共查询到18条相似文献，搜索用时 93 毫秒
1.
杭州湾HJ CCD影像悬浮泥沙遥感定量反演 总被引：6，自引：0，他引：6
利用环境小卫星CCD(HJ CCD)影像对杭州湾悬浮泥沙浓度(SSC)进行了反演研究。通过对杭州湾水体遥感反射率(Rrs)与SSC进行相关性分析发现,在690nm和830nm左右出现显著的反射峰,分别位于HJ CCD影像的第3和第4波段范围内;大于700nm波长处的Rrs与SSC相关性较好。基于实测Rrs和SSC之间的相关关系,利用第4和第3波段比值作为遥感因子建立SSC反演模型,模型决定系数达到0.90。借鉴近红外-短波红外(NIR-SWIR)结合的大气校正方法反演出的准同步MODIS气溶胶数据,实现了HJ CCD影像的大气校正,第3、第4波段的大气校正结果相对误差分别为5.54%和6.97%。结果显示,HJ CCD影像反演的SSC相对误差为7.12%;杭州湾悬浮泥沙浓度要显著高于长江口,且内部差异明显。研究表明,通过适当的大气校正方法和反演算法,HJ CCD影像可用于杭州湾悬浮泥沙浓度的估计。 相似文献
2.
悬浮泥沙的粒径分布特征不仅体现了悬浮颗粒态物质的存在状态,而且可以指示水动力及再悬浮作用的过程和强度,因此研究悬浮泥沙粒径分布特征具有重要意义。利用Mie理论建立悬浮泥沙平均粒径反演模型,结果表明,悬浮泥沙后向散射系数与其平均粒径的三次方线性关系明显,4个波段(412nm、443nm、555nm、667nm)拟合方程决定系数均在0.93以上,拟合误差最小值为16.6322%(412nm),最大值为20.3143%(667nm)。利用QAA算法从MODIS影像上反演研究区域悬浮泥沙后向散射系数,并结合反演的悬浮泥沙浓度推算研究区域表层悬浮泥沙的平均粒径。对比发现,近岸高悬浮泥沙区域的反演结果与实测数据吻合较好,相关研究可以为深入开展陆海相互作用、海洋生态系统演变和海洋参与全球碳循环等研究提供重要数据支持。 相似文献
3.
本文根据1984年的NOAA卫星多时相遥感资料,对杭州湾及其周围海区的表层悬浮泥沙浓度分布特征、扩散范围及季节性变化等作了分析与研究。并对悬浮泥沙影响建港工程及海区自然环境净化等问题进行了讨论。 相似文献
4.
HJ-1A/B卫星CCD影像的武汉市东湖水色三要素遥感研究 总被引：2，自引：0，他引：2
以武汉市东湖为研究区域,利用同步的MODIS-Terra气溶胶光学厚度数据为输入参数,采用FLAASH模型对2010年3月11日HJ-1A/B卫星CCD影像进行大气校正处理,并利用多年实测数据建立叶绿素a浓度、悬浮泥沙浓度、黄色物质吸收系数三要素神经网络反演模型,对水色三要素进行反演。通过对反演结果与实测数据的对比分析可知,悬浮泥沙浓度、黄色物质吸收系数和叶绿素a浓度的平均相对误差分别为28.052%、17.628%和35.621%,表明HJ-1A/B卫星CCD传感器基本能满足II类水体水色要素的遥感监测需求。 相似文献
5.
辐射沙脊群海域悬沙场遥感反演方法 总被引：1，自引：1，他引：0
利用2006年江苏908调查水文泥沙测验数据和同期MODIS影像建立遥感定量反演模式,获取了半个潮周期的悬沙场以及全潮平均悬沙场,进行了辐射沙脊群海域悬沙场遥感反演方法的研究,并结合悬沙数学模型对结果进行了验证。研究表明,在辐射沙脊群海域,敏感参数(B1-B4)/(B1+B4)的对数模式反演悬沙场精度较高;遥感反演结果在总体上与数学模型计算结果相似,悬沙高值区主要分布在弶港、废黄河口和长江口附近;在细节上比数学模型表现得更精细,能清晰地反映河口、沙洲、水道等地貌对悬沙分布的影响。 相似文献
6.
