Discrete Modeling and Suggested Measurement of Heat Transfer in Gas-Solids Flows

This article presents a two-dimensional transient model for gas-solids flow and heat transfer through pipes using the coupled Computational Fluid Dynamics and Discrete Element Method approach. Numerical simulations have been conducted to examine the modification of fluid thermal structure due to the presence of particles in a pneumatic transport pipeline. Modeled results have demonstrated the key role of transversal motion of rebounding particles in the pipe cross section in altering fluid temperature. Further implementation of this modeling technique in air-drying processes is discussed and possible experimental methods for the measurement of in situ particle and fluid motion and temperature profile are cited.     

An empirical InSAR-optical fusion approach to mapping vegetation canopy height

Exploiting synergies afforded by a host of recently available national-scale data sets derived from interferometric synthetic aperture radar (InSAR) and passive optical remote sensing, this paper describes the development of a novel empirical approach for the provision of regional- to continental-scale estimates of vegetation canopy height. Supported by data from the 2000 Shuttle Radar Topography Mission (SRTM), the National Elevation Dataset (NED), the LANDFIRE project, and the National Land Cover Database (NLCD) 2001, this paper describes a data fusion and modeling strategy for developing the first-ever high-resolution map of canopy height for the conterminous U.S. The approach was tested as part of a prototype study spanning some 62,000 km² in central Utah (NLCD mapping zone 16). A mapping strategy based on object-oriented image analysis and tree-based regression techniques is employed. Empirical model development is driven by a database of height metrics obtained from an extensive field plot network administered by the USDA Forest Service-Forest Inventory and Analysis (FIA) program. Based on data from 508 FIA field plots, an average absolute height error of 2.1 m (r = 0.88) was achieved for the prototype mapping zone.     

基于HJ-1B卫星遥感数据的水稻识别技术研究

为快速、准确地在遥感图像上识别水稻作物的信息,满足县级尺度水稻遥感监测的需要,以野外实地调查资料、1∶5万地形图数据为辅助,通过光谱分析法,分析研究HJ-1B星CCD数据的水稻作物的光谱反射特性,建立水稻作物遥感信息识别模型。采用决策树分类方法提取水稻作物信息,并将该技术方法应用于广西宾阳县水稻作物信息提取研究。采用实测样地数据,利用混淆矩阵进行精度评价验证,总精度为94.9%,Kappa系数为0.8533。研究表明,该水稻作物的识别技术,可以为了解我国水稻种植情况,进行水稻长势监测和产量估测提供技术参考。     

利用QAR和DEM的机载气象雷达地杂波仿真方法

地杂波是降低机载气象雷达性能的一个关键因素。利用数字高程模型（Digital elevation model,DEM）精确计算不同地形的电磁散射时,本文提出了将经纬度变化量转换成距离变化量的方法,简化计算,并修正了俯角和擦地角计算。然后根据气象雷达方程建模地杂波,按照WXR-2100的实际参数设置雷达参数,结合快速存取记录器（Quick access recorder,QAR）反演的航班飞行参数,分别高保真地仿真了起飞和巡航两个阶段机载气象雷达不同工作模式下的杂波图,反映了实际的运行情况,最后建立了杂波图数据库。     

Forest biomass mapping from lidar and radar synergies

The use of lidar and radar instruments to measure forest structure attributes such as height and biomass at global scales is being considered for a future Earth Observation satellite mission, DESDynI (Deformation, Ecosystem Structure, and Dynamics of Ice). Large footprint lidar makes a direct measurement of the heights of scatterers in the illuminated footprint and can yield accurate information about the vertical profile of the canopy within lidar footprint samples. Synthetic Aperture Radar (SAR) is known to sense the canopy volume, especially at longer wavelengths and provides image data. Methods for biomass mapping by a combination of lidar sampling and radar mapping need to be developed.In this study, several issues in this respect were investigated using aircraft borne lidar and SAR data in Howland, Maine, USA. The stepwise regression selected the height indices rh50 and rh75 of the Laser Vegetation Imaging Sensor (LVIS) data for predicting field measured biomass with a R² of 0.71 and RMSE of 31.33 Mg/ha. The above-ground biomass map generated from this regression model was considered to represent the true biomass of the area and was used as a reference map since no better biomass map exists for the area. Random samples were taken from the biomass map and the correlation between the sampled biomass and co-located SAR signature was studied. The best models were used to extend the biomass from lidar samples into all forested areas in the study area, which mimics a procedure that could be used for the future DESDYnI mission. It was found that depending on the data types used (quad-pol or dual-pol) the SAR data can predict the lidar biomass samples with R² of 0.63-0.71, RMSE of 32.0-28.2 Mg/ha up to biomass levels of 200-250 Mg/ha. The mean biomass of the study area calculated from the biomass maps generated by lidar-SAR synergy was within 10% of the reference biomass map derived from LVIS data. The results from this study are preliminary, but do show the potential of the combined use of lidar samples and radar imagery for forest biomass mapping. Various issues regarding lidar/radar data synergies for biomass mapping are discussed in the paper.     

Near-global validation of the SRTM DEM using satellite radar altimetry

This paper reports the results of a near-global validation of the SRTM DEM dataset, using a unique database of completely independent height measurements derived from satellite altimeter echoes, primarily gathered by ERS-1. These heights are obtained using a rule-based expert system which identifies each echo as 1 of 11 different characteristic shapes, and selects the optimal retracking algorithm to obtain best range to surface. The results of this comparison, which includes over 54 million altimeter derived heights, show generally very good agreement with the SRTM data, with global statistics for mean difference of 3 m and a standard deviation of 16 m. Quantitative validation results are given for each continent and are summarised here.

	Mean difference (m)	Standard deviation of differences (m)
Africa	1.86	15.62
Australia	1.09	11.49
Eurasia	2.54	16.09
North America	3.15	15.18
South America	12.22	18.51
Global	3.60	16.16

Full-size table

     

基于SRTMv4的异龙湖流域地形因子提取

以最新SRTMv4版DEM作为基础数据,选择异龙湖流域为研究区域,利用ArcGIS 10平台中的水文分析扩展模块提取异龙湖流域的流域边界和流域水文特征两方面的流域地形因子。根据提取结果与获取到的实测数据进行有效性检验:①与实际调查数据的水系网和1∶5万水系图对照比较,发现基于SRTM DEM所提取出的流域地形因子等信息是合理有效的。②与1∶5万DEM所提取流域水网进行对比发现基于SRTM DEM所提取的数据精度较为满意,在相同河网密度情况下,基于SRTM的DEM与1∶5万DEM的水网细节表现高度一致,具有可靠性。     

DEM与空间叠加分析在土地定量评价中的研究

以湖北省建始县为例，研究了海拔、坡度和坡向与该区农业生产条件的关系，建立了土地适宜性评价模型。在MapGIS支持下，该文综合应用数字高程模型（DEM）及空间叠加分析技术实现了该模型在土地适宜性评价中的应用。实践表明，该数字化定量评价方法所得的结果与实际情况相符，具有高效、准确和可视化的特点，可为政府决策提供支持。     

地形三维可视化的实现与应用

文中讨论了地形三维可视化的原理，详细介绍了高级编程语言与OpenGL结合开发环境下的地形三维可视化的计算机实现过程。在此基础之上，讨论了基于GRID DEM的应用分析功能的实现,包括等高线、坡度图、通视分析以及淹没分析。为三维地形可视化的实施提出了有效的方案。