关联概率密度加权重力异常UKF滤波匹配导航算法

无味卡尔曼滤波(UKF)是一种通过采样来近似非线性分布,从而对非线性问题进行次优估计的滤波方法。利用实时观测得到的重力异常以及航行区域参考重力异常图,可以建立基于重力异常的UKF滤波匹配导航算法,以此校正惯性导航系统的漂移误差。针对选取与UT变换相同权系数来求取预测观测值而可能导致求得的预测观测值为伪观测值的问题,提出了利用关联概率密度函数对采样观测值进行加权的重力异常UKF滤波匹配导航算法。通过对某实验区域的实验进行计算分析,结果表明,基于关联概率密度加权重力异常UKF滤波算法能够克服传统加权预测观测值带来伪观测信息的问题,将惯性导航系统经纬向漂移误差降低至1.1 n mile以内,均优干传统加权算法和纯惯性导航系统的定位精度。     

基于小波的浙江省NDVI与自然—人文因子多尺度空间关联分析

对地表植被的空间分布格局及其与自然、人文因子间的关系开展综合的、多尺度的定量分析,这是全球气候变化背景下土地利用与覆被研究中的一项重要内容。以地处亚热带湿润季风区的浙江省为研究区,设置了东西向(样线A)和北南向(样线B)两条样线,并应用小波分析方法对研究区NDVI、高程、坡度和土地利用强度等因子的尺度特征以及这些因子间的多尺度相关关系进行了分析。结果表明:1研究区内,NDVI、高程、坡度及土地利用强度的空间分布格局存在四个尺度域;2上述因子在样线A及样线B上的空间分布分别存在两个主要特征尺度,其中东西向(样线A)上的特征尺度为40 km和80 km,北南向(样线B)上主要的特征尺度为30 km和50 km;3在较大尺度域(8 km以上),土地利用强度是影响NDVI空间分布的最主要因素,而在小尺度域(0~8 km),坡度和高程因子成为影响NDVI分布的主要因子。研究还认为,小波分析方法为识别地理要素空间分布的特征尺度、量测要素间任意尺度、任意位置上的相干关系,提供了方便的工具。     

河南省农作物虚拟水含量时空分异特征

在GIS技术的支持下,通过对1978—2013年河南省冬小麦、夏玉米、花生、棉花、油料作物、蔬菜6种主要农作物虚拟水量的计算与分析,探讨了其时空分异规律。河南省6种农作物单位质量虚拟水量在不断下降的趋势下有波动,2003年出现峰值,与当年大旱、所有农作物大面积减产有关;在农作物类型中,棉花单位质量虚拟水含量最高,多年平均值达到8 077.4 m3/t,蔬菜最低,多年平均值仅为159.95 m3/t。6种作物的虚拟水含量在空间分布上有明显差异,按其2013年的产量进行加权分析得到,第一等级区域为三门峡、郑州、信阳,第二等级为平顶山、洛阳、济源、开封,第三等级为南阳、驻马店、新乡、鹤壁、安阳、濮阳,第四等级为漯河,最低为许昌、周口、商丘、焦作。从整体看,西部、南部虚拟水含量高,而北部、东部虚拟水含量低。     

半干旱沙地-草甸区水面蒸发模拟及其影响因子辨识

在分析半干旱沙地—草甸区的水面蒸发过程及其影响因子的基础上,采用多元逐步回归分析方法,对水面蒸发的众多影响因子进行逐步筛选,找出显著影响因子,建立水面蒸发与其显著影响因子间的多元非线性回归模型,并模拟计算了彭曼蒸发公式、道尔顿水汽运输理论蒸发公式中的风函数,比较分析了彭曼模型、变异道尔顿模型、多元非线性回归模型计算的水面蒸发量。结果表明:彭曼模型、变异道尔顿模型和最终建立的多元非线性逐步回归模型所得结果十分接近,与实测水面蒸发量的趋势也很一致;除变异道尔顿模型稳定性稍差外,其余两者都具有较好的稳定性;多元非线性逐步回归方法可以找到水面蒸发的显著影响因子,剔除掉不显著影响因子,避免因子相关造成的影响,使所建回归模型具有良好的拟合效果,其决定系数达到了0.773,预测结果令人满意。     

气候变化背景下天山区域地表反照率特征分析

气候变化背景下地表反照率的变化能够深刻影响整个陆-气系统的能量收支平衡,引起区域以至全球的生态环境发生变化。基于2001-2013年16 d合成的MODIS/MCD43A3等数据,结合均值分析、斜率分析以及相关分析等研究方法,对气候变化背景下天山区域地表反照率时空变化特征进行分析。在空间分布上,近13 a来天山区域年均地表反照率达到0.217,伊犁河谷地区及天山北麓地表反照率较高,山区地表反照率较低,空间上呈交叉分布的特点;在时间分布上,研究区年均地表反照率缓慢增加,季节性差异明显,地表反照率秋季最高、春季最低,冬、春两季地表反照率波动强于其他季节;近13 a来地表反照率与气候因子之间存在较为明显的响应关系。年均地表反照率随着4、12月份气温的增加不断减小,随着7、8月份降水的减少而明显增加,与同期气温、滞后1月降水之间存在显著相关。     

基于区域多次回波点密度分析的城区LiDAR建筑物提取

以正确提取城区Li DAR点云中建筑物为目标,综合利用不同类别目标点云的回波特征以及地形信息,提出了一种基于区域多次回波密度分析的Li DAR点云建筑物提取方法。首先,将点云构建不规则三角网(triangulated irregular network,TIN),获取封闭的等高线;然后,利用等高线间的拓扑关系得到等高线族区域;最后,统计每一区域的多次回波点云密度信息,通过建筑物和树木区域多次回波点云在区域密度上的巨大差异来识别建筑物点云和树木点云。研究结果表明:该方法既充分利用了建筑物表面与植被间多次回波特性的差异,又不否定建筑物边缘同样存在多次回波的现象;通过封闭的等高线自适应地检测出地物目标的轮廓,弥补了传统Li DAR建筑物提取方法的不足;该方法能够较其他方法更准确地提取建筑物。     