1975年—2018年白洋淀湿地变化分析 总被引：2，自引：0，他引：2
白洋淀湿地生态功能重要、战略地位特殊，研究其时空变化规律具有重要意义。本文基于1975年—2018年间10期Landsat卫星遥感影像，辅以2017年—2018年高分二号（GF-2）卫星遥感影像，在野外考察湿地类型及其覆被特征基础上，人机交互解译获取各期土地利用/覆被分类图，从面积变化、类型转化、景观格局变化方面分析了近43年白洋淀湿地变化时空特征，讨论了影响分析结果的不确定性因素以及湿地变化成因。结果表明：1975年—2018年白洋淀湿地面积总体呈减少趋势，净变化-68.20 km2（-24.83%）。其中，1975年—1990年湿地面积波动性小、基本稳定，1990年—2011年湿地面积持续性减少，2011年—2018年湿地面积呈现增加趋势。湿地与非湿地类型相互转换区域主要分布于淀区南部、西部、北部的水体—水生植物—耕地—建设用地过渡区域。近43年白洋淀湿地景观趋于破碎、复杂和异质。遥感影像选取月份、年份，以及土地利用/覆被分类体系、分类方法，是影响分析结果的主要不确定性因素。气候、水文等自然因素变化，叠加工农业及城镇生活用水、上游水利工程蓄水、地下水开采等人为因素变化，是白洋淀湿地面积减少、趋于干化的成因。 相似文献
7.
毛乌素沙地东南缘NDVI植被变化特征分析 总被引：2，自引：0，他引：2
《地理空间信息》2020,(5)
以毛乌素沙地东南缘5个区县为研究区,采用2003年、2007年、2011年和2015年的MODIS NDVI数据,利用最大值合成和趋势分析等方法分析了研究区季相、生长季和年际轻度NDVI空间变化情况,得到毛乌素沙地东南缘植被的时空演变特征。结果表明:①从NDVI季相的年际变化来看,毛乌素沙地植被在春季呈轻度退化趋势,在夏季呈轻度改善趋势,秋季和冬季基本不变,其中东南部植被增加大于西北部,夏季植被增加最明显;②植被生长季的年际变化特征与夏季相似,改善土地主要分布于神木市和榆阳区,其他地区分布较零散;③从2003-2015年NDVI年际变化来看,基本不变等级面积占比为33.61%,植被处于轻度退化等级的面积占比为46.74%,轻度改善等级的面积占比为15.51%。总体而言,2003-2015年毛乌素沙地东南缘植被整体呈微弱恢复态势,反映该区域的生态建设具有一定效果。 相似文献
8.
为更好地研究河流污染、河道阻塞、土壤沙化和湖泊面积锐减等问题,本文采用适宜的分析模型和高分辨率资源一号卫星影像,按照影像预处理、影像分类、矢量提取、特征分析的作业步骤,利用面向对象的遥感影像分类方法进行信息提取,针对夏冬两季的地物特征分别对鄱阳湖地区进行沉积物识别、地物类别判读以及湖泊的面积变化分析。研究表明:夏季鄱阳湖区域水体面积较大,泥沙较少,而冬季湖泊面积减少,泥沙等沉积物增多,并且存在相互影响的关系。 相似文献
9.
黄河口水体光谱特性及悬沙浓度遥感估测 总被引：10，自引：1，他引：10
通过黄河口含沙水体野外遥感光谱反射率的观测实验，探讨了黄河口水体表观光谱特性，分析了悬浮体中有机颗粒含量和悬沙粒度对光谱特性的影响。针对Landsat TM／ETM^＋影像波段特性，对黄河口含沙水体在其可见光至近红外4个波段的光谱特性进行了模拟分析，并结合表观光谱观测数据建立了经验回归函数，以估测不同时相黄河口水体表层悬沙的浓度。 相似文献
10.
