多维信息在改善沿海地区图像分类精度中的应用方法

在某些专题研究中,由于研究目标、大气传输、下垫面及其他因素的限制,波谱分析的统计分类模式并不能完全满足研究需要。虽然多时相高精度图像可以提高分类精度,但常因其费用相当昂贵而难以实现。因此,如何在现有资料基础上,提取更多有效信息是亟需解决的问题。针对沿海地区特有的复杂地理现象,以TM图像为基础,通过量化手段进行最佳信息维数的确定与最佳信息维数组合的选择,探讨了信息维数对分类精度的影响。结果表明,在原有图像基础上,进行信息挖掘并重新组合可以得到能满足工作需要的分类精度,组合维数以6维最佳,更多的信息融合对精度影响不明显。     

Ocean Color Satellite Imagery and Shipboard Measurements of Chlorophyll a and Suspended Particulate Matter Distribution in the East China Sea

Satellite-derived ocean color data of Coastal Zone Color Scanner (CZCS) on board the Nimbus-7 and Ocean Color and Temperature Scanner (OCTS) on board the Advanced Earth Observing Satellite (ADEOS) are jointly used with historical in situ data to examine seasonal and spatial distributions of chlorophyll a (Chl-a) and suspended particulate matter (SPM) concentrations in the East China Sea. Ocean color imagery showed that Chl-a concentrations on the continental shelf were higher than those of the Kuroshio area throughout the year. Satellite-derived Chl-a concentrations are generally in good accordance with historical in situ values during spring through autumn (although no shipboard in situ measurement was conducted at nearshore areas). In contrast, ocean color imagery in winter indicated high Chl-a concentrations (4–10 mg m^–3) on the continental shelf where bottom depth was less than 50 m when surface water was turbid (2–72 g m^–3 of SPM at surface), while historical in situ values were usually less than 1 mg m^–3. This suggests that resuspended bottom sediment due to wind-driven mixing and winter cooling is responsible for the noticeable overestimation of satellite-derived Chl-a concentrations. The algorithm for ocean color needs to be improved urgently for turbid water.     

碱厂废水光谱特性实验研究

该文报道碱厂废水随浓度变化的光谱实验。分析碱厂废水的光谱特征 ,并与相同浓度的海水悬浮泥沙水体的光谱进行比较 ;确定该废水特征波长为 50 1.3nm。根据光谱实验结果 ,结合当前已有的水色传感器的资料 ,选择两个卫星传感器波段 :Sea WIFS第四频道 (497.2～ 52 1.6 nm)和TM第二频道 (518.9～ 6 0 0 .2 nm) ;利用数字对 (R,c) ,建立了反射率与该污染水体浓度间的相关模式。为遥感技术大面积、快速地监测碱厂废水污染水体提供理论依据。     

Seasonal variation of suspended-sediment transport through the southern Bohai Strait

Based on field observations made in winter 2006 and summer 2007 and on multiscene MODerate resolution Imaging Spectrometer (MODIS) imagery, the seasonal variation of suspended-sediment transport in the southern Bohai Strait and its possible mechanisms are examined. The field observations in two different seasons allow an exponential empirical model to be used to retrieve suspended-sediment concentration (SSC) from MODIS imagery. Both the field-survey data and the MODIS-derived SSC show that the sediment transport in the southern Bohai Strait has a significant seasonal variation due to the seasonally varying thermohaline structure of the water column and the hydrodynamics resulting from the seasonally alternating monsoons. The SSC in winter is approximately 3–10 times higher than in summer. Considering the seasonal variation of water flux (WF) and SSC, the annual sediment flux (SSF) through the southern Bohai Strait is estimated to be approximately 40.0 Mt yr⁻¹, about 4–8 times previous estimates, which did not take into account seasonal variation. Although the Huanghe (Yellow River) discharges a large amount of sediment in the summer, the SSF through the southern Bohai Strait in the winter (∼32.0 Mt) is about 4 times greater than it is in the summer. The strong seasonal variability of SSF through the southern Bohai Strait indicates that strong resuspension along the coast of the Huanghe delta in winter and enhanced longshore transport by coastal currents due to winter monsoon activity might be the major mechanisms of cross-strait transport of sediment in winter.     

腾格里沙漠地区盐湖资源调查遥感应用研究

通过对腾格里沙漠地区遥感影像信息分析与野外实地调查,圈定出大小盐湖122个,查明了盐湖的空间分布规律,划分了图兰泰湖-头道湖、白碱湖-西硝池、苏武山湖-汤家海、鸡龙同古-和屯、通古楼诺尔-巴彦达来五个盐湖分布区,对各分布区盐湖的成因类型、沉积特征、成矿规律及资源状况进行了研究,为进一步勘查、开发和利用本区资源提供了依据。     

Impact of model development,calibration and validation decisions on hydrological simulations in West Lake Erie Basin