基于遥感技术的近30年中亚地区主要湖泊变化

在全球气候变暖的背景下,研究中亚干旱半干旱地区主要湖泊的变化不仅对内陆水资源管理和可持续发展有着重要意义,也为进一步研究湖泊变化对气候变化和人类活动的响应提供基础。获取1978年MSS、1989年TM、1998年TM及2010年ETM的同季相4期遥感图像数据,通过人工解译提取中亚地区7个湖泊信息,获得近30 a的湖泊面积变化;利用T/P和Envisat雷达高度计提取1992—2012年的湖泊水位信息;基于湖泊面积和水位的时空变化特征分析了湖泊变化的影响因素。结果表明:近30 a来,由于湖泊类型的不同,除萨雷卡梅什湖外的其他6个湖泊均出现不同程度的面积缩减;其中,平原尾闾湖面积变化最显著,高山封闭湖相对平稳,吞吐湖泊的面积变化相对复杂;湖泊的水位变化模式因流域和湖泊类型而异;高山封闭湖泊受气候的影响较大,而吞吐湖泊受人为因素影响显著。     

核密度估计法支持下的网络空间POI点可视化与分析

城市空间POI点的分布模式、分布密度在基础设施规划、城市空间分析中具有重要意义,表达该特征的核密度法(kernel density estimation)由于顾及了地理学第一定律的区位影响,比其他密度表达方法(如样方密度、基于Voronoi图密度)占优。然而,传统的核密度计算方法往往基于二维延展的欧氏空间,忽略了城市网络空间中设施点的服务功能及相互联系发生于网络路径距离而非欧氏距离的事实。本研究针对该缺陷,给出了网络空间核密度计算模型,分析了核密度方法在置入网络结构中受多种约束条件的扩展模式,讨论了衰减阈值及高度极值对核密度特征表达的影响。通过实际多种POI点分布模式(随机型、稀疏型、区域密集型、线状密集型)下的核密度分析试验,讨论了POI基础设施在城市区域中的分布特征、影响因素、服务功能。     

Interplay between an axial channel belt,slope gullies and overbank deposition in the Puchkirchen Formation in the Molasse Basin,Austria

Deep‐water sediments in the Molasse Basin, Austria, were deposited in a narrow foreland basin dominated by a large channel belt located between the steep Alpine fold and thrust belt to the south and the gentler northern slope off the Bohemian Massif. Several gas fields occur outside the channel belt, along the outer bend of a large meander. Accumulation of these overbank sediments reflects a complicated interplay between slope accommodation and debris‐flow and turbidity‐flow interaction within the channel. The tectonically oversteepened northern slope of the basin (ca 2 to 3°) developed a regionally important erosional surface, the Northern Slope Unconformity, which can be traced seismically for >100 km in an east–west direction and >20 km from the channel to the north. The slope preserves numerous gullies sourced from the north that eroded into the channel belt. These gullies were ca 20 km long, <1 km wide and ca 200 m deep. As the channel aggraded, largely inactive and empty gullies served as entry points into the overbank area for turbidity currents within the axial channel. Subsequently, debris‐flow mounds, 7 km wide and >15 km long, plugged and forced the main channel to step abruptly ca 7 km to the south. This resulted in development of an abrupt turn in the channel pathway that propagated to the east and probably played a role in forming a sinuous channel later. As debris‐flow topography was healed, flows spread out onto narrow area between the main channel and northern slope forming a broad fine‐grained apron that serves as the main gas reservoir in this area. This model of the overbank splay formation and the resulting stratigraphic architecture within the confined basin could be applied in modern and ancient systems or for subsurface hydrocarbon reservoirs where three‐dimensional seismic‐reflection data is limited. This study elucidates the geomorphology of the oversteepened slope of the under‐riding plate and its effects on the sedimentation.     

Evaluating along‐strike variation using thin‐bedded facies analysis,Upper Cretaceous Ferron Notom Delta,Utah

Thin‐bedded delta‐front and prodelta facies of the Upper Cretaceous Ferron Notom Delta Complex near Hanksville in southern Utah, USA, show significant along‐strike facies variability. Primary initiation processes that form these thin beds include surge‐type turbidity currents, hyperpycnal flows and storm surges. The relative proportion of sedimentary structures generated by each of these depositional processes/events has been calculated from a series of measured sedimentological sections within a single parasequence (PS6–1) which is exposed continuously along depositional strike. For each measured section, sedimentological data including grain size, lithology, bedding thickness, sedimentary structures and ichnological suites have been documented. Parasequence 6–1 shows a strong along‐strike variation with a wave‐dominated environment in the north, passing abruptly into a fluvial‐dominated area, then to an environment with varying degrees of fluvial and wave influence southward, and back to a wave‐dominated environment further to the south‐east. The lateral facies variations integrated with palaeocurrent data indicate that parasequence 6–1 is deposited as a storm‐dominated symmetrical delta with a large river‐dominated bayhead system linked to an updip fluvial feeder valley. This article indicates that it is practical to quantify the relative importance of depositional processes and determine the along‐strike variation within an ancient delta system using thin‐bedded facies analysis. The wide range of vertical stratification and grading sequences present in these event beds also allows construction of conceptual models of deposition from turbidity currents (i.e. surge‐type turbidity currents and hyperpycnal flows) and storm surges, and shows that there are significant interactions and linkages of these often paired processes.