本文利用Sentinel-1数据获得了2016-2020年月度长江干流上海-宜宾段水域面积,并分析其年际、年内变化规律。分析结果表明,①月度变化规律为1-5月水面面积变化相对平稳,6-8月水域面积逐步增加,在7月达到峰值;9月稍有回落,10月再次达到峰值后逐步减少至稳定。②季节性变化规律为冬季水域面积最小,夏季水域面积最大,夏季和冬季呈现明显的季节差异。③年际变化规律为2016年后水域面积呈增长趋势,其中2017-2019年水域面积相对稳定且缓慢增长,2020年面积急剧增长。分段而言,水域面积随时间的变化幅度为下游>中游>上游,中上游变化相对平稳,下游较显著。④易发生洪涝的断面主要分布在中下游段,需引起重视并做好监测预警。 相似文献
11.
12.
Yuandong Wang Xiyong Hou Mingming Jia Ping Shi Liangju Yu 《Journal of the Indian Society of Remote Sensing》2014,42(3):621-631
Sandy beaches of the eastern coast zone in Eastern Laizhou Bay represent the most popular tourist, recreational destinations and constitute some of the most valuable restates in China. This paper presents the detection of shoreline changes in Laizhou Bay East Bank using an automatic histogram thresholding algorithm on the basis of multi-temporal Landsat images. Shoreline change rates (SCR) and shoreline change areas (SCA) were retrieved using the statistical approach and zonal change detection method, respectively. Results showed that during 1979–2010 a large portion (over 59.8 %) of shoreline are dominated by a retreating process with an average rate of ?2.01 m/year, while other parts of shoreline exhibited a seaward advancing trend due to intense land reclamation activities. It is our anticipation that the result of this work would support sandy beaches protection and management in China coast. 相似文献
13.
Txomin Hermosilla Michael A. Wulder Joanne C. White Nicholas C. Coops Geordie W. Hobart Lorraine B. Campbell 《International Journal of Digital Earth》2016,9(11):1035-1054
Free and open access to the Landsat archive has enabled the implementation of national and global terrestrial monitoring projects. Herein, we summarize a project characterizing the change history of Canada’s forested ecosystems with a time series of data representing 1984–2012. Using the Composite2Change approach, we applied spectral trend analysis to annual best-available-pixel (BAP) surface reflectance image composites produced from Landsat TM and ETM+ imagery. A total of 73,544 images were used to produce 29 annual image composites, generating ～400 TB of interim data products and resulting in ～25 TB of annual gap-free reflectance composites and change products. On average, 10% of pixels in the annual BAP composites were missing data, with 86% of pixels having data gaps in two consecutive years or fewer. Change detection overall accuracy was 89%. Change attribution overall accuracy was 92%, with higher accuracy for stand-replacing wildfire and harvest. Changes were assigned to the correct year with an accuracy of 89%. Outcomes of this project provide baseline information and nationally consistent data source to quantify and characterize changes in forested ecosystems. The methods applied and lessons learned build confidence in the products generated and empower others to develop or refine similar satellite-based monitoring projects. 相似文献
14.
Suspended sediment yield is a very important environmental indicator within Amazonian fluvial systems, especially for rivers dominated by inorganic particles, referred to as white water rivers. For vast portions of Amazonian rivers, suspended sediment concentration (SSC) is measured infrequently or not at all. However, remote sensing techniques have been used to estimate water quality parameters worldwide, from which data for suspended matter is the most successfully retrieved. This paper presents empirical models for SSC retrieval in Amazonian white water rivers using reflectance data derived from Landsat 5/TM. The models use multiple regression for both the entire dataset (global model, N = 504) and for five segmented datasets (regional models) defined by general geological features of drainage basins. The models use VNIR bands, band ratios, and the SWIR band 5 as input. For the global model, the adjusted R2 is 0.76, while the adjusted R2 values for regional models vary from 0.77 to 0.89, all significant (p-value < 0.0001). The regional models are subject to the leave-one-out cross validation technique, which presents robust results. The findings show that both the average error of estimation and the standard deviation increase as the SSC range increases. Regional models were more accurate when compared with the global model, suggesting changes in optical proprieties of water sampled at different sampling stations. Results confirm the potential for the estimation of SSC from Landsat/TM historical series data for the 1980s and 1990s, for which the in situ database is scarce. Such estimates supplement the SSC temporal series, providing a more comprehensive SSC temporal series which may show environmental dynamics yet unknown. 相似文献
15.
