Analysis of common canopy vegetation indices for indicating leaf nitrogen accumulations in wheat and rice

The common spectra wavebands and vegetation indices (VI) were identified for indicating leaf nitrogen accumulation (LNA), and the quantitative relationships of LNA to canopy reflectance spectra were determined in both wheat (Triticum aestivum L.) and rice (Oryza sativa L.). The 810 and 870 nm are two common spectral wavebands indicating LNA in both wheat and rice. Among all ratio vegetation indices (RVI), difference vegetation indices (DVI) and normalized difference vegetation indices (NDVI) of 16 wavebands from the MSR16 radiometer, RVI (870, 660) and RVI (810, 660) were most highly correlated to LNA in both wheat and rice. In addition, the relations between VIs and LNA gave better results than relations between single wavebands and LNA in both wheat and rice. Thus LNA in both wheat and rice could be indicated with common VIs, but separate regression equations are better for LNA monitoring.     

基于月球反射的遥感器定标跟踪监测

月亮辐照度是可见近红外波段一种稳定的辐射参考基准,对月观测已成为星载遥感仪器辐射定标和验证的一种新方法。风云三号03星(FY-3C)中分辨率光谱成像仪(Moderate Resolution Spectral Imager,MERSI)增加了对月观测功能,改进了太阳反射波段的在轨辐射定标。本文收集分析了MERSI在轨工作以来的全部11组对月观测数据,利用通道间辐照度比值方法移除月相角,日—月—星相对距离等因素对月亮辐照度观测值的影响,开展了可见光近红外波段的辐射定标工作,实现了MERSI太阳反射通道的辐射定标系数动态跟踪和评估。通过线性回归及统计发现,通道8辐射响应的年衰减率达到了14.55%,通道9达到了8.42%,通道1、6、10、11、16和19的年衰减率为1.15%—4.72%,其余通道未检测到衰减。研究结果可以用于订正MERSI数据的辐射定标系统性偏差,提高MERSI全寿命期的辐射定标精度。     

Multiple spectral similarity metrics for surface materials identification using hyperspectral data

Modern hyperspectral imaging and non-imaging spectroradiometer has the capability to acquire high-resolution spectral reflectance data required for surface materials identification and mapping. Spectral similarity metrics, due to their mathematical simplicity and insensitiveness to the number of reference labelled spectra, have been increasingly used for material mapping by labelling reflectance spectra in hyperspectral data labelling. For a particular hyperspectral data set, the accuracy of spectral labelling depends considerably upon the degree of unambiguous spectral matching achieved by the spectral similarity metric used. In this work, we propose a new methodology for quantifying spectral similarity for hyperspectral data labelling for surface materials identification. Developed adopting the multiple classifier system architecture, the proposed methodology unifies into a single framework the differential performances of eight different spectral similarity metrics for the quantification of spectral matching for surface materials. The proposed methodology has been implemented on two types of hyperspectral data viz. image (airborne hyperspectral images) and non-image (library spectra) for numerous surface materials identification. Further, the performance of the proposed methodology has been compared with the support vector machines (SVM) approach, and with all the base spectral similarity metrics. The results indicate that, for the hyperspectral images, the performance of the proposed methodology is comparable with that of the SVM. For the library spectra, the proposed methodology shows a consistently higher (increase of about 30% when compared to SVM) classification accuracy. The proposed methodology has the potential to serve as a general library search method for materials identification using hyperspectral data.     

Interception,drop size distributions and rainfall kinetic energy in four colombian forest ecosystems

Interception losses, rain and throughfall drop size spectra and kinetic energy were studied in four relatively undisturbed tropical forest ecosystems along a transect across the Central Andean Cordillera of Colombia at altitudes between 3000 and 1000 m above sea level. Interception amounts ranged from 11 to more than 20 per cent of the total rainfall and fell within the normal range of interception figures observed in natural tropical forests. Drop size spectra were established using the filter paper method; the drop size distributions of the open field rainfall were unimodal while the throughfall had bimodal distributions, with a higher percentage of the volume of rain falling as large drops. Disturbance of the natural forests, for example by logging activities or cattle grazing, will further increase the throughfall kinetic energy and may lead to higher splash erosion rates inside the forests than in the open field. The kinetic energy of the throughfall was higher than that of the open field rainfall (20-70 per cent), even after correcting for interception losses (4-30 per cent). Splash-cup experiments, conducted both in the field and in the laboratory, indicated that the kinetic energy is a good index of rainfall erosivity. Inside the forests the amounts of sand splashed from the splash-cups was, after correction for interception losses, 2-16 per cent higher than outside the forests.     

