A New Model for Quantifying Anisotropic Scale Invariance and for Decomposition of Mixing Patterns

A new power–law function has been derived to represent the relationship between area of the set consisting of wave numbers with spectral energy density above S (A(>S)) on the two-dimensional frequency plane and S. The power–law relation holds if the field concerned possessing isotropic scale invariance or generalized scaling invariance involves rotational and ratio-scale changing transforms. The equation is valid for dealing with common exploration geophysical and geochemical fields encountered in mineral exploration and environmental assessment. This power–law function not only provides a new model for characterizing anisotropic scaling invariance for generalized scaling field, for example, estimating the power exponent of power spectrum of generalized scale invariance measure in frequency domain, but also forms a theoretical base for the S–A filtering technique developed for decomposing a mixing field into components on the basis of distinct scaling properties in the frequency domain. It is demonstrated that the method has potential to become a general technique for image processing and pattern recognition.     

干旱区典型绿洲热场分布规律研究——以渭干河-库车河三角洲绿洲为例

 全球气候变暖给整个地球的生态环境带来巨大的影响,在全球气候变暖背景下,绿洲热场的变化严重影响绿洲的生态稳定性,利用遥感卫星影像来监测热场分布规律具有很强的现实意义。采用Landsat7 ETM+热红外波段定量反演晴空状态下干旱区典型绿洲地表真实温度,运用影像叠加分析、直方图比对、缓冲区分析、空间自相关分析及剖面线分析方法,分析其热场分布规律。结果表明,绿洲热场分布具有显著的正的空间自相关特性,Moran’s I值为0.5489,z检验值为48.44,同时呈现出显著的局部空间集聚现象; 就全局而言,热场分布规律为水体温度<耕地温度<林草地温度<城镇温度<裸地温度<盐碱地温度,均温分别为21.65 ℃、27.86 ℃、35.59 ℃、36.52 ℃、40.06 ℃、42.07 ℃; 就局部而言,盐碱地温度低于周边裸地温度,盐碱地平均温度比周边300 m、900 m、1 500 m缓冲区裸地的均温分别低0.59 ℃、0.44 ℃、0.26 ℃。水体、城镇、盐碱地、裸地的温度波动较小,热力景观单一,热场分布均匀,而耕地和林草地的温度梯度大,热力景观复杂多样,热场分布极不均匀。绿洲荒漠交错带的面积较大,它可以降低荒漠对绿洲的热力侵蚀,对保护绿洲有重要作用。     

基于TM影响的不同季节北京城市热环境研究

利用2005～2006年4景北京Landsat TM影像,通过热红外波段反演地表温度,揭示不同季节城市热环境分布特征及其空间差异。分别利用遥感反演的地面温度和地面气象站观测的气温数据,计算地表热岛强度和空气热岛强度,并分析其季节变化,结果表明：城区相对近郊区,热岛效应在夏季显著;城区相对于乡村,四季都存在较强的热岛效应。     

基于OSTU算法利用新型水体指数进行Landsat数据自适应阈值水体自动提取研究

利用Landsat数据,结合NDWI与MNDWI提取水体信息的特点提出了一种新的水体指数NMWI,并结合OSTU算法自适应地确定最佳分割阈值,完成了对海洋、河流、湖泊和水库4种主要的典型水体信息的自动提取,均取得了较好的效果。     

基于TM影像的水体透明度反演模型——以鄱阳湖国家自然保护区为例

以江西鄱阳湖国家自然保护区为例,研究基于Landsat TM 5影像的水体透明度反演模型.结合6个时期的影像与对应的13个实测塞氏盘深度(SDD)数据建立了SDD的自然对数变换值与蓝、红波段的自然对数变换值的线性组合之间的回归模型,即ln(SDD)=-4.016-0.722ln(blue)-0.587ln(red).此模型能够解释88%的水体透明度变化.利用另外12个样点进行模型的检验.检验结果显示实际量测值与模型反演值之间的相关系数为0.93,误差标准差等于0.22 m.因此我们认为此模型获得了可以接受的结果.     

Landsat 8全色影像阴影的扁平冰山出水高度提取

冰山出水高度是测量冰山厚度进而估算冰山体积的一个重要几何参数,是定量评估冰山对海洋的淡水输入量的基础。冬季冰山在海冰上成影且阴影较长,本文提出利用阴影测高模型高精度测量冰山出水高度的方法。试验选择2016年8月29日、9月7日和9月16日中心太阳高度角分别为5.43°、7.49°和11.01°的3期Landsat 8全色15 m影像,以独立扁平冰山为例,自动提取冰山在海冰上的阴影长度计算冰山出水高度,并利用不同时相同名成影点进行交叉验证评估测量精度。结果显示：阴影长度测量误差优于1个像元,在太阳高度角低于11.01°时,全色15 m影像提取的冰山出水高度均方根误差（RMSE）低于2.0 m,平均绝对误差（MAE）低于1.5 m。由此表明：在冬季低太阳高度角下,Landsat 8全色15 m影像可用于高精度测量冰山出水高度,具有大范围测量南极冰山出水高度的潜力。     

