基于区域增长的海岸带黑暗像元自动提取算法研究

针对海岸带区域独特的地表状况设计了一个近海岸的黑暗像元自动提取算法。首先利用修订型归一化水体指数(RNDWI)和归一化植被指数(NDVI)对黑暗像元备选区域进行确定,然后从备选区域中找到初始黑暗像元,最后利用多阈值的区域增长法对黑暗像元的选取进行优化,最终计算得到黑暗像元值。应用此算法对Landsat-5 TM影像遥感数据进行处理,结果表明,大气校正之后的典型地物光谱曲线更接近于真实的光谱曲线,说明此算法设计合理,其大气校正结果与用ENVI软件进行FLAASH大气校正和黑暗像元法大气校正的结果相比,此算法更接近于FLAASH模型法,校正效果较好。同时利用黑暗像元自动提取算法得到大气校正后的结果大大减少了反射率值为负的情况,提高了数据的利用率。     

干旱区湖泊水体研究的最优遥感影像选择——以艾比湖为例

利用CBERS-2、Landsat-7 ETM+、ASTER遥感影像的光谱信息并结合实测光谱数据,获得艾比湖水体光谱特征.在对3种卫星影像进行几何校正、大气校正、图像镶嵌等预处理的基础上,提取各卫星影像上样点的各波段灰度值.然后对其求均值后生成反射折线图,通过与艾比湖水体光谱特征曲线进行对比,来选择最适合艾比湖水体研究的卫星影像.     

水体对城市区域热湿气候影响的建模及动态模拟研究

为了定量评估水体对城市区域热湿气候的影响,本文建立了水体一维热传输模型及水体与大气热湿交换简易动态模型,并通过现场实测验证了模型的合理性。将该计算模型与已有的城市区域热气候评价模型耦合,研究了以河流为代表的不同水体覆盖率条件下城市区域热湿气候的动态变化。研究表明随着水体覆盖率的增加,整个计算期间内白天大气温度平均下降了0.25℃,且白天气温降低的幅度要远大于夜间;选择合适的下垫面形式并合理增加城市水体覆盖率能有效改善城市热湿气候。     

拉布拉多海一年平整冰厚度SAR反演算法

在利用实测一年平整冰厚数据和同步全极化RADARSAT-2 SAR影像、全面分析不同SAR极化参数对海冰厚度敏感度的基础上,发现Alpha角最高;从理论上证实利用两者相关性反演冰厚的可行性,将所得经验方程用于冰厚反演,其结果与实测数据吻合较好;与现有常用方法的反演结果进行对比表明,新方法误差较小;Alpha角可以用于一年平整冰厚度反演,证明全极化SAR海冰信息反演冰厚确有优势。     

一种面向对象的武功湖水体信息自动提取方法

针对高分一号卫星遥感影像中水体信息自动提取问题,本文分别采用单波段阈值法、归一化差异水体指数法(NDWI)、基于像元和面向对象的组合分类方法对武功湖的水体信息进行提取,并对提取结果进行比较与精度评定。结果表明:不同的方法提取水体结果不同,精度亦不相同。其中,基于像元和面向对象的组合方法提取的水体信息最完整,精度可达91.52%;单波段阈值法精度最低,但结合NDWI法后提取水体精度明显得到改善,可以有效剔除建筑物和云层的阴影。此次试验为GF-1卫星遥感影像信息提取等工作提供一定科学参考。     

基于HJ-1B数据分形特征的水面面积提取方法研究

以巢湖为研究区域,提出了一种基于HJ-1B数据分形特征的水面面积提取方法。首先利用地毯法计算像元的分形信号,并对其进行特征分析;其次选用下分形第3尺度进行水面面积提取;最后利用同时期统计年鉴数据对提取结果进行精度评价。实验结果表明,该方法可以快速有效地提取水面面积,也为今后水体信息提取的相关研究提供了一种新的思路。     

基于TM影像的FLAASH模块大气纠正及评价

在高光谱遥感数据处理中,由于受到大气的影响,传感器接收到的辐射信息不能真实地反映地表反射光谱信息,因此对遥感影像进行大气纠正去除其影响,是高光谱遥感数据处理中极为重要的环节。文章介绍了FLAASH模块的基本原理和TM数据在进行大气纠正时的参数设置,并用FLAASH模块对豫西北区TM遥感影像进行大气校正以及对处理结果进行了薄云纠正程度,光谱纠正情况和归一化植被指数等的评价,并与ATCOR模型进行了对比。证明FLAASH模块大气纠正效果良好。     

南极冰川流速的遥感监测研究

利用卫星多时相、多波段影像测量法,对英格里特—克里斯泰森海岸不同时期的遥感影像进行几何纠正和配准及叠加处理,测量和计算出极记录冰川的平均流速,并对它们的变化特点进行了初步的分析和评价。     

