城区地表形变差分TomoSAR监测方法

压缩感知技术(CS)的差分TomoSAR技术解决了中高分辨率SAR数据在城区出现的叠掩问题,实现了城区地表形变信息的重构,但是该方法仅利用了目标的稀疏特性并没有考虑目标的结构特性,对具有这两种特性的目标进行重构时其性能较差。针对这一问题,本文采用联合Khatri-Rao子空间和块压缩感知(KRS-BCS),提出了一种差分SAR层析成像方法。该方法依据目标的结构特性和重构观测矩阵具有的Khatri-Rao积性质,将稀疏结构目标的差分TomoSAR问题转化为Khatri-Rao子空间下的BCS问题,然后对目标进行块稀疏的l1/l2范数最优化求解,最后通过理论分析和仿真试验对分辨能力和重构估计性能进行了定性和定量评价,仿真结果表明本文所采用的KRS-BCS方法不仅保持了高分辨率的优点,而且有效地降低了虚假目标出现的概率,大幅度提高了散射点准确重构概率,切实可行地解决了CS方法的不足。应用实例研究中,利用34景Envisat卫星ASAR时间序列影像对日本千叶县茂原市城区进行地表形变监测,并以一等水准点和实时测量的GPS站点观测数据作为参考形变结果进行验证,试验结果表明采用KRS-BCS方法反演的结果与参考形变结果保持了良好的一致性且形变速率整体偏差也较小,实现了较高精度的城区地表形变估计。

基于改进PSInSAR技术的非城区地表形变监测

为解决经典PSInSAR技术在非城区因受永久散射体空间分布不足而导致地形形变监测误差较大的问题,提出基于分时散射体(partial time scatterer,PTS)提取的改进算法。首先基于改进的经验模态分解对影像进行边缘保持平滑滤波降噪,然后采用可信概率估计对PTS目标进行联合提取,最后通过参数差分估计分离PTS相位和计算形变速率,从而得到监测区的地表形变。实验结果表明,提取的PTS目标基本可保持传统PS点的空间分布特性和时序变化趋势,提高非城区目标点的空间分布密度,本文算法具有有效性。

基于LiDAR点云的城区地表变化检测

随着摄影测量与遥感对地观测技术的快速发展,数据获取与生产越来越简单,快速准确的变化检测得到变化率和变化图斑,对于维护数据时效性有重要意义。本文通过实验总结出了一种采用两期机载LiDAR点云数据,快速检测城区地表变化的技术方法:首先对机载LiDAR点云进行坐标转换配准等数据预处理后,先将数据分类,然后利用分层聚类差值法进行变化检测得到变化区域,最后对变化结果进行分析。经实践证明该方法变化检测准确率达到83%,节约了38%的人工工作量,是一种有效的城区地表变化检测方法。

高光谱-LiDAR多级融合城区地表覆盖分类

城市地区地表覆盖分类在城市研究中是一个十分重要的方向。遥感作为获取地物物理属性的一种重要技术手段,已初步应用于分类研究中。然而,随着城镇化的不断推进,城市内部地物类型越来越复杂,单一的遥感影像已无法满足城区地表覆盖分类中高精度的要求。高光谱影像和LiDAR数据能够分别表征地物的光谱信息及高程而被广泛应用。因此,根据两者之间互补的优势,本文提出了基于高光谱影像和LiDAR数据多级融合的城区地表覆盖分类方法。首先对两幅影像分别进行特征提取,将提取到的光谱、空间及高程信息进行层叠实现特征级融合。对得到的特征影像的所有像素点进行分类,然后利用LiDAR点云数据提取的建筑物掩膜,对非建筑物部分进行分类,再次实现特征级融合,以此改善建筑物区域与非建筑物区域的混淆。然后将未使用掩膜得到的分类结果与利用掩膜得到的分类结果进行投票实现决策级融合。最后利用条件随机场模型对分类结果进行后处理操作,达到平滑图像去除噪声点的目的。

基于分时散射目标的非城区地形PS-InSAR监测

永久散射体(PS)在非城区的分布密度通常难以满足PS-InSAR技术的地形监测需求,导致PS-InSAR监测误差较大,而非城区通常存在一定时段内的散射目标,即分时散射目标,为此,本文提出基于分时散射目标的改进PS-InSAR算法。首先采用通过边缘保持EMD算法对SAR影像干涉对进行降噪;然后以双层K-means聚类提取非城区的分时散射目标候选集,并通过可信概率提取可靠的分时散射目标;最后通过组内加权参数迭代和组间等权融合,计算监测区的地表形变。试验结果表明,提取的分时散射目标与同位置PS点具有相近的分布特性和变化趋势,较大地提高了非城区目标点的分布密度,提高了非城区地表形变监测的精度。

济南市不同下垫面降雨径流水质变化特征分析

分析济南市城区在降雨时期不同下垫面径流的污染物含量变化过程,可以为更加合理的利用雨水资源,减轻水资源供需矛盾给城市建设带来的压力提供理论依据。在对居民区屋面径流、居民区道路径流、高架桥雨水径流、河道采用水质单因子评价法分析各下垫面径流污染物浓度变化的前提下,采用综合水质标识指数评价法进一步实施水质评价,分析地表径流水质在降雨时期的时空变化规律。结果表明:屋面径流及居民区道路径流的降雨初期污染最为严重,且初期冲刷作用明显,降雨后期径流水质较好;高架桥路面径流污染相对较轻,河道水质较差,局部河段严重超过城区径流水质Ⅳ类水标准,不可直接利用。