Pixel‐oriented land use classification in energy balance modelling

Mass and energy transfer between soil, vegetation and atmosphere is the process that allows to maintain an adequate energy and water balance in the earth–atmosphere system. However, the evaluation of the energy balance components, such as the net radiation and the sensible and latent heat fluxes, is characterized by significant uncertainties related to both the dynamic nature of heat transfer processes and surfaces heterogeneity. Therefore, a detailed land use classification and an accurate evaluation of vegetation spatial distribution are required for an accurate estimation of these variables. For this purpose, in the present article, a pixel‐oriented supervised classification was applied to obtain land use maps of the Basilicata region in Southern Italy by processing three Landsat TM and ETM+ satellite images. An accuracy analysis based on the overall accuracy index and the agreement Khat of Cohen coefficient showed a good performance of the applied classification methodology and a good quality of the obtained maps. Subsequently, these maps were used in the application of a simplified two‐source energy balance model for estimating the actual evapotranspiration at a regional scale. The comparison between the simulations made by applying the simplified two‐source energy balance model and the measurements of evapotranspiration at a lysimetric station located in the study area showed the applicability and the validity of the proposed methodology. Copyright © 2012 John Wiley & Sons, Ltd.     

Exploration of remotely sensed forest structure and ultrasonic range sensor metrics to improve empirical snow models

Current methods to estimate snow accumulation and ablation at the plot and watershed levels can be improved as new technologies offer alternative approaches to more accurately monitor snow dynamics and their drivers. Here we conduct a meta‐analysis of snow and vegetation data collected in British Columbia to explore the relationships between a wide range of forest structure variables – obtained from Light Detection and Ranging (LiDAR), hemispherical photography (HP) and Landsat Thematic Mapper – and several indicators of snow accumulation and ablation estimated from manual snow surveys and ultrasonic range sensors. By merging and standardizing all the ground plot information available in the study area, we demonstrate how LiDAR‐derived forest cover above 0.5 m was the variable explaining the highest percentage of absolute peak snow water equivalent (SWE) (33%), while HP‐derived leaf area index and gap fraction (45° angle of view) were the best potential predictors of snow ablation rate (explaining 57% of variance). This study reveals how continuous SWE data from ultrasonic sensors are fundamental to obtain statistically significant relationships between snow indicators and structural metrics by increasing mean r² by 20% when compared to manual surveys. The relationships between vegetation and spectral indices from Landsat and snow indicators, not explored before, were almost as high as those shown by LiDAR or HP and thus point towards a new line of research with important practical implications. While the use of different data sources from two snow seasons prevented us from developing models with predictive capacity, a large sample size helped to identify outliers that weakened the relationships and suggest improvements for future research. A concise overview of the limitations of this and previous studies is provided along with propositions to consistently improve experimental designs to take advantage of remote sensing technologies, and better represent spatial and temporal variations of snow. Copyright © 2013 John Wiley & Sons, Ltd.     

基于光谱角匹配算法的水体信息提取研究

针对水体信息提取时,传统算法不能较好地解决山体阴影被误提为水体的问题,引入多用于高光谱数据处理的光谱角匹配算法,以Land-sat8 OLI(band1-band7)为数据源,以黄河小浪底水库周边区域为实验区,开展水体信息提取研究,结果显示:水体指数法和波段关系提取的结果中有大量的山体阴影信息,提取精度不超过30%,而光谱角匹配法提取结果受阴影的影响较小,提取精度在99%以上。     

Study of high temperature targets identification and temperature retrieval experimental model in SWIR remote sensing based Landsat8

For surface features in short-wave infrared (SWIR, 1.3–3.0 μm) in remote sensing imagery, pixel values depict the total energy including reflection and emission. For surface features at normal temperature in SWIR band, emission energy can be ignored. While for surface features at high temperature in SWIR band, emission energy is equal to or even higher than the reflection energy. So remote sensing imagery of SWIR band can be used to separate emission and reflection energy as well as to realize temperature retrieval of high temperature targets. In this study, the seventh band (SWIR band) of Landsat8 OLI remote sensing imagery is used to perform the theoretical model research for temperature retrieval of high temperature targets. In the meantime, it is also used with the corresponding observation experiment of synchronization satellite to check the theoretical model. The result shows that the radiant flux density for mixed pixels with high temperature targets is higher than adjacent pixels without high temperature targets. Thus, the high temperature pixels can be identified in SWIR band. The retrieval results of temperature and fractional area for high temperature targets are consistent with reality. In the study, the result illustrates that it is effective to identify high temperature targets in remote sensing imagery of SWIR band and the model is appropriate for temperature retrieval use.