Watershed simulation models are used extensively to investigate hydrologic processes, landuse and climate change impacts, pollutant load assessments and best management practices (BMPs). Developing, calibrating and validating these models require a number of critical decisions that will influence the ability of the model to represent real world conditions. Understanding how these decisions influence model performance is crucial, especially when making science‐based policy decisions. This study used the Soil and Water Assessment Tool (SWAT) model in West Lake Erie Basin (WLEB) to examine the influence of several of these decisions on hydrological processes and streamflow simulations. Specifically, this study addressed the following objectives (1) demonstrate the importance of considering intra‐watershed processes during model development, (2) compare and evaluated spatial calibration versus calibration at outlet and (3) evaluate parameter transfers across temporal and spatial scales. A coarser resolution (HUC‐12) model and a finer resolution model (NHDPlus model) were used to support the objectives. Results showed that knowledge of watershed characteristics and intra‐watershed processes are critical to produced accurate and realistic hydrologic simulations. The spatial calibration strategy produced better results compared to outlet calibration strategy and provided more confidence. Transferring parameter values across spatial scales (i.e. from coarser resolution model to finer resolution model) needs additional fine tuning to produce realistic results. Transferring parameters across temporal scales (i.e. from monthly to yearly and daily time‐steps) performed well with a similar spatial resolution model. Furthermore, this study shows that relying solely on quantitative statistics without considering additional information can produce good but unrealistic simulations. Copyright © 2015 John Wiley & Sons, Ltd.     

黄岩岛环礁地貌近40年变化的遥感分析

重建珊瑚礁的地貌变化历史将有助于理解珊瑚礁对气候变化的响应规律。因此,本文选择以南海中部相对孤立、低潮时部分露出的黄岩岛环礁（15°09'N,117°45'E）为对象,基于1977年至2019年间的Landsat和Sentinel-2共22景遥感影像来探讨南海珊瑚礁地貌的变化历史与规律。首先结合实测水深数据探讨遥感影像灰度的变化与珊瑚礁地貌带分界线位置的对应关系;然后通过基于梯度矢量流的主动轮廓线模型（GVF-Snake）和手动边缘提取相结合的方式,提取出黄岩岛环礁主要的地貌带分界线;进而利用数字化海岸线分析系统（DSAS）定量分析这些地貌带分界线位置的变化,并利用线性拟合来探讨这些地貌面积的变化趋势。结果表明：1）黄岩岛外海与礁前斜坡分界线、礁前斜坡与礁坪分界线、潟湖坡与潟湖底分界线均具有向外海移动的趋势,它们的平均移动速率分别是0.36 m/a、0.06 m/a和0.23 m/a,而礁坪与潟湖坡分界线则具有向潟湖移动趋势,平均移动速率为0.16 m/a;2）潟湖底的面积和礁体总面积都呈现增加的趋势,潟湖坡的面积有减少趋势,礁坪的面积则在1977年至1997年间以114523 m²/a的速率增加,其后在1997年至2019年间则以11289 m²/a的速率减少。进一步分析认为,近40年来,黄岩岛珊瑚礁生态系统退化致使其造礁能力的减弱,加之海平面上升、风暴潮侵蚀、海水溶解等因素的综合影响,导致黄岩岛珊瑚礁面积减少。

     

基于CityGML的遥感信息共享研究

在参考现有地物分类标准和CityGML要素类型基础上,探讨遥感专题模型的设计方法,分析基于CityGML的几何拓扑、语义属性信息表达机制,并以一小区域数据验证了方法的可行性。     

遥感影像构造地质解译过程中的逻辑形式与逻辑规律讨论

遥感图像是地表地物表征的集合，构成影像景观单元。遥感解译属于人脑意识活动的范畴，是利用表层信息由表及里、由此及彼的逻辑推理过程。探求因果联系的科学归纳法，探求等同关系的类比推理法，探求真实性的科学论证法是遥感解译过程中应遵循的思想方法。     

Impact of sub-pixel heterogeneity on modelled brightness temperature for an agricultural region

Knowledge of sub-pixel heterogeneity, particularly at the passive microwave scale, can improve the brightness temperature (and ultimately the soil moisture) estimation. However, the impact of surface heterogeneity (in terms of soil moisture, soil temperature and vegetation water content) on brightness temperature in an agricultural setting is relatively unknown. The Soil Moisture Active Passive Validation Experiment 2012 (SMAPVEX12) provided an opportunity to evaluate sub-pixel heterogeneity at the scale of a Soil Moisture Ocean Salinity (SMOS) or the Soil Moisture Active Passive (SMAP) radiometer footprint using field measured data. The first objective of this study was to determine if accounting for surface heterogeneity reduced the error between estimated brightness temperature (T_b) and T_b measured by SMOS. It was found that when accounting for variation in surface soil moisture, temperature and vegetation water content within the pixel footprint, the error between the modelled T_b and the measured T_b was less than if a homogeneous pixel were modelled. The correlation between the surface parameters and the error associated with not accounting for surface heterogeneity were investigated. It was found that there was low to moderate correlation between the error and the coefficient of variance associated with the measured soil moisture, soil temperature and vegetation volumetric water content during the field campaign. However, it was found that the correlations changed depending on the stage of vegetation growth and the amount of time following a precipitation event. At the start of the field campaign (following a precipitation event), there was strong correlation between the error and all three surface parameters (r ≥ 0.75). Following a precipitation event close to the middle of the field campaign (during which there was rapid growth in vegetation), there was strong correlation between the error and the variability in vegetation water content (r = 0.89), moderate correlation with soil moisture (r = 0.61) and low correlation with soil temperature (r = 0.26).