光学影像纹理信息在林业领域的最新应用进展   总被引：3，自引：1，他引：2  

陈玲  郝文乾  高德亮 《北京林业大学学报》2015,37(3):1-12

随着光学卫星影像空间分辨率的不断提高,影像纹理特征的重要性日益凸显。然而,纹理是一个非常复杂的空间属性,会随着太阳/观测角度、地形、感兴趣目标及其所处环境的不同而发生显著的变化。此外,不同纹理变量的选择及相应输入参数的设置,如窗口大小、像元间距、方向以及量化等级等都可能在一定程度上决定着影像纹理的利用价值。如何有效利用纹理量及其优化组合是一个值得深入探讨的问题。鉴于此,本文首先全面回顾了影像纹理特征在森林分类、森林结构参数反演以及森林生物量与碳储量的遥感估算等方面的最新研究与应用,并从不同角度肯定了光学影像纹理在林业遥感领域的应用潜力。此外,从纹理变量及其4大输入参数的选择和最优变量组合的判别方面,总结并剖析了当前研究领域中所存在的关键问题,权衡利弊并给出了相应的建议,为相关研究人员将影像纹理信息更有效地应用于林业领域提供参考。   相似文献   

Mapping water,oxygen, and pH dynamics in the rhizosphere of young maize roots     

《植物养料与土壤学杂志》2017,180(3):336-346

Rhizosphere processes are highly dynamic in time and space and strongly depend on each other. Key factors influencing pH changes in the rhizosphere are root exudation, respiration, and nutrient supply, which are influenced by soil water content levels. In this study, we measured the real‐time distribution of soil water, pH changes, and oxygen distribution in the rhizosphere of young maize plants using a recently developed imaging approach. Neutron radiography was used to capture the root system and soil water distribution, while fluorescence imaging was employed to map soil pH and soil oxygen changes. Germinated seeds of maize (Zea mays L.) were planted in glass rhizotrons equipped with pH and oxygen‐sensitive sensor foils. After 20 d, the rhizotrons were wetted from the bottom and time‐lapsed images via fluorescence and neutron imaging were taken during the subsequent day and night cycles for 5 d. We found higher water content and stronger acidification in the first 0.5 mm from the root surface compared to the bulk soil, which could be a consequence of root exudation. While lateral roots only slightly acidified their rhizosphere, crown roots induced stronger acidification of up to 1 pH unit. We observed changing oxygen patterns at different soil moisture conditions and increasing towards lateral as well as crown roots while extending laterally with ongoing water logging. Our work indicates that plants alter the rhizosphere pH and oxygen also depending on root type, which may indirectly arise also from differences in age and water content changes. The results presented here were possible only by combining different imaging techniques to examine profiles at the root‐soil interface in a comprehensive way during wetting and drying.  相似文献   

Assessing the utility of ALOS PALSAR and SPOT 4 to predict timber volumes in even-aged Eucalyptus plantations located in Zululand,South Africa     

Riyad Ismail  Horst Kassier  Morries Chauke  Francesco Holecz  Nico Hattingh 《Southern Forests》2015,77(3):203-211

In commercial forestry, regular terrestrial enumerations of the growing stock are required for the valuation, sustain-able management and planning of current and future timber supplies. In this study we examined whether the combination of synthetic aperture radar (ALOS PALSAR) and optical satellite (SPOT 4) image data can accurately predict the timber volume of even-aged Eucalyptus plantations located in South Africa. Results from this study show that the combination of ALOS PALSAR and SPOT 4 produces a R ² value of 0.68 for the planted model, whereas the coppiced model produced a R ² value of 0.55. However, by including stand age as an independent variable in the stepwise model, there was a 15% improvement for the planted model, whereas the coppiced model produced a 27% improvement. The final model developed in this study produced a R ² value of 0.83 and a RMSE of 31.71?m³ ha?1 for planted stands, whereas the model for coppiced stands produced a R ² value of 0.82 and a RMSE of 27.70?m³ ha?1. As it is not practical or financially feasible for commercial forestry companies to carry out terrestrial enumerations for all plantations on an annual basis, the model developed in this study presents an alternative and accurate method to calculate timber volume for even-aged Eucalyptus plantations.  相似文献   

Development of a Vehicle-Mounted Crop Detection System     

ZHONG  Zhen-jiang SUN  Hong LI  Min-zan ZHANG  Feng LI  Xiu-hua 《中国农业科学(英文版)》2014,(6):1284-1292

In order to monitor plant chlorophyll content in real-time, a new vehicle-mounted detection system was developed to measure crop canopy spectral characteristics. It was designed to work as a wireless sensor network with one control unit and one measuring unit. The control unit included a personal digital assistant （PDA） device with a ZigBee wireless network coordinator. As the coordinator of the whole wireless network, the control unit was used to receive, display and store all the data sent from sensor nodes. The measuring unit consisted of several optical sensor nodes. All the sensor nodes were mounted on an on-board mechanical structure so that the measuring unit could collect the canopy spectral data while moving. Each sensor node contained four optical channels to measure the light radiation at the wavebands of 550, 650, 766, and 850 nm. The calibration tests veriifed a good performance in terms of the wireless transmission ability and the sensor measurement precision. Both stationary and moving ifeld experiments were also conducted in a winter wheat experimental ifeld. There was a high correlation between chlorophyll content and vegetation index, and several estimation models of the chlorophyll content were established. The highest R2 of the estimation models was 0.718. The results showed that the vehicle-mounted crop detection system has potential for ifeld application.  相似文献   