遥感影像变化检测用于燃气管道安全隐患排查

基于深度学习进行遥感影像变化检测,对两幅不同时相的遥感影像进行校正、影像配准、生成变化检测图、隐患设施识别,最终计算燃气管道、输气站与隐患设施的隐患距离,判断隐患水平。分析基于遥感影像变化检测的燃气管道隐患排查流程。在隐患设施中(民房、围墙、铁塔、电杆、铁路、公路、厂矿企业等),除民房、围墙外,其他设施的修建需要有关部门的审批,因此安全隐患主要来自民房、围墙。     

基于RPC模型的QuicBird影像几何精校正的研究与探讨

QuickBird卫星是目前具有较高空间分辨率的商业卫星之一.由QuickBird卫星获取的原始遥感影像只进行了辐射校正和传感器校正,几何变形较大,无法满足用户的实际需求,需要作进一步的几何校正和正射纠正处理.RPC模型是通用传感器模型之一,可以用来模拟或替代严格成像模型,已广泛应用于影像的几何精校正和正射纠正过程当中...     

Validation of satellite data for quality assurance in lake monitoring applications

The operational application of remote sensing technologies to lake water quality monitoring requires products derived from remote sensing to be quantitatively self-consistent and have a certified accuracy. Fundamental elements in this quality assurance framework are sensor radiometric calibration and atmospheric correction models, which are briefly discussed in the paper. In order to evaluate the accuracy of present operational techniques to retrieve basic parameters from satellite data, such as water-leaving radiance and reflectance, an experiment was organised in the frame of SAtellite remote sensing for Lake MONitoring (SALMON), a European Union co-funded research project. A series of ship-based radiometric and atmospheric measuring campaigns were conducted on Lake Iseo and Lake Garda (Italy) together with limnological sampling. Four Landsat-5 Thematic Mapper (TM) scenes were acquired during different seasons and simultaneous in situ measurements were made. After the radiometric calibration procedure, satellite digital images were processed by applying two entirely image-based atmospheric correction models. These models account for the effects of both additive scattering and multiplicative transmittance effects in the atmosphere on the at-satellite measured signal. The results achieved using these procedures were evaluated by comparing satellite-based estimates with in situ measurements of water reflectance. The root mean square difference between Landsat TM-derived reflectance values and ground measurements was close to 0.010 reflectance for each TM spectral band. Such image-based correction models, requiring no in situ field measurements during the satellite overpass, constitute a valid method of lake water monitoring.     

Analysis on the feasibility of multi-source remote sensing observations for chl-a monitoring in Finnish lakes

Chlorophyll-a (chl-a) concentration of lake water can be measured with airborne (or spaceborne) optical remote sensing instruments. The rmse obtained here with empirical algorithms and 122 measurement points was 8.9 microg/l (all points used for training and testing). Airborne Imaging Spectrometer for Applications (AISA) was used in four lake water quality measurement campaigns (8 measurement days) in southern Finland during 1996-1998 with other airborne instruments and extensive in situ data collection. As empirical algorithms are employed for chl-a retrieval from remote sensing data, temporally varying factors such as surface reflection and atmospheric effects degrade the estimation accuracy. This paper analyzes the quantitative accuracy of empirical chl-a retrieval algorithms available as methods to correct temporal disturbances are either included or excluded. The aim is to evaluate the usability of empirical chl-a retrieval algorithms in cases when no concurrent reference in situ data are available. Four methods to reduce the effects of temporal variations are investigated. The methods are: (1) atmospheric correction; (2) synchronous radiometer data; (3) wind speed data; and (4) bidirectional scattering model based on wind speed and sun angle data. The effects of different correction methods are analyzed by using single-date test data and multi-date training data sets. The results show that the use of a bidirectional scattering model and atmospheric correction reduces the bias component of the measurement error. Radiometer data also appear to improve the accuracy. However, if concurrent in situ reference data are not available, the retrieval algorithms and correction methods should be improved for reducing the bias error.     

Estimation of chlorophyll-a concentration in turbid productive waters using airborne hyperspectral data

Algorithms based on red and near infra-red (NIR) reflectances measured using field spectrometers have been previously shown to yield accurate estimates of chlorophyll-a concentration in turbid productive waters, irrespective of variations in the bio-optical characteristics of water. The objective of this study was to investigate the performance of NIR-red models when applied to multi-temporal airborne reflectance data acquired by the hyperspectral sensor, Airborne Imaging Spectrometer for Applications (AISA), with non-uniform atmospheric effects across the dates of data acquisition. The results demonstrated the capability of the NIR-red models to capture the spatial distribution of chlorophyll-a in surface waters without the need for atmospheric correction. However, the variable atmospheric effects did affect the accuracy of chlorophyll-a retrieval. Two atmospheric correction procedures, namely, Fast Line-of-sight Atmospheric Adjustment of Spectral Hypercubes (FLAASH) and QUick Atmospheric Correction (QUAC), were applied to AISA data and their results were compared. QUAC produced a robust atmospheric correction, which led to NIR-red algorithms that were able to accurately estimate chlorophyll-a concentration, with a root mean square error of 5.54 mg m⁻³ for chlorophyll-a concentrations in the range 2.27-81.17 mg m⁻³.     

