共查询到16条相似文献，搜索用时 125 毫秒
1.
偏振激光雷达探测大气—水体光学参数廓线 总被引：2，自引：2，他引：0
激光雷达在上层水体垂直廓线的遥感中展现出巨大优势。本文研制了一套高垂直分辨率的实时探测偏振激光雷达,提出了一种基于偏振激光雷达回波信号的反演算法,采用Fernald理论和多次散射原理反演非均匀大气—水体的衰减和退偏光学产品,以高效稳定地处理偏振激光雷达实验数据。展示了一个中国内陆水体激光雷达探测实例,观测到了两次气溶胶积聚现象和一次水体浑浊现象。对实验数据的分析表明,退偏比主要由前向多次散射和后向单次散射产生的退偏两部分组成。当多次散射强度较大时,退偏比的变化主要取决于多次前向散射退偏;反之,则主要依赖于单次后向散射退偏。 相似文献
2.
海洋激光雷达多次散射回波信号建模与分析 总被引：1，自引：1，他引：0
海洋激光雷达是实现上层海水3维探测的重要工具,激光在海水中的传输伴随着复杂的多次散射效应,建立准确的海洋激光雷达多次散射回波信号模型有助于实现海水光学特性的高精度反演。本文介绍了仿真海洋激光雷达多次散射信号的解析模型、半解析MC(Monte Carlo)仿真方法和传统MC仿真方法,定量对比分析了不同工作条件下3种模型的仿真结果,讨论了工作高度、接收视场角、水质和水体分层等因素对仿真结果的影响。研究表明:3种模型具有高度一致的仿真结果,但在计算效率方面,解析模型优于半解析MC法,半解析MC法优于传统MC法。解析模型优异的计算效率和可靠的计算精度使其在海洋激光雷达辐射传递机理及应用的研究中具有显著优势。 相似文献
3.
4.
太湖草型湖区底质对遥感反射比的贡献 总被引：1，自引：0，他引：1
水体的光谱特性主要表现为体散射而非表面反射,光学浅水中,光穿透水体而到达水底,离水辐射包含水体自身的贡献以及底质反射并透过水体到达水面的贡献.2004年10月试验获取了太湖67个样点的遥感反射比、后向散射以及吸收等表观光学量和固有光学量,同时测量了叶绿素、悬浮物和DOC含量,以及其他相关参数,如透明度、水深;以草泥均匀分布的水平朗伯性湖底、均质水体为假设条件,使用LEE模型,计算了太湖草型湖区底质对恰在水面下遥感反射比的贡献,同时计算了漫垂直衰减系数;分析了漫垂直衰减系数与透明度、悬浮颗粒以及与无机悬浮颗粒的关系,同时分析了漫垂直衰减系数与底质贡献的关系,从而为太湖水质参数遥感反演精度的提高打下了良好的基础并有了定量判断底质贡献的科学依据. 相似文献
5.
一种计算水体中悬浮物后向散射系数的方法 总被引：1，自引：0，他引：1
基于生物光学模型的水质参数反演分析方法是水质遥感监测算法的发展趋势.分析方法中需要以水体中悬浮物后向散射系数作为参数.水体中悬浮物后向散射系数目前主要有3种测量方法,但是这些方法要么因为仪器稀缺而无法普及,要么测量精度不高.提出了一种计算水体中的悬浮物后向散射系数的方法,该方法利用水面比较容易测量的反射率光谱和实验室内比较容易测量的水体各组分的吸收系数光谱,基于生物光学模型推导得出水体中的悬浮物后向散射系数.利用太湖梅梁湾试验区获取的数据检验了这种方法,并取得了较好的效果.这种方法的主要优势是:它基于生物光学模型,有严密的理论基础,具有较高的精度和通用性;另外,它使用的数据比较容易测量,方法容易实施,可为水质参数反演分析方法的建立奠定坚实的数据基础. 相似文献
6.
