Integrating spectral and non-spectral data to improve urban settlement mapping in a large Latin-American city     

Feilin Lai 《地理信息系统科学与遥感》2020,57(6):830-844

ABSTRACT

Information on urban settlements is crucial for sustainability planning and management. While remote sensing has been used to derive such information, its applicability can be compromised due to the complexity in the urban environment. In this study, we developed a remote sensing method to map land cover types in a large Latin-American city, which is well known for its mushrooming unplanned and informal settlements. After carefully considering the landscape complexity there, we designed a data fusion method combining multispectral imagery and non-spectral data for urban and land mapping. Specifically, we acquired a cloud-free Landsat-8 image and two non-spectral datasets, i.e., digital elevation models and road networks. Then, we implemented a set of experiments with different inputs to evaluate their merits in thematic mapping through a supervised protocol. We found that the map generated with the multispectral data alone had an overall accuracy of 73.3% but combining multispectral imagery and non-spectral data yielded a land cover map with 90.7% overall accuracy. Interestingly, the thermal infrared information helped substantially improve both the overall and categorical accuracies, particularly for the two urban classes. The two types of non-spectral data were critical in resolving several spectrally confused categories, thus considerably increasing the mapping accuracy. However, the panchromatic band with higher spatial resolution and its derived textural measurement only generated a marginal accuracy improvement. The novelties of our work are with the successful separation between the two major types of urban settlements in a complex environment using a carefully designed data fusion approach and the insight into the relative merits of the thermal infrared information and non-spectral data in helping resolve the issue of class ambiguity. These findings should be valuable in deriving accurate urban settlement information which can further advance the research on socio-ecological dynamics and urban sustainability.  相似文献   

Magnitude of latent heat in thermally loaded clays     

Sergio Samat  Laurent Brochard  Ioannis Stefanou 《国际地质力学数值与分析法杂志》2020,44(14):1926-1957

Temperature changes are known to induce specific couplings in clay, in particular, an anomalously high thermal pressurization in undrained conditions or a thermal compaction in drained conditions, both of which are potential threats for the mechanical stability and sealing capacity of the geomaterials. Thermodynamical analysis of those peculiar thermomechanical couplings points to a potentially important latent energy, which in turn could limit the temperature change upon heating or cooling. The direct measurement of latent energy developed during a laboratory geomechanical test is challenging. Instead, proper identification of thermal hardening in conventional experiments with temperature changes provides an alternative route to estimate latent energy. In this work, existing laboratory thermomechanical tests of clays are analyzed with a rigorous thermodynamic framework to quantify the magnitude of latent energy in thermomechanically loaded clays. A thermodynamically consistent constitutive model for fully saturated clays that combines two key features, (a) the temperature dependence of the blocked energy and (b) the framework of bounding plasticity, is proposed. The performance of the model is validated by reproducing results obtained in laboratory tests for Boom and Opalinus clays. The thermomechanical loads considered to validate the model performance were then used to estimate the percentage of work that remains latent in the clayey material during plastic yielding. We find that the magnitude of latent energy is quite significant, typically a few tens of percent of the total dissipated energy, and increases significantly with temperature. Accordingly, it is expected to play an important role in the thermomechanical response of clays.  相似文献   

Surficial fractures in the Navajo sandstone,south-western USA: the roles of thermal cycles,rainstorms, granular disintegration,and iterative cracking     

David B. Loope  Garrison R. Loope  Caroline M. Burberry  Clinton M. Rowe  Gerald C. Bryant 《地球表面变化过程与地形》2020,45(9):2063-2077

Deep (> 5 m) sheeting fractures in the Navajo sandstone are evident at numerous sites in southern Utah and derive from tectonic stresses. Strong diurnal thermal cycles are, however, the likely triggers for shallow (< 0.3 m) sheeting fractures. Data from subsurface thermal sensors reveal that large temperature differences between sensors at 2 and 15 cm depth on clear summer afternoons are as great as those that trigger sheeting fractures in exposed California granite. Extensive polygonal patterns in the Navajo sandstone are composed of surface-perpendicular fractures and were produced by contractile stresses. Numerous studies have shown that porewater diminishes the tensile strength of sandstone. Based on our thermal records, we propose that cooling during monsoonal rainstorms triggers polygonal fracturing of temporarily weakened rock. On steep outcrops, polygonal patterns are rectilinear and orthogonal, with T-vertices. Lower-angle slopes host hexagonal patterns (defined by the dominance of Y-vertices). Intermediate patterns with rectangles and hexagons of similar scale are common. We posit that outcropping fractures are advancing downward by iterative steps, and that hexagons on sandstone surfaces (like prismatic columns of basalt) have evolved from ancestral orthogonal polygons of similar scale. In lava flows, fractures elongate intermittently as they follow a steep thermal gradient (the source of stress) as it rapidly moves through the rock mass. In our model, a steep, surficial thermal gradient descends through unfractured sandstone, but at the slow pace of granular disintegration. Through time, as the friable rock on stable slopes erodes, iterative cracking advances into new space. Hexagonal patterns form as new fractures, imperfectly guided by the older ones, propagate in new directions, and vertices drift into a configuration that minimizes the ratio of fracture length to polygon area. © 2020 John Wiley & Sons, Ltd.  相似文献   

