An update on the IEM surface backscattering model

The integral equation approach to modeling scattering from rough surfaces was introduced in 1992. At that time, it was noted that there was a need to find a transition reflection coefficient that could change its argument from the incident angle to the specular angle as frequency or roughness scale got large. One such reflection coefficient was published in 2001. In this letter, we would like to include this reflection coefficient in the integral equation model to interpret several multifrequency backscattering measurements from surfaces with surface parameters defined by the investigators who acquired the data.     

Tile‐based polygon overlay of vector data in a virtual globe

The demand for analysis of large‐scale data has increased with increased access to spatial vector data. Polygon overlay of vector data in a virtual globe requires proprietary data structures and proprietary analysis algorithms. A vector data structure is designed for rapid polygon overlay in a virtual globe by recording the metadata of the triangles (TriMeta) that constitute polygons. A polygon overlay algorithm is proposed based on this data structure. The overlay of two complex GIS polygons is transformed into the intersection computation of their 3D triangular presentations. The intersection computation of two sets of triangles is reduced considerably by utilizing TriMeta to filter out the disjoint triangle pairs and rapidly identify the contained triangle. The new method improves the overlay efficiency in a virtual globe because the amount of computation required to calculate the intersections of two large polygons and drape the intersections onto a terrain surface is reduced.     

Geospatial technologies for Chang’e-3 and Chang’e-4 lunar rover missions

ABSTRACT

This paper presents a brief overview of the geospatial technologies developed and applied in Chang’e-3 and Chang’e-4 lunar rover missions. Photogrammetric mapping techniques were used to produce topographic products of the landing site with meter level resolution using orbital images before landing, and to produce centimeter-resolution topographic products in near real-time after landing. Visual positioning techniques were used to determine the locations of the two landers using descent images and orbital basemaps immediately after landing. During surface operations, visual-positioning-based rover localization was performed routinely at each waypoint using Navcam images. The topographic analysis and rover localization results directly supported waypoint-to-waypoint path planning, science target selection and scientific investigations. A GIS-based digital cartography system was also developed to support rover teleoperation.     

基于遥感技术的近30年中亚地区主要湖泊变化

在全球气候变暖的背景下,研究中亚干旱半干旱地区主要湖泊的变化不仅对内陆水资源管理和可持续发展有着重要意义,也为进一步研究湖泊变化对气候变化和人类活动的响应提供基础。获取1978年MSS、1989年TM、1998年TM及2010年ETM的同季相4期遥感图像数据,通过人工解译提取中亚地区7个湖泊信息,获得近30 a的湖泊面积变化;利用T/P和Envisat雷达高度计提取1992—2012年的湖泊水位信息;基于湖泊面积和水位的时空变化特征分析了湖泊变化的影响因素。结果表明:近30 a来,由于湖泊类型的不同,除萨雷卡梅什湖外的其他6个湖泊均出现不同程度的面积缩减;其中,平原尾闾湖面积变化最显著,高山封闭湖相对平稳,吞吐湖泊的面积变化相对复杂;湖泊的水位变化模式因流域和湖泊类型而异;高山封闭湖泊受气候的影响较大,而吞吐湖泊受人为因素影响显著。     

利用射线追踪法分析三种典型对流层映射函数在中国区域的精度

基于中国区域内8个气象站点2012年全年的探空数据,采用射线追踪法计算了各个站天顶方向至4°高度角区间内18个方向的对流层流体静力学和非流体静力学延迟量,将天顶延迟通过NMF、GMF和VMF1三种映射函数投影到各个高度角方向,与射线追踪法得出的延迟量进行比较,结果显示:①NMF有明显的季节性偏差,且精度与纬度存在强相关性;②VMF1的精度最高、稳定性最好,但在武汉、长沙等站点存在一定的季节性偏差;③GMF的精度介于NMF和VMF1之间。     

基于OGC标准的基础地理数据集群服务设计

现代三维数字地球已成为GIS技术应用的常用前端展现平台,采用的海量高分辨率遥感影像、分层地名数据和DEM数据的数字地球能否提供高效服务成为制约数字地球框架实用性的关键因素。本文对目前流行的由World Wind项目组基于OGC标准实现的WMS服务及通过Geo Server项目实现的地名服务建立基础地理集群服务的方法进行了研究,同时还针对不同分辨率、不同存储模式的的影像数据服务效率给出了实际分析测试结果。     

Degradation of native wheat straw lignin by Streptomyces viridosporus T7A

Lignin is one of the major contributing factors toward the recalcitrance of lignocellulosic biomass. Understanding the process of lignin degradation in natural biological processes will provide useful information to develop novel biomass conversion technologies. Functional group changes in the lignin entities during the process may contribute to the cellulose degradation (utilization) by the microorganisms. In this study, compositional and advanced Fourier transform infrared, pyrolysis gas chromatography/mass spectrometry and ¹³C cross polarization/magic angle spinning nuclear magnetic resonance analysis were performed to explore the mechanism of biodegradation of wheat straw by Streptomyces viridosporus T7A. The results indicated that S. viridosporus T7A removed lignin and hemicelluloses as indicated by the increased carbohydrate/lignin ratio. Significant modification of carbonyl and methoxyl groups in the complex lignin structure was also evident. Most importantly, the quantitative results showed that lignin degradation was featured by deduction of guaiacyl unit. The results provide new insight for understanding lignin degradation by bacteria.     

广西平桂地区观赏石简介

广西平桂地区观赏石资源丰富。本文简介该区观赏石的常见品种及其特点、成因类型、分布规律、质量评价及开发前景。     

SUSTAINABLE DEVELOPMENT FACING CHALLENGESIN 21ST CENTURY

ISUSTAINABLE DEVELOPMENT IS UNDER UN－guiding human forward．he author pointed out manyCEASINGCHALLENGES times that sustainable developmentwas a correctstrategic selectlonforhumanfuture and It representedaThe Zlst Century has come，people have many newdevelopmentoutlook，strategic vie呷olntandvalueforecasts and long for a wonde山lprospect．The 21st（CHEN，1997；200a；200b）．Century lsa bio－sclentmc era，an economic global－The authoralso pointed out th…     

Precipitation variability during the past 400?years in the Xiaolong Mountain (central China) inferred from tree rings

We developed the first tree-ring chronology, based on 73 cores from 29 Pinus tabulaeformis trees, for the Xiaolong Mountain area of central China, a region at the boundary of the Asian summer monsoon. This chronology exhibits significant (at 0.01 level) positive correlations with precipitation in May and June, and negative correlations with temperature in May, June and July. Highest linear correlation is observed between tree growth and the seasonalized (April–July) precipitation, suggesting that tree rings tend to integrate the monthly precipitation signals. Accordingly, the April–July total precipitation was reconstructed back to 1629 using these tree rings, explaining 44.7?% of the instrumental variance. A severe drought occurred in the area during the 1630s–1640s, which may be related to the weakened Asian summer monsoon caused by a low land-sea thermal gradient. The dry epoch during the 1920s–1930s and since the late 1970s may be explained by the strengthened Hadley circulation in a warmer climate. The dry (wet) epochs of the 1920s–1930s (the 1750s and 1950s) occurred during the warm (cold) phases of the El Ni?o-Southern Oscillation and the Pacific Decadal Oscillation that are often associated with weakened (strengthened) East Asian summer monsoon. These relationships indicate significant teleconnections operating over the past centuries in central China related to large-scale synoptic features.