唐军武 陈戈 陈卫标 赵朝方 贺岩 吴松华 刘秉义 毛志华 何惠馨 杨杰 陈树果 胡连波 何兴道 史久林 郑永超 刘建强 林明森 吴立新 郭华东 蒋兴伟 潘德炉 顾逸东 《遥感学报》2021,25(1):460-500
本文从海洋与气候变化等重大前沿科学与应用对空间海洋观测系统的需求出发,基于当前国内外空间激光技术水平与前期海洋激光遥感的探索,提出了海洋遥感从二维向三维发展的紧迫性,并将海洋剖面探测激光雷达作为未来“海洋三维遥感”的主要技术手段。本文对近50年国内外激光海洋剖面探测技术的理论与应用、基础性关键探测机理问题,尤其是近10年来的试验性探索及其在多个海洋科学问题中的应用进行了综述。结合中国自主“观澜号”海洋科学卫星计划中海洋剖面探测激光雷达的系统论证与指标要求,提出了未来海洋剖面探测激光雷达发展路线图建议以及中国有望率先在空间海洋剖面激光探测领域取得突破的设想。 相似文献
7.
8.
气溶胶激光雷达的国内外研究进展与展望 总被引：1，自引：0，他引：1
大气气溶胶具有显著的环境与气侯效应,而定量评估上述效应需要准确了解气溶胶物理化学光学性质的时空分布特征。过去几十年,激光雷达已被国内外学者广泛应用于气溶胶探测研究,主要依赖于其在探测范围、时空分辨率等方面具有独特的技术优势。本文主要总结激光雷达在探测气溶胶方面的国内外研究进展,首先简要介绍可用于探测气溶胶的主要激光雷达类型,然后分别根据气溶胶大小、组分、浓度、形状、光学性质等关键信息介绍相关研究进展,最后进行总结并对气溶胶激光雷达发展进行了展望。 相似文献
9.
10.
吸收系数是水体的固有光学参数,是进行水体光学遥感研究的基础。讨论了一种基于人工神经网络(artifi-cial neural networks,ANN)、利用遥感反射比数据反演水体吸收系数的方法。该方法用实测的水体遥感反射比(Rrs)数据集建立BP神经网络,用以反演水体在波长440 nm处的吸收系数(α(440))。实测遥感反射比数据集的80%数据用于训练样本,20%数据用于预测样本。研究结果表明:正确选择神经网络的传递函数、训练函数和隐含层节点个数是至关重要的;用最优的传递函数、训练函数和隐含层节点个数得到的预测结果与实际测量结果的相关系数高达0.978,证明了该方法的可行性。 相似文献
11.
The airborne lidar system (ALS) provides a means to efficiently monitor the status of remote tropical forests and continues to be the subject of intense evaluation. However, the cost of ALS acquisition can vary significantly depending on the acquisition parameters, particularly the return density (i.e., spatial resolution) of the lidar point cloud. This study assessed the effect of lidar return density on the accuracy of lidar metrics and regression models for estimating aboveground biomass (AGB) and basal area (BA) in tropical peat swamp forests (PSF) in Kalimantan, Indonesia. A large dataset of ALS covering an area of 123,000 ha was used in this study. This study found that cumulative return proportion (CRP) variables represent a better accumulation of AGB over tree heights than height-related variables. The CRP variables in power models explained 80.9% and 90.9% of the BA and AGB variations, respectively. Further, it was found that low-density (and low-cost) lidar should be considered as a feasible option for assessing AGB and BA in vast areas of flat, lowland PSF. The performance of the models generated using reduced return densities as low as 1/9 returns per m2 also yielded strong agreement with the original high-density data. The use model-based statistical inferences enabled relatively precise estimates of the mean AGB at the landscape scale to be obtained with a fairly low-density of 1/4 returns per m2, with less than 10% standard error (SE). Further, even when very low-density lidar data was used (i.e., 1/49 returns per m2) the bias of the mean AGB estimates were still less than 10% with a SE of approximately 15%. This study also investigated the influence of different DTM resolutions for normalizing the elevation during the generation of forest-related lidar metrics using various return densities point cloud. We found that the high-resolution digital terrain model (DTM) had little effect on the accuracy of lidar metrics calculation in PSF. The accuracy of low-density lidar metrics in PSF was more influenced by the density of aboveground returns, rather than the last return. This is due to the flat topography of the study area. The results of this study will be valuable for future economical and feasible assessments of forest metrics over large areas of tropical peat swamp ecosystems. 相似文献
12.