波段选择协同表达高光谱异常探测算法     

朱德辉  杜博  张良培 《遥感学报》2020,24(4):427-438

高光谱遥感影像具有光谱分辨率极高的特点,承载了大量可区分不同类型地物的诊断性光谱信息以及区分亚类相似地物之间细微差别的光谱信息,在目标探测领域具有独特的优势。与此同时,高光谱遥感影像也带来了数据维数高、邻近波段之间存在大量冗余信息的问题,高维度的数据结构往往使得高光谱影像异常目标类和背景类之间的可分性降低。为了缓解上述问题,本文提出了一种基于波段选择的协同表达高光谱异常探测算法。首先,使用最优聚类框架对高光谱波段进行选择,获得一组波段子集来表示原有的全部波段,使得高光谱影像异常目标类与背景类之间的可分性增强。然后使用协同表达对影像上的像元进行重建,由于异常目标类和背景类之间的可分性增强,对异常目标像元进行协同表达时将会得到更大的残差,异常目标像元的输出值增大,可以更好地实现异常目标和背景类的分离。本文使用了3组高光谱影像数据进行异常目标探测实验,实验结果表明,该方法与其他现有高光谱异常目标探测算法对比,曲线下面积AUC(Area Under Curve)值更高,可以更好地实现异常目标与背景分离,能够更有效地对高光谱影像进行异常目标探测。  相似文献   

地幔热导率的选取对动力学数值模拟的影响——以岩石圈张裂过程为例          下载免费PDF全文

谌永强  施小斌  廖杰  许鹤华  任自强 《地球物理学报》2020,63(5):1998-2012

目前存在有多种地幔热导率模型,不同模型在数值和随温压变化的特征上有明显的差异.为探究不同热导率模型对动力学数值模拟结果的影响,本文对不同模型下的岩石圈张裂过程进行模拟研究,探讨地幔热导率对岩石圈热传输、变形和熔融过程的影响及其作用机理.结果显示,不同热导率模型下,岩石圈的变形和熔融特征表现出明显差异.高热导率模型下,岩石圈破裂较晚,形成陆缘较为宽阔,地壳熔融强烈而地幔熔融较弱;低热导率模型下,岩石圈破裂较早,形成陆缘较为狭窄,地幔熔融强烈而地壳熔融较弱.这种差异源于不同地幔热导率下岩石圈和地幔热状态的变化及相应力学性质的改变.高热导率下,热传导的增温效应显著,岩石圈呈现较热的状态,其强度整体较低,壳幔耦合减弱;而低热导率下,热对流的增温效应显著,岩石圈呈较冷的状态,其强度整体较高,壳幔耦合增强.基于模拟结果,本文认为地幔热导率的选取对动力学模拟的结果有着较为显著的影响,相对于随温压的变化,热导率数值的差异对动力学数值模拟的结果影响更大,尤其是对于地幔熔融过程的影响.  相似文献   

2017年西藏米林6.9级地震前的热红外异常分析          下载免费PDF全文

张丽峰  王培玲  张朋涛  孙玺皓 《地震工程学报》2020,42(2):360-367

以小波变换和功率谱估计为研究方法,使用中国静止气象卫星热红外亮温数据,研究了2017年11月18日西藏米林MS6.9地震前的热辐射情况。结果发现震前4个月出现热红外异常,其后续演化方向与相关区域的断裂走向非常一致。在8月10日左右异常面积达最大,相对功率谱大于6倍的面积约为20万km^2,9月20日左右消失。分析相同频率2016年同期数据,结果显示在震中周围并未出现显著异常。时序曲线分析表明在8月12日相对功率谱达到峰值,为平均值的20倍,98天后米林地震发生;从7月4日到9月7日,地震当年相对功率谱偏离背景值和标准差,持续时间为65天。西藏地区的强震热红外异常表现出与地热资源分布较为一致的特征及特征周期相对较长的特点,为判定西藏地区的震情积累了一些经验。  相似文献   

FY-3D/MERSI-II全球火点监测产品及其应用   总被引：1，自引：0，他引：1  

郑伟  陈洁  闫华  刘诚  唐世浩 《遥感学报》2020,24(5):521-530

FY-3D/MERSI-II全球火点监测产品主要包括全球范围内的火点位置、亚像元火点面积和火点强度等信息,可用于实时监测全球范围的森林草原火灾、秸秆焚烧等生物质燃烧状况。火点判识算法主要根据中红外通道对高温热源的敏感特性,即含有火点的中红外通道像元辐亮度和亮温较远红外通道的辐亮度和亮温偏高,同时较周边非火点的中红外像元偏高,建立合适的阈值可探测含有火点的像元。亚像元火点面积估算主要使用中红外单通道估算,根据亚像元火点面积估算结果对火点强度进行分级,不同的级别表示不同程度的火点辐射强度。基于全球火点自动判识结果,每日生成0.01°分辨率的卫星遥感日全球火点产品,每月生产0.25°×0.25°格点的全球月火点密度图。在利用FY-3D/MERSI-II火点产品开展的全球火点监测应用中,对多起全球重大野火事件进行了监测,为防灾减灾、全球气候变化研究、生态环境保护等方面提供卫星遥感信息支持。  相似文献   