Numerical simulation of the wind field around different building arrangements

A numerical model with the RNG κ−ε turbulence closure model and a pressure correction algorithm of SIMPLEC is used to examine three different building configuration effects on wind flow. Comparisons of computational results with experimental data have been carried out for the vertical velocity profiles at some measurement points. For the experimental study, the building arrangements were presented by 1:150 scale models and tested in a low-speed wind tunnel. It was found that the wind environment for two improved arrangements with lower interval-to-height ratio is better than that for the reference layout with higher aspect ratio in terms of the natural ventilation. The interference effect is more obvious for two improved arrangements than the reference one. The numerical results also show that changing wind direction from perpendicular to the building facades to a 45°-incidence angle has significant effect on the flow field for different configurations.     

基于轨道移动激光扫描的圆形隧道正射影像纠正算法

高质量的隧道内壁影像是隧道病害检测的基础,而基于轨道移动激光扫描技术采集的圆形隧道内壁影像,在断面方向和运动方向上存在较大的影像长度误差。本文提出一种基于轨道移动激光扫描的圆形隧道正射影像纠正算法,利用速度纠正和正射投影纠正,插值激光扫描数据生成隧道内壁影像。经实验证明,该算法可有效纠正圆形隧道内壁影像在断面方向和运动方向上的长度误差,使影像具有较为精确的面积量测和病害信息判读功能。     

Water quality change in reservoirs of Shenzhen, China: detection using LANDSAT/TM data

The objective of this research is to explore a precise and fast way of monitoring water chemical and biochemical quality in the reservoirs of Shenzhen, China. Water quality change in 1988 and 1996 are detected by synthesizing satellite data and ground-based data. One scene Thematic Mapper (TM) image in winter of 1996 was acquired and the simultaneous in situ measurement, sampling and analysis were performed. Main methods include radiometric calibration of TM remote sensor, atmospheric correction to image data and statistical model construction. The results indicate that satellite-based estimates and in situ measured water reflectance have very high correlation, and the root mean square differences between two kinds of indices are close to 0.02-0.03 for each TM band in Visible-Near Infrared (VI-NIR) range. Statistical relationship between calibrated image data (average of 5 x 5 pixels) of TM bands and laboratory analyzed data of water samples indicated reflectance of TM band 1 to band 4 and organic pollution measurements such as TOC, BOD and COD had higher correlation. The same scene TM data in the winter of 1988 was processed in the same procedure. Results indicate that water quality of most reservoirs have become worse. Water of eastern reservoirs near Dongjiang River is characterized with higher TOC and TSS, and water of western reservoirs is characterized with higher BOD and COD.     

多工况的遗传算法校正管道摩阻系数

用遗传算法校正摩阻系数的过程中，由于测量数据的不足往往存在多解的情况，而瞬时分析方法又不适用于大型的管网。通过对真实管网的不同运行工况进行模拟并收集到大量的管网运行数据，在此基础上建立了不同工况的遗传算法摩阻系数校正模型，算例显示其计算结果与实测值较为接近。     

人工神经网络在油漆废水混凝氧化处理建模中的应用

利用改进的B－P算法，对油漆废水混凝氧化处理系统建立了人工神经网络模型，并利用该模型拟合、预测了一些实验数据。结果表明，模型的计算值与实测数据之间的误差很小，而且能正确反映各影响因素作用的内部机理。     

岩石变形破坏的数字散斑相关方法研究

 采用白光数字散斑相关方法作为实验的观察手段,对单轴压缩条件下岩石变形破坏进行实验研究。根据实验中数据采集方式的不同要求,将实验分成2组进行：一组是通过CCD相机记录岩石加载全程的试件表面散斑图像,进行岩石加载全程的变形演化实验研究,根据计算结果对岩石加载全程的变形演化和变形集中区域的位移演化进行研究;另一组是通过高速相机记录岩石破坏瞬态过程的试件表面散斑图像,进行岩石破坏瞬态过程的变形演化实验研究,采用不同时刻的散斑图像作为参考帧,分别进行塑性硬化到峰值阶段变形场演化特征、峰值到破坏阶段变形场演化特征的分析。同时,实验研究中还得到试件加载过程中局部化带内变形量值、带内变形最大值与最小值之比,带内最大值与带外平均值之比,以及试件表面裂纹扩展的平均速度等定量参数。     

沥青混合料压实状态的数字图像分析

探索了沥青混合料数字图像处理技术的可行性 ,并针对沥青混合料试件在不同压实成型方式下内部结构变化 ,利用CCD相机获取试件立断面的图像数字信息 ,采用压实评价参数---颗粒主轴方向 ,直观、快速、准确地进行数字图像分析 ,并与实际路面结构进行了对比。结果表明效果良好。