Use of ultrasonic treatment for extraction of humic acid with inorganic reagents from soil

The use of ultrasonic vibrations (1 hr) on the extraction of humic acids (HA) from a brown soil has been compared with the extraction by mechanical stirring (24 hr) with two extractants: 0.5 N and 0.1 M Na₄P₂O₇, followed by extraction with 0.5 N NaOH. In the pyrophosphate extraction, ultrasonic and mechanical treatments produced the same yield of HA. Further extraction with NaOH and mechanical stirring gave higher yields.The elemental composition of HA changed remarkably with both ultrasonic and mechanical systems. The HA extracted with ultrasonic treatment showed a higher ash content and a lower content of COOH and phenolic OH groups. These HA's showed higher optical density at 260 and 450 nm when pyrophosphate-extracted, and lower optical density when NaOH-extracted. Moreover the ultrasonic-treated HA in both extractants showed a lower E₄₀₀/E₆₀₀ ratio.Infrared examination confirmed the difference in chemical characteristics of extracted HA. The HA distribution in the different classes of nominal molecular weights by Sephadex gel filtration was influenced by both ultrasonic and mechanical systems, specially for molecular weights between 5000 and 150,000. It has been noted that the differences due to both systems are less marked than those caused by ssing different extractants.     

Evaluation of CF2Cl2 spectral parameters for atmospheric sensing

Laboratory infrared absorption spectral measurements of CF₂Cl₂ in the 10.8 m band have been performed. Doppler limited resolution has been achieved using semiconductor tunable lasers. The line strength and the self and pressure broadening rates have been measured for the 918.562 and 918.621 cm^–1 lines. The results are used for considerations on the application of high resolution spectroscopy to the measurement of atmospheric CF₂Cl₂.     

土壤激光诱导荧光遥感研究初探

对我国不同土壤的激光诱导荧光光谱的研究表明,在可见光波段的荧光峰一般在450nm左右,其相对荧光强度与土壤有机质含量、粘粒含量、水分含量以及土壤的化学组成密切相关。还表明.测试环境的差异,并不改变土壤的荧光光谱特征,仅影响它的相对荧光强度;不同的植被覆盖度会明显引起土壤荧光光谱的相应变化。这些结果展示出了激光荧光遥感技术应用于土壤类型和某些性状探测的可能性。应用红光波段是识别植被和土壤的最佳荧光波段。     

不同养分供应状况对水稻荧光光谱特征的影响及其在遥感应用上的意义

在不同的养分供应状况下,对水稻在几个生育期的荧光光谱特征的研究表明:氮素供应的减少会引起水稻叶片荧光光谱中蓝绿波段峰的强度在有效分蘖期时降低,无效分蘖期始升高,并使红波段峰的强度和特征峰之间的强度比值(如440nm/550nm)在各生育期均有所降低;利用水稻叶片荧光光谱特征的变化监测其养分供应状况是可能的;监测波段以400—800nm为宜,监测时期应为分蘖盛期一孕穗期。     

中国陆地背景和土壤光谱反射特性的地理分区的初步研究

通过对土壤光谱反射特性与土壤理化性状关系的研究,并根据我国土壤的分布规律,提出了以植被覆盖度和土壤光谱反射特性为基础的我国陆地背景地理分区的初步方案。该方案把我国划分为6个区和23个亚区。     

汞在金矿床中的分布及地质找矿意义

本文介绍了汞元素在各类金矿床(点)中的分布和汞的热释谱特征。在此基础上提出了汞法找金矿的重点应该是碳酸盐岩型金矿,有选择地兼顾其它类型的观点。