空-谱融合的条件随机场高光谱影像分类方法     

魏立飞  余铭  钟燕飞  袁自然  黄灿 《测绘学报》2020,49(3):343-354

高光谱遥感数据具有光谱信息丰富、图谱合一的特点,目前已经广泛地应用在对地观测中。传统的高光谱分类模型大多过分依赖影像光谱信息,没有充分利用空间特征信息,这使得分类精度还有很大的提升空间。条件随机场是一种概率模型,能够较好地融合空间上下文信息,在高光谱影像分类中已经得到越来越多的关注,但大部分条件随机场模型存在超平滑的现象,会导致影像细节丢失。针对该问题,本文提出了一种优化融合影像空-谱信息的高分辨率/高光谱影像分类方法,该方法将影像的纹理信息与原始光谱信息进行融合,利用SVM分类器对其进行预分类,并将各类概率定义为一元势函数,以融合空间特征信息;然后将空间平滑项和局部类别标签成本项加入二元势函数中,以考虑空间背景信息,并保留各类别中的详细信息。最后,通过两组的高分辨率/高光谱影像数据进行试验。结果表明,与SVM算法、传统的条件随机场方法和面向对象的分类方法相比,本文提出的算法在整体分类精度上分别提高了10%、9%和8%以上,同时在保持地物边缘完整性、避免“同谱异物”与“同物异谱”的现象方面有较明显的优势。  相似文献   

高强耐热铝合金钻杆材料优选          下载免费PDF全文

梁健  尹浩  孙建华  李亚红  王成彪  张金昌 《探矿工程》2020,47(4):65-71

铝合金钻杆的使用性能是制约深部钻探技术发展的“瓶颈”。本文综合考虑孔内工况因素和钻杆性能因素，以钻柱组合设计为基础准则，从特深孔钻探工程技术需求出发，开展了高强耐温铝合金钻杆材质选择和评价的试验研究。试验结果表明：2219铝合金固溶时效制度分别为535 ℃/1 h、165 ℃/20 h，2618铝合金固溶时效制度分别为530 ℃/1 h、200 ℃/20 h；2219铝合金在高温长时间暴露后的室温力学性能优于2618铝合金，在高温瞬时条件下的力学性能劣于2618铝合金；2219铝合金中含有Zr，该元素在热暴露过程中起到减缓溶质扩散速率的作用，这对提高热暴露后的剩余强度是有利的。  相似文献   

河北武城凸起地热田地热地质特征     

王迪  汪新伟  毛翔  武明辉  刘慧盈  张瑄  王婷灏 《地学前缘》2020,27(3):269-280

在“雄县模式”和环境压力的双重驱动下,河北地区已形成我国最大的地热供暖城市群。因此,研究武城凸起地热田地热地质特征,对河北省故城县地热开发具有重要的指导意义。本文通过测井、地震和区域地质资料,结合水化学特征、同位素测试结果的分析,系统分析了地热田的不同类型热储展布、储集层物性、地下热水补给来源和循环路径特征,并精细评价了地热资源量。结果表明武城凸起地热田热储类型主要为馆陶组砂岩热储和奥陶系岩溶热储。砂岩热储区域稳定分布,主要产水层为下馆陶组,底板埋深1 200~1 600 m,单井出水量79~123 m³/h, 井口水温52~54 ℃;岩溶热储有利区带主要分布在寒武—三叠系卷入的背斜核部,呈南北向带状展布,主要产水层为上马家沟组、下马家沟组和亮甲山组,顶板埋深2 100~2 900 m,单井出水量75~98 m³/h,井口水温82~85 ℃。地下热水来源为西部太行山脉和北部燕山山脉,热水沿着NE-SW向断裂破碎带和岩溶不整合面向上水平运移进入浅层热储,通过沧县隆起和邢衡隆起在武城凸起汇集,形成中低温地热田。地下热水质类型为Cl-Na型,最大循环深度为2 822.5~3 032.5 m,¹⁴C测年表明砂岩热储和岩溶热储年龄分别为21 ka和32 ka。明化镇组和石炭—二叠系分别为两套热储的直接盖层。武城凸起地热田地热资源量分层精细评价结果表明,热储地热资源量合计4.86×10¹⁰ GJ,折合标煤16.6×10⁸ t。年可开采地热资源量可满足供暖面积1.1×10⁸ m²,市场开发潜力巨大。  相似文献