Distribution of heavy metals in the topsoil of the Jining mining area

The geochemical baseline is the fundamental reference for environmental change and assessment.In this article we describe cluster and regression analyses with a normalization procedure.The elements Sc and Ag were chosen to calculate the environmental geochemical baseline.The geoaccumulation index was calculated and mapped to indicate the environmental quality of the soil.The results show that the urban areas are barely polluted with Ni and Cr but the rural areas in the southern part of the city, and the western part of the lake,are polluted with Ni,Cr,and Cu at the second level.On the other hand,the rural areas in the southern part of the city,and the western part of the lake,are polluted with As at a moderate level.The other area is polluted at the second level.An increase in As pollution occurs in a direction from northeast to southwest.The Cd pollution follows a trend similar to As,with an additional smaller contaminated area polluted at levelⅢ.The Hg pollution typical of urban areas occurs in the main and northern parts of the city.The geochemical accumulation index decreases from the city center to the periphery.The highest pollution level reaches levelⅣ,which indicates that the soil is seriously polluted with Hg.The southern part of the city and the rural areas to the west of the lake are not contaminated with Hg.Geological factors and the disturbance from human activities are both possible major factors:further research is needed to identify them.

Geostatistical Assessment of Pb,Zn and Cd Contamination in Near-Surface Soils of the Urban-Mining Transitional Region of Isfahan,Iran

Due to the lack of regulation and environmental education and awareness, Sepahanshahr located in vicinity of Isfahan City, central Iran, is now a rapid growing residential area suffering from the considerable consequences of poorly regulated mining activities operating in its vicinity. A survey was carried out on soil Pb, Zn and Cd concentrations around Sepahanshahr Town to explore the spatial structure of Pb, Zn and Cd distribution and to map their concentrations using geostatistical techniques. 100 near-surface soil samples were collected and analyzed for Pb, Zn and Cd and some related soil physical and chemical variables such as pH, organic matter content, electrical conductivity, and clay, silt and sand contents. The variography results showed a strong spatial dependency in heavy metals concentration due to the dilution effects of natural factors including atmospheric dispersion and precipitation. The almost same range values calculated for both In-transformed Pb and sand data suggested presence of spatial co-regionalization. However, In-transformed Zn data showed a shorter spatial dependency among the three tested heavy metals. Kriged maps of all three heavy metals showed a strong gradient of contamination around the three mining sites activating in the area. The results of this study provide insight into identification of the extent and spatial variability of Pb, Zn and Cd pollution in the mining sites and surrounding urban areas.

Remote sensing-based artificial surface cover classification in Asia and spatial pattern analysis

Artificial surfaces, characterized with intensive land-use changes and complex landscape structures, are important indicators of human impacts on terrestrial ecosystems. Without high-resolution land-cover data at continental scale, it is hard to evaluate the impacts of urbanization on regional climate, ecosystem processes and global environment. This study constructed a hierarchical classification system for artificial surfaces, promoted a remote sensing method to retrieve subpixel components of artificial surfaces from 30-m resolution satellite imageries(Globe Land30) and developed a series of data products of high-precision urban built-up areas including impervious surface and vegetation cover in Asia in 2010. Our assessment, based on multisource data and expert knowledge, showed that the overall accuracy of classification was 90.79%. The mean relative error for the impervious surface components of cities was 0.87. The local error of the extracted information was closely related to the heterogeneity of urban buildings and vegetation in different climate zones. According to our results, the urban built-up area was 18.18×104 km2, accounting for 0.59% of the total land surface areas in Asia; urban impervious surfaces were 11.65×104 km2, accounting for 64.09% of the total urban built-up area in Asia. Vegetation and bare soils accounted for 34.56% of the urban built-up areas. There were three gradients: a concentrated distribution, a scattered distribution and an indeterminate distribution from east to west in terms of spatial pattern of urban impervious surfaces. China, India and Japan ranked as the top three countries with the largest impervious surface areas, which respectively accounted for 32.77%, 16.10% and 11.93% of the urban impervious surface area of Asia. We found the proportions of impervious surface and vegetation cover within urban built-up areas were closely related to the economic development degree of the country and regional climate environment. Built-up areas in developed countries had relatively low impervious surface and high public green vegetation cover, with 50–60% urban impervious surfaces in Japan, South Korea and Singapore. In comparison, the proportion of urban impervious surfaces in developing countries is approaching or exceeding 80% in Asia. In general, the composition and spatial patterns of built-up areas reflected population aggregation and economic development level as well as their impacts on the health of the environment in the sub-watershed.

Evapotranspiration estimation considering anthropogenic heat based on remote sensing in urban area

Urbanization influences hydrologic cycle significantly on local,regional even global scale.With urbanization the water resources demand for dense population sharpened,thus it is a great challenge to ensure water supply for some metropolises such as Beijing.Urban area is traditionally considered as the area with lower evapotranspiration(ET) on account of the impervious surface and the lower wind speed.For most remote sensing models,the ET,defined as latent heat in energy budget,is estimated as the difference between net radiation and sensible heat.The sensible heat is generally higher in urban area due to the high surface temperature caused by heat island,therefore the latent heat(i.e.the ET) in urban area is lower than that in other region.We estimated water consumption from 2003 to 2012 in Beijing based on water balance method and found that the annual mean ET in urban area was about 654 mm.However,using Surface Energy Balance System(SEBS) model,the annual mean ET in urban area was only 348 mm.We attributed this inconsistence to the impact of anthropogenic heat and quantified this impact on the basis of the night-light maps.Therefore,a new model SEBS-Urban,coupling SEBS model and anthropogenic heat was developed to estimate the ET in urban area.The ET in urban area of Beijing estimated by SEBS-Urban showed a good agreement with the ET from water balance method.The findings from this study highlighted that anthropogenic heat should be included in the surface energy budget for a highly urbanized area.