Assessment of the use of spectral domain optical coherence tomography (SD‐OCT) for evaluation of the healthy and pathological cornea in dogs and cats     

Frank Famose 《Veterinary ophthalmology》2014,17(1):12-22

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利用MODIS数据反演植被指数的敏感性研究     

张婕  张武  陈权亮 《西南大学学报(自然科学版)》2011,33(11)

根据Kaufman等提出的暗像元法,通过6S辐射传输模式,对MODIS的红光、蓝光、近红外通道辐射特性进行了敏感性实验.结果表明:三个通道的行星反射率对地表反射率都非常敏感,行星反射率随地表反射率的增加而增加.进一步提出了对地表反射率进行大气订正的思路,讨论了暗像元法确定地表反射率误差对大气气溶胶光学厚度反演结果的影响.最后计算分析了光学厚度反演误差对地表反射率大气订正传递误差的大小及其对NDVI、SAVI、ARVI和EVI 4种植被指数计算结果的影响.光学厚度误差对植被指数反演误差的影响以ARVI最为敏感,其误差范围与气溶胶光学厚度误差可达同一量级,两者呈负相关;NDVI与SAVI误差变化范围大致相近,与光学厚度误差均呈负相关.EVI受气溶胶光学厚度误差影响最小.  相似文献   

巢湖秋冬季水体生物光学特性对比研究   总被引：2，自引：0，他引：2  

张运林  朱广伟  吴生才  陈伟民  杨顶田 《农业环境科学学报》2004,23(5):949-953

基于2002-2003年秋、冬2季原位水下光场观测资料，分析了巢湖不同湖区水体的生物光学特性，探讨了水下辐照度光谱分布，光衰减系数的光谱分布、季节变化及湖区分布，影响光衰减系数的主要因子。结果表明，水表面光谱最强出现在550-560nm绿光波段，水下光谱在紫光波段衰减最强烈，其次是蓝、绿光，红光衰减最弱，随着深度增加，绿、红光在整个光谱成分中比例越来越高；秋季360-750nm波段衰减系数在1．29—11．66m^-1间变化，冬季在1．56—18．01m^-1间变化；光衰减系数的空间分布是位于巢湖东部的C4点要好于中西部的C1—C3；光学衰减系数随着波长的增加大致呈下降趋势，但到近红外又有所增加；衰减系数跟悬浮物的相关性最好，平均相关系数平方为0．55，其次是溶解性有机碳，为0．32，跟叶绿素a的相关性最弱，仅为0．27，衰减系数与悬浮物、溶解性有机碳、叶绿素a的多元线性回归在短波部分要好于长波部分。  相似文献   

多通道鱼苗计数器光电微机控制系统设计   总被引：2，自引：0，他引：2  

易金根  黄桂林 《农业工程学报》1997,13(4):171-173

介绍了多通道鱼苗计数器采用光／电／微机一体化设计原理及方法，并给出主要电路程序框图，通过对任一单通道试验结果表明，测鱼管径大小是影响鱼苗计数器准确性的关键因素。  相似文献   

农产品光学参数测量的双积分球系统及其应用   总被引：1，自引：2，他引：1  

徐志龙  王忠义  黄岚  刘志存  侯瑞锋  王成 《农业工程学报》2006,22(11):244-249

为了得到农产品生物组织光学参数，设计了一套双积分球系统实验测量装置。文中描述了其测量原理、系统组成和测量技术，采用650 nm的半导体激光器作为光源，对Intralipid溶液和Evans Blue溶液进行了实际测量，验证了该测量系统的准确性。通过实测，纯牛奶的散射系数为27.719±0.836，吸收系数为0.014±0.001，各向异性因子g=0.846±0.002。通过与其它测量方法对照，相对误差小于5%，该装置能够较准确地获得样品的散射与吸收系数，使之适用于农产品(如果品蔬菜、动物肉、牛奶等)光学参数的测量。  相似文献   

基于暗目标法和GF-1的农作物光合有效辐射反演     

王利民  杨玲波  刘佳  杨福刚  邵杰  姚保民 《农业工程学报》2016,32(22):184-191

光合有效辐射是农田生产力和产量估算的依据,也是农作物参数遥感反演的主要研究内容。该文基于大气辐射传输模型,选择覆盖山东禹城市2014年4月－2014年12月共12景GF-1/WFV（wide field view,WFV）数据,结合浓密植被（暗目标）蓝光波段、红光波段之间反射率的线性关系,基于查找表（look-up table,LUT）技术反演了大气气溶胶光学厚度（aerosol optical depth,AOD）等大气参数,提出了基于蓝、绿、红3个离散波段反演光合有效辐射（photosynthetically available radiation,PAR）的算法。其中,浓密植被是根据WFV/NDVI（normal differential vegetation index）设置阈值的方式筛选的;红光波段与蓝光波段地表反射率的比例系数为1.7977,截距为0.0034,相关系数达0.9826,是根据美国地质调查局（U.S. Geological Survey,USGS）提供的典型植被波谱库数据理论计算获取;GF-1/WFV数据蓝、绿、红波段转换为400～700 nm谱段间光合有效辐射值之间的转换系数分别为0.09156、0.09951、0.1007。采用中国生态系统研究网络禹城实验站实测的 PAR 数据进行对比验证,光合有效辐射的总体精度达到了95.77%,误差绝对值平均为11.36 W/m2,平均误差小于5%,表明了该方法具有较高的精度。该方法不需要额外辅助数据,产品生产过程简单,是比较理想的GF-1/WFV数据光合有效辐射业务反演备选算法。  相似文献