long-term impacts on regional landscape and ecological conditions.     

Change detection of surface mining activity and reclamation based on a machine learning approach of multi-temporal Landsat TM imagery

Being able to quantify land cover changes due to mining and reclamation at a watershed scale is of critical importance in managing and assessing their potential impacts to the Earth system. In this study, a remote sensing-based methodology is proposed for quantifying the impact of surface mining activity and reclamation from a watershed to local scale. The method is based on a Support Vector Machines (SVMs) classifier combined with multi-temporal change detection of Landsat TM imagery. The performance of the technique was evaluated at selected open mining sites located in the island of Milos in Greece. Assessment of the mining impact in the studied areas was based on the confusion matrix statistics, supported by co-orbital QuickBird-2 very high spatial resolution imagery. Overall classification accuracy of the thematic land cover maps produced was reported over 90%. Our analysis showed expansion of mining activity throughout the whole 23-year study period, while the transition of mining areas to soil and vegetation was evident in varying rates. Our results evidenced the ability of the method under investigation in deriving highly and accurate land cover change maps, able to identify the mining areas as well as those in which excavation was replaced by natural vegetation. All in all, the proposed technique showed considerable promise towards the support of a sustainable environmental development and prudent resource management.     

Delineation of coalfield surface fires by thresholding Landsat TM-7 day-time image data

Surface fires are common in coalfields where coal is mined or exposed to sunlight for long durations of time. The heat energy emitted from these fires affects the signal recorded by sensors operating in the shortwave infrared regions of the electromagnetic spectrum. The Landsat TM/ETM+ band-7 is sensitive to solar reflected radiation as well as emitted radiation from a target. The ‘maximum solar reflection threshold’ method proposed in this study uses the highest spectral radiance that can be attributed to solar reflection as the conservative threshold to segregate the pixels with emitted component from those with reflected component of the EM energy. Investigations with Landsat TM/ETM+ data indicate a reflectance value of 0.23–0.25 as the most representative highest reflectance (threshold) in coal mining areas. The method apparently has the advantage that it is based on the reflectance characteristics of materials (sandstone-shale mixtures) typically found in coal mining areas.     

深化土地制度改革的广域视角和深度思维

在改革成为社会各界持续热议并正发力推进的今天,改革思维和视角的重塑与再造意义非凡。全球一体化的大势正推进着文化融合走向深入,洋为中用、中西合璧等观点正深度影响着我国改革进程,尤其是土地制度改革。笔者认为,只有立足文化基因的视角,明白"洋如何为洋用"才能做好"洋为中用",切实做到"大我"和"小我"的理性认知,公平和效率的均衡协调、底线和红线的表里融合理应成为我国土地制度改革的主论调和基本准则。     

3维最小二乘表面匹配泛型数学模型及在机载LiDAR条带平差中的应用

以3维表面间共轭点欧氏距离之和最小为理论基础,提出一种泛型3维表面匹配数学模型,并推导其最小二乘平差理论模型,利用该模型进行机载LiDAR点云条带平差。针对真实机载LiDAR点云数据进行条带平差对比实验,结果表明本文所提出的表面匹配模型,不仅能准确估计出相邻重叠3维表面间的正形变换参数,较好地解决机载LiDAR点云条带间配准问题,而且能同时适用于多种同名点对应准则,是一种泛型的配准模型。     

精密水准测量中重力改正的归算

传统水准测量是高精度水准测量的重要手段之一。文章基于DiNi电子水准仪测量数据,针对长距离、高精度水准测量高程的多值性,对水准面不平行改正和重力异常改正的原理进行详述。将其应用于某城市二等水准网平差计算中,证明了精密水准改正的有效性和必要性。     

地理国情普查地表覆盖与国情要素信息的提取方法探讨

地表覆盖分类和地理国情要素数据是地理国情普查成果数据的重要组成部分,同时也是统计分析的基本数据源。本文结合宁夏地理国情普查试点工作的技术和方法,详细阐述了普查试点生产过程中地表覆盖分类和地理国情要素信息的提取方法,并对生产技术方法进行了总结和探讨。     

Updating digital elevation models via change detection and fusion of human and remote sensor data in urban environments

OpenStreetMap (OSM) currently represents the most popular project of Volunteered Geographic Information (VGI): geodata are collected by common people and made available for public use. Airborne Laser Scanning (ALS) enables the acquisition of high-resolution digital elevation models that are used for many applications. This study combines the advantages of both ALS and OSM, offering a promising new approach that enhances data quality and allows change detection: the mainly up-to-date 2D data of OSM can be combined with the high-resolution – but rarely updated – elevation information provided by ALS. This case study investigates building objects of OSM and ALS data of the city of Bregenz, Austria. Data quality of OSM is discerned by the comparison of building footprints using different true positive definitions (e.g. overlapping area). High quality of OSM data is revealed, yet also limitations of each method with respect to heterogeneous regions and building outlines are identified. For the first time, an up-to-date Digital Surface Model (DSM) combining 2D OSM and ALS data is achieved. A multitude of applications such as flood simulations and solar potential assessments can directly benefit from this data combination, since their value and reliability strongly depend on an up-to-date DSM.     

基于移动GIS的土地执法动态巡查系统建设

目前土地执法巡查工作存在着作业方式落后、信息化程度低、巡查效率低和巡查人员不易监督的问题。针对这些问题,通过分析土地执法巡查的业务需求和移动GIS技术的特点提出构建基于移动GIS的土地执法动态巡查系统,在此基础上完成系统总体架构设计和功能设计,分析系统实现的移动GIS技术、数据库引擎技术、Web Services技术和基于时间维的GIS管理技术,重点阐述移动GIS技术在系统中的应用,最后完成系统开发。系统的使用改善了执法巡查现状,提高了巡查效率。