全面掌握城市不透水面变化规律和现状,对于城市化进程研究、城市规划发展和生态文明建设等具有重要的意义。以宁波市为研究区,基于1987-2015年的Landsat影像,利用完全约束最小二乘混合像元分解法实现宁波市不透水面信息提取,结果表明:完全约束最小二乘混合像元分解法避免了不透水面丰度出现负值的情况,提取精度较好;近30年宁波市不透水面扩张显著,不透水面面积增长近5倍,扩张速率和强度在2007-2010年达到最大,并逐渐趋于平稳,2007年以前宁波市城市扩张以三江口片和各区县(市)主城区为主,2007年后则以新区经济发展带扩张为主。 相似文献
16.
Forest cover disturbances due to processes such as logging and forest fires are a widespread issue especially in the tropics, and have heavily affected forest biomass and functioning in the Brazilian Amazon in the past decades. Satellite remote sensing has played a key role for assessing logging activities in this region; however, there are still remaining challenges regarding the quantification and monitoring of these processes affecting forested lands. In this study, we propose a new method for monitoring areas affected by selective logging in one of the hotspots of Mato Grosso state in the Brazilian Amazon, based on a combination of object-based and pixel-based classification approaches applied on remote sensing data. Logging intensity and changes over time are assessed within grid cells of 300 m × 300 m spatial resolution. Our method encompassed three main steps: (1) mapping forest/non-forest areas through an object-based classification approach applied to a temporal series of Landsat images during the period 2000–2015, (2) mapping yearly logging activities from soil fraction images on the same Landsat data series, and (3) integrating information from previous steps within a regular grid-cell of 300 m × 300 m in order to monitor disturbance intensities over this 15-years period. The overall accuracy of the baseline forest/non-forest mask (year 2000) and of the undisturbed vs disturbed forest (for selected years) were 93% and 84% respectively. Our results indicate that annual forest disturbance rates, mainly due to logging activities, were higher than annual deforestation rates during the whole period of study. The deforested areas correspond to circa 25% of the areas affected by forest disturbances. Deforestation rates were highest from 2001 to 2005 and then decreased considerably after 2006. In contrast, the annual forest disturbance rates show high temporal variability with a slow decrease over the 15-year period, resulting in a significant increase of the ratio between disturbed and deforested areas. Although the majority of the areas, which have been affected by selective logging during the period 2000–2014, were not deforested by 2015, more than 70% of the deforested areas in 2015 had been at least once identified as disturbed forest during that period. 相似文献
17.
This study integrates the RUSLE, remote sensing and GIS to assess soil loss and identify sensitive areas to soil erosion in the Nilufer creek watershed in Bursa province, Turkey. The annual average soil loss was generated separately for years 1984 and 2011, in order to expose possible soil loss differences occurred in 27 years. In addition, sediment accumulation and sediment yield of the studied watershed was also predicted and discussed. The results indicated that very severe erosion risk areas in 1984 was 13.4% of the area, but it was increased to 15.3% by the year 2011, which needs immediate attention from soil conservation point of view. Furthermore, the estimated annual sediment yield of the Nilufer creek watershed was increased from 903 to 979 Mg km?2 y?1 in 27 years period. The study also provides useful information for decision-makers and planners to take appropriate land management practices in the area. 相似文献
18.
AbstractThis study used multi-date Landsat images to quantify mangrove cover changes in the whole of Bangladesh from 1976 to 2015. Images were pre-processed with an atmospheric correction using Dark Object Subtraction (DOS) and Relative Radiometric Normalization (RRN) using Pseudo-Invariant Features (PIFs). Land Use/Land Cover (LU/LC) classification map was generated using Maximum Likelihood (MaxLike) algorithm, indicating the areal extent of mangroves increased by 3.1% between 1976 and 2015, where 1.79% of this increase occurred between 2000 and 2015. Though mangrove areas remained almost constant in the Sundarbans, Chakaria Sundarbans has almost disappeared between 1976 and 1989. The overall accuracy of Landsat MSS, TM, ETM+, and L8 OLI classified images were 80%, 80%, 87%, and 97% respectively. The study also found deforestation, shrimp & salt farm, coastal erosion and sedimentation, and mangrove plantation could be responsible for mangrove changes in Bangladesh. 相似文献