Mapping shoreline indicators on a sandy beach with supervised edge detection of soil moisture differences     

《International Journal of Applied Earth Observation and Geoinformation》2019

This study describes a method to map shoreline indicators on a sandy beach. The hypothesis is that, on this beach, spectral albedo is predominantly determined by moisture content and water lines can, therefore, be detected as albedo contrasts. A laboratory experiment is performed to relate moisture content to image albedo, and supervised edge detection is subsequently used to map the shoreline indicators with remote sensing imagery. The algorithm is tested with data from visible, near-infrared and shortwave-infrared wavelength regions. These results are compared to shoreline indicators obtained by a field survey and a shoreline indicator derived from a digital elevation model. Both the water line present when the imagery was acquired, as well as the maximum extent of the last flood, can be detected as a single edge. Older high water lines are confused with the last high water line and appear dispersed, as there are multiple debris lines present on the beach. The low water line, usually in saturated sand, also appears dispersed due to the presence of channels and troughs. Shorelines are constant moving boundaries, which is why shoreline indicators are used as a proxy. Unlike a mathematical indicator that is based on an elevation model, our method is more sensitive to the dynamic nature of shorelines. Supervised edge-detection is a technique for generating reproducible measurements of shoreline indicator positions over time, and aids in the monitoring of coastline migration.  相似文献   

Simulation of Kelvin wakes in optical images of rough sea surface     

《Applied Ocean Research》2019

Kelvin wake is one of the common wakes generated by moving ships and contains rich information about ships. In this paper, free wave elevations of Kelvin wake are calculated based on the Michell thin ship theory combined with a point source perturbation model. The probability density function of sea surface slopes is introduced to calculate the specular reflection of sunlight and skylight and the refraction of scattered light underwater. Satellite-detected Kelvin wakes are then simulated by adding surface specular reflectance and water-leaving reflectance. Simulation results agree well with satellite measurements. The specular reflection of sunlight is the decisive factor affecting the features of Kelvin wakes according to the simulation results. The main factors that influence the specular reflection of sunlight, such as the incident direction and observation direction, ship parameters, and background environment, are discussed. This study is helpful for wake detection and provides a preliminary theoretical method for the retrieval of ship information.  相似文献   

显著性权重RX高光谱异常点检测   总被引：1，自引：0，他引：1  

刘嘉诚  王爽  刘伟华  胡炳樑 《遥感学报》2019,23(3):418-430

高光谱图像异常点检测中,传统RX异常点检测算法忽略了空间相关性,背景估计不准确。本文提出了一种基于图像局部邻域光谱显著性分析的加权RX算法。该算法通过引入图像显著性分析,对基于概率密度为权重的图像背景建模进行改进,建立光谱显著性权重图,重新定义RX算法中的均值向量和协方差矩阵,并给不同的目标赋予不同的权值,达到优化背景估计的目的。利用合成高光谱数据和真实高光谱数据进行异常点检测实验,结果表明,对于同一组数据,本文算法检测到的异常点数比传统算法多,虚警率较低,有效地提高了检测率。  相似文献   

水产品中荧光假单胞菌(Pseudomonas fluorescens)RT-LAMP可视化检测方法的建立及应用     

魏梦泽  韩姣姣  芦晨阳  周君  陈炯  曲凌云  樊景凤  陈刚  苏秀榕 《海洋科学》2018,42(11):91-98

  相似文献   

多特征融合的高分辨率遥感影像飞机目标变化检测     

徐俊峰  张保明  余东行  林雨准  郭海涛 《遥感学报》2020,24(1):37-52

为利用高分辨率遥感影像实现高精度的飞机目标变化检测,提出了一种自适应的多特征融合变化检测与深度学习相结合的方法。首先,通过加权迭代的多元变化检测法获取变化强度图,并结合自适应的直方图统计法自动获取显著的变化与不变化样本;然后,提取多时相影像的光谱、边缘和纹理特征,完成多特征融合的变化检测,并通过形态学处理得到变化图斑;最后,利用训练的NIN(Network in Network)结构的卷积神经网络飞机识别模型,完成变化图斑的类型判别,实现变化飞机的检测。实验结果表明,本文方法在两组数据的正确率分别达到100%和91.89%,均优于对比方法,能实现准确可靠的飞机目标变化检测。  相似文献   

动态变化率与最大差值相结合的陆表生态变化检测     

李晓东  宋开山 《遥感学报》2021,25(6):1338-1350

为了实现更大尺度上的陆表生态变化检测,一种基于综合生态指数的动态变化检测方法用于不同时期卫星影像变化信息的提取。本文以东北地区的松嫩平原地表植被覆盖类型作为主要研究对象,2006年和2018年作为变化检测研究的标准年,陆地资源卫星影像数据作为实验数据源。动态变化的主要检测内容划分为年内变化和年际变化,最大差值算法计算影像数据的年内最大变化差异,同时动态比率算法计算年际动态变化。方法的实现过程如下,选择3个主要生态指数（水体指数、植被指数和土壤指数）用于计算年内最大差异和年际动态比率。然后,采用主成分分析法提取年内最大差异和年际动态比率的第一主成分,主要研究内容包括年内变化的显著性生态评价和年际变化方向、变换类型的分析与评价以及方法精度的验证。最终结果表明：（1）动态比率算法用于研究区年际变化检测,具有更高的变化检测精度,总体精度为93.80%,Kappa系数为0.876。（2）年内生态指数变化的最大差值用于定量衡量研究区年内变化检测。其中,第一主成分保留了83.04%的变化信息。同时,植被和水体对研究区的陆表生态变化有正方向的贡献。土壤裸露程度对陆表生态变化有负方向贡献。动态比率变化检测方法不需要设定适合的、动态的变化阈值,更便于大范围高效更新土地覆被类型。  相似文献   