基于葵花-8卫星大气产品的地表下行短波辐射计算 总被引：2，自引：2，他引：0
地表下行短波辐射DSSR(Downward Surface Shortwave Radiation)的准确估算在气候变化研究和地表太阳能估算等领域具有重要作用。新一代静止气象卫星葵花-8(Himawari-8)具有高达10 min的对地观测能力,为DSSR近实时估算提供了新机遇。然而,日本宇宙航空研究开发机构(JAXA)对外公开的葵花-8辐射产品中,没有将其反演的云、气溶胶产品作为DSSR的输入参数,从而没有形成一整套的DSSR估算算法流程,缺乏产品输出的一致性。大气中的云、气溶胶是DSSR的重要影响因子,本文重点考虑云、气溶胶对太阳辐射的影响,基于大气辐射传输模式RSTAR构建了DSSR查找表,开发了DSSR的快速计算方法,进而将JAXA葵花-8二级云、气溶胶产品(光学厚度,粒子有效半径等)作为快速化计算方法的输入参量,计算得到了DSSR。通过与JAXA葵花-8二级DSSR产品(JAXA DSSR)对比,发现两者具有很好的空间一致性。为了进一步评价本文的DSSR计算精度,分别选取了陆地(Yonsei)和海洋(0n_165e)的观测数据验证了2016年4、7、10和12月本文计算的DSSR和同时期的JAXA DSSR产品,验证结果显示两者的DSSR在两个观测站点均具有非常高的相关性(全天空、晴空和云天条件下的相关系数R均大于0.88)。在两个站点云天条件下的验证结果中,考虑了云相态并在冰云模型中使用了非球形冰晶粒子(六棱柱)来计算DSSR,获得了比JAXA DSSR更小的偏差。本文提出的快速化计算方法能快速准确地计算DSSR,可为计算地表辐射收支等研究提供重要数据支撑。 相似文献
13.
This article investigates the performance of MERIS reduced resolution data to monitor water quality parameters in the Berau estuary waters, Indonesia. Total suspended matter (TSM), Chlorophyll-a (Chl-a) concentration and diffuse attenuation coefficient (Kd ) were derived from MERIS data using three different algorithms for coastal waters: standard global processor (MERIS L2), C2R and FUB. The outcomes were compared to in situ measurements collected in 2007. MERIS data processed with C2R gave the best retrieval of Chl-a, while MERIS L2 performed the best for TSM retrieval, but large deviations from in situ data were observed, pointing at inversion problems over these tropical waters for all standard processors. Nevertheless, MERIS can be of use for monitoring equatorial coastal waters like the Berau estuary and reef system. Applying a Kd (490) local algorithm to the MERIS RR data over the study area showed a sufficient good correlation to the in situ measurements (R 2 = 0.77). 相似文献
14.
Diofantos G Hadjimitsis 《Transactions in GIS》2008,12(5):633-644
Satellite sensors have provided new datasets for monitoring regional and urban air quality. Satellite sensors provide comprehensive geospatial information on air quality with both qualitative remotely sensed imagery and quantitative data, such as aerosol optical depth which is the basic unknown parameter for any atmospheric correction method in the pre‐processing of satellite imagery. This article presents a new method for retrieving aerosol optical thickness directly from satellite remotely sensed imagery for short wavelength bands in which atmospheric scattering is the dominant contribution to the at‐satellite recorded signal. The method is based on the determination of the aerosol optical thickness through the application of the contrast tool (maximum contrast value), the radiative transfer calculations and the ‘tracking’ of the suitable darkest pixel in the scene. The proposed method that needs no a‐priori information has been applied to LANDSAT‐5 TM, LANDSAT‐7 ETM+, SPOT‐5 and IKONOS data of two different geographical areas: West London and Cyprus. The retrieved aerosol optical thickness values show high correlations with in‐situ visibility data acquired during the satellite overpass. Indeed, for the West London area a logarithmic regression was fitted for relating the determined aerosol optical thickness with the in‐situ visibility values. A high correlation coefficient (r2= 0.82; p= 0.2) was found. Plots obtained from Tanre et al. (1979, 1990) and Forster (1984 ) were reproduced and estimates for these areas were generated with the proposed method so as to compare the results. The author's results show good agreement with Forster's aerosol optical thickness vs. visibility results and a small deviation from Tanre's model estimates. 相似文献
15.