基于孪生神经网络的土地利用现状年度变化检测   总被引：1，自引：0，他引：1  

张伟良  刘琦  吴长彬  杨光迪 《测绘通报》2021,(3):91-95,104

近年来,利用多期高分遥感影像,构建土地利用现状年度变化检测模型,并以此为基础支持土地利用现状年度变化检测的智能化发展,正是当前研究的难点所在。本文探讨了构建土地利用现状年度变化检测模型存在的问题。通过对土地资数据进行预处理,构建基于孪生神经网络的变化检测模型,以及对模型输出结果进行GIS优化获取目标区域的变化图斑,实现针对土地利用现状变化区域的快速提取。试验结果表明,该方法可快速发现不同时期影像中土地利用现状的变化位置,有效提升了土地利用现状年度变化检测的智能化水平,可服务于日常土地利用现状年度变更检查工作。  相似文献   

青海省地震灾后地物变化的快速识别     

韩建平 《测绘通报》2021,(11):120-123

地震灾后救援时间宝贵,有效利用灾后数据,快速对救援路线及居民情况进行准确的评估,能有效避免地震带来的进一步损害。地震并不是一次即停止,灾后余震同样威胁灾区群众的生命和财产安全。因此,根据灾区地质及居民分布制定后续可持续救援方案,也是灾后救援的重点,这不仅能使救援稳步进行,也可进一步规划安置居民。本文通过比较神经网络和传统机器学习方法,提出了自适应方法的地物分割算法,根据航拍影像的复杂程度使用神经网络和传统算法相结合的方式,通过比较识别出地物与原有测量数据的差别变化,判断灾后道路扭曲和地质变化,为救援工作提供准确的科学依据。  相似文献   

C波段调频连续波天气雷达探测系统及观测试验     

阮征  金龙  葛润生  李丰  吴俊 《气象学报》2015,73(3):577-592

对降水云更高时、空分辨率观测资料的需求推动了天气雷达技术的发展,调频连续波雷达(FMCW)系统采用收发分置双天线体制,采用数字直接移相(DDS)技术和快速傅里叶变换(FFT)信号处理技术,获取高度分辨率达到15、30 m,探测周期2—3 s的回波功率谱分布和谱参数,具有脉冲多普勒雷达无法比拟的探测优势。C波段FMCW(C-FMCW)雷达最小可测信号功率达到-170 dBm,微弱信号的定量标校是技术难点。采用标准信号源输出单频信号,经过数字直接移相扩展为与雷达系统相同扫频范围信号,得到最小输入功率可达-169.77 dBm的定标曲线,由定量标校后的谱分布计算得到回波强度谱密度分布。该雷达于2013年6月起在安徽定远开始观测,利用8月24日降水过程探测数据,与距离该地48 km的蚌埠和83 km的合肥SA扫描雷达观测数据,分别进行对流云与层状云的观测比对分析。对于均匀分布的层状降水云,C-FMCW雷达与SA雷达探测结果基本接近, C-FMCW雷达与蚌埠SA雷达的平均均方根误差为1.75 dB,与合肥SA雷达的平均均方根误差为2.02 dB,C-FMCW雷达与两部SA雷达探测的回波强度差异小于1 dB。对观测试验谱参数及回波强度谱密度分布进行了初步分析,C-FMCW雷达在研究降水云体的相态分区、晴空大气边界层回波等方面有较好的应用前景,有助于加深对强降水云中垂直运动的强烈变化的探测和认识。  相似文献   

Detecting climate change effects on forest ecosystems in Southwestern Romania using Landsat TM NDVI data   总被引：1，自引：0，他引：1  

Remus Pravalie  Igor Sîrodoev  Daniel Peptenatu 《地理学报(英文版)》2014,24(5):815-832

Nowadays, Southwestern Romania faces a large-scale aridization of the climate, revealed by the rise of temperatures and the decline of the amount of precipitations, with negative effects visible, among others, in the desiccation of forest vegetation. The present study means to identify the changes that occurred, quality-wise, in the past two decades （1990-2011） in forest vegetation in Southwestern Romania, and to establish the link between those changes and extant thermal stress in the region, whose particular features are high average annual and seasonal temperatures. In order to capture the evolution in time of cli- mate aridization, a first step consisted in using climate data, the temperature and precipitation parameters from three weather stations; these parameters were analyzed both individually and as aridity indexes （De Martonne and UNEP）. In order to quantify the changes in forest vegetation, NDVI indexes were used and analyzed, starting off from Landsat satellite images, acquired at three distinct moments in time, 1990, 2000 and 2011. In order to identify the link between the changes of NDVI index values and regional thermal stress, a yardstick of climate changes, statistical correlations were established between the peak values of average annual temperatures, represented in space, and negative changes in the NDVI index, as revealed by the change-detection analysis. The results obtained indicated there is an obvious （statistically significant） connection between thermal stress and the desiccation （degradation） of forest species in the analyzed area, with false acacia （Robinia Pseudoacacia） the main species to be impacted.  相似文献