Evaluation of a three-band model for estimating chlorophyll-a concentration in tidal reaches of the Pearl River Estuary, China 总被引：1，自引：0，他引：1
Shuisen Chen Ligang Fang Hongli Li Weiqi Chen Wenrui Huang 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(3):356-364
Accurate assessment of phytoplankton chlorophyll-a (Chla) concentration in turbid waters by means of remote sensing was challenging due to the optical complexity of turbid waters. Recently, a conceptual model containing reflectance in three spectral bands in the red and near-infrared range of the spectrum was suggested for retrieving Chla concentrations in turbid productive waters. The objective of this paper was to evaluate the performance of this three-band model to estimate Chla concentration in the Pearl River Estuary (PRE), China. Reflectance spectra of surface water and water samples were collected concurrently. The samples contained variable Chla (4.80-92.60 mg/m3) and total suspended solids (0.4-55.2 mg/L dry wt). Colored dissolved organic matter (CDOM) absorption at 400 nm was 0.40-1.41 m−1; turbidity ranged from 4 to 25 NTU (Nephelometric Turbidity Units). The three-band model was spectrally calibrated by iterative and least-square linear regression methods to select the optimal spectral bands for the most accurate Chla estimation. Strong linear relationships (R2=0.81, RMSE=1.4 mg/m3, N=32) were established between measured Chla and the levels obtained from the calibrated three-band model [R−1(684)-R−1(690)]×R(718), where R(λ) was the reflectance at wavelength λ. The calibrated three-band model was independently validated (R2=0.9521, RMSE=6.44 mg/m3, N=16) and applied to retrieve Chla concentrations from the calibrated EO-1 Hyperion reflectance data in the PRE on December 21, 2006. The EO-1 Hyperion-derived Chla concentrations were further validated using synchronous in situ data collected on the same day (R2=0.64, RMSE=2 mg/m3, N=9). The spatial tendency of Chla distribution mapping by Hyperion showed gradually increased concentrations of Chla farther from the river mouths (although decreasing from east to west), which were disturbed by the combination of river outlets and tidal current in Lingding Bay of the PRE. This observation conformed to previous observations and studies, and could reasonably be explained by geographical changes. Also, results indicated that the slope of the three-band regression line decreased as the Chla concentration increased, resulting in the first sensitive band of the three-band model to move towards short wavelengths. These findings validated the rationale behind the conceptual model and demonstrated the robustness of this algorithm for Chla retrieval from in situ data and the Hyperion satellite sensor in turbid estuarine waters of the PRE, China. 相似文献
16.
机载WIDAS地表观测的BRDF原型反演算法验证 总被引：1，自引：1，他引：0
地表反照率表征地面对太阳辐射的反射能力,在地表能量平衡中起着重要的作用。2008年黑河的WATER实验中,针对机载红外广角双模式成像仪(WIDAS)观测角度小的特点,发展了一种基于MODIS二向性反射分布函数(BRDF)原型估算WIDAS反照率的算法。然而,在2012年黑河HiWATER实验中,WIDAS的观测角度范围由早期30°观测天顶角升级为最大观测天顶角52°,这一改造对数据预处理(辐射定标、大气校正和多角度配准)产生影响,使WIDAS数据出现明显的噪声,为WIDAS地表反照率的反演带来新挑战。针对新问题,采用新的地表观测数据,进一步验证了BRDF原型算法反演机载WIDAS反照率的能力。为了获取准实时BRDF先验知识,基于核驱动模型和各向异性平整指数(AFX)首先准实时提取了实验区5种MODIS的BRDF原型;然后,将其作为先验知识应用到黑河WIDAS机载数据的反照率反演中;最后,利用实验区的反照率实测数据进行算法验证。本研究比较了3个算法处理该问题的能力:(1)基于BRDF原型作为先验知识的算法;(2)完全基于核驱动的全反演算法;(3)基于朗伯假设的方法,通过算法对比分析,可更好地分析验证算法(1)的性能。结果表明:(1)BRDF原型算法反演精度最高且稳定,尤其是当观测数据位于垂直主平面时,全反演算法由于缺少大角度观测数据的约束,更容易出现异常值;BRDF原型算法的最大绝对误差为0.034,相对于全反演算法和朗伯假设方法精度分别提高了约18%和71%;(2)针对2012年黑河机载WIDAS观测噪声较大的新问题,BRDF原型反演算法表现出了良好的抗噪声性能。通过对WIDAS反照率反演和验证进一步表明,在多角度观测数据信息量不足以进行全反演,且观测受噪声影响较大时,BRDF原型作为先验知识,提供了一种有效解决该问题的手段,对提高反照率反演的精度、增强反演的稳定性有重要作用。 相似文献