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Estimation of forest volumes by integrating Landsat TM imagery and forest inventory data

Science china(Technological Sciences) 2006年第z1期49卷 54-62页

作者： GU Huiyan, DAI Limin, WU Gang, XU Dong, WANG Shunzhong &WANG Hui Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016. china School of Forestry, Northeast Forestry University, Harbin 150040, china State Key Lab of Systems Ecology, Research center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, china Graduate University of Chinese Academy of Sciences, Beijing 100039, china Institute of Applied Ecology Chinese Academy of Sciences School of Forestry Northeast Forestry University State Key Lab of Systems Ecology Research Center for Eco-Environmental Sciences Chinese Academy of Sciences

Accurate information about forest volumes is essential for forest management planning. The survey interval of the Forest resource Inventory of china (FRIC) is too long to meet the demand for timely decision-making required for forest protection, management, and utilization. Analysis of {2. imagery provides good potential for more frequent reporting of forest parameters. In this study, we describe an application of the k-nearest neighbors (kNN) method to Landsat TM imagery for improving estimation of forest volumes. Several spectral features were tested and compared in forest volume estimations, including normalized difference vegetation index, environmental vegetation index, and the combination of the spectral features. The combined index resulted in the most accurate volume estimations. The kNN estimator and the combined index were then used in forest volume estimation. The estimation error (RMSE) of the total volume was44.2., much lower than those for Larix forest (the RMSE was 51.7%) and those for the Korean pine and broadleaved forests (the estimation errors were over 71.7% and 88.19%,respectively). This preliminary study demonstrates the potential of forest volume estimations with remote sensing data to provide useful information for forest management if only limited ground information is available.

关键词： forest inventory, landsat TM, k-nearest neighbors, spectral extraction.

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大西洋大眼金枪鱼渔场、资源及环境特征的研究

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海洋学报 2003年第S2期25卷 167-176页

作者：樊伟沈新强林明森东海水产研究所农业部海洋与河口渔业重点开放实验室上海200090 国家海洋局国家卫星海洋应用中心北京100081

根据2.02.7～12.对我国大西洋超低温深水延绳钓金枪鱼渔场(14°N～3°S,17°～40°W)调查获取的现场观测资料、结合收集到的历史渔获统计数据等,重点研究了大眼金枪鱼延绳钓作业渔场的环境特征及渔场空间分布,综合分析和讨论了大眼金... 详细信息

根据2.02.7～12.对我国大西洋超低温深水延绳钓金枪鱼渔场(14°N～3°S,17°～40°W)调查获取的现场观测资料、结合收集到的历史渔获统计数据等,重点研究了大眼金枪鱼延绳钓作业渔场的环境特征及渔场空间分布,综合分析和讨论了大眼金枪鱼的生物学特性与资源状况.结果表明,大西洋大眼金枪鱼延绳钓渔场主要分布在赤道两侧南北纬15°范围的热带海域,渔场分布具有显著的季节变化;渔场表层水温为2. 3～2. 9℃,最适表层水温为2.0}2.℃,其昼夜垂直移动与温跃层密切相关;渔场海水叶绿素a含量在0 02.0 33mg/m3;渔场多位于中等强度海流区,海流的变化可影响鱼群的位置移动.

关键词：大西洋延绳钓大眼金枪鱼

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application of Compass Ionospheric Model in GNSS Positioning

Application of Compass Ionospheric Model in GNSS Positioning

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第三届中国卫星导航学术年会

作者： Wu XiaoLi1Hu XiaoGong2..Wang Gang1*Zhong HuiJuan3&Tang ChengPan2.. Beijing Global Information center of application and Exploration, Beijing 100094,{2. 2. Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 2.0030,{2. 3.{2. Defense Science Technology Information center, Beijing 100142.{2.

As an important component of a GNSS navigation message, ionospheric delay model parameters are broadcasted for single-frequency users to improve their positioning accuracy. GPS provides daily Klobuchar ionospheric model parameters based on geomagnetic reference frame, while the regional satellite navigation system of Compass broadcasts an eight-parameter ionospheric model generated by processing real data from continuous monitoring stations, which is updated every 2.hours. To evaluate model performance, model predictions are compared against real ionosphere measurements, along with positioning accuracy comparisons. Real data analysis indicates that the Compass ionospheric model provides higher correction precision in middle-latitude regions, but relatively lower correction precision for low-latitude regions where ionosphere possesses much more variability. Thanks to the constellation design of Compass, ionospheric model errors for some receivers manifest a common bias for in-coming GNSS signals from different satellites. Consequently, ionospheric model errors are somehow translated into the receivers’ clock error estimation, while have less influence on the positioning. Given that the Chinese global navigation system will still rely on a domestic continuous monitoring network to provide global ionosphere correction service, the applicability of the ionospheric model in regions beyond china’s mainland is studied by applying the regional model to single-frequency positioning experiments of GPS. Real data analysis shows that in the northern hemisphere areas including Asia, Europe and North America, compared with the GPS single-frequency positioning using Klobuchar model for ionospheric delay corrections, the three-dimension position accuracy is improved by 7.8% 35.3% by using the Compass model. But the positioning accuracy in the southern hemisphere is degraded by 9.5%3.5% due to the lack of monitoring stations there.

关键词： ionospheric model regional satellite navigation system model error positioning error

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On Issues about the application of MIMO in Mobile Cellular Communications

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The Journal of china Universities of Posts and Telecommunications 2004年第Z1期11卷 50-54,61页

作者： REN Li-gang~1, SONG Mei~2. SONG Jun-de~2.1.china United Telecommunication Corporation, Beijing Branch 100038, P.R. china ***&CAD {2.,Beijing University of Posts and Telecommunications, Beijing 100876. P.R. china china United Telecommunication Corporation Beijing Branch 100038 P.R. China PCN&CAD center Beijing University of Posts and Telecommunications Beijing 100876 P.R. China

The convenience of mobile communications and the increasing demand for higher data transmitting rate have motivated people to explore more efficient methods of signal transmission because of the limited spectral resource. Multiple-Input and Multiple-Output (MIMO) is a high spectral efficient method and the theoretical capacity of a MIMO channel increases linearly with the number of transmitting/receiving antennas under the ideal conditions. We can adopt MIMO technology in the new generation of mobile cellular communication systems, which is IP based and requires high data rate to support multimedia services. Although much progress has been made in MIMO area recently, there are some problems in its practical application, especially in cellular application. In this paper we will analyze the channel model, the capacity and the technology of MIMO, and then we will focus on the issues of MIMO application in mobile cellular system by the Monte Carlo simulation and give the available solution schemes for the issues.

关键词： MIMO mobile communications co-channel interfe

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Research on Monitoring of Soil Humidity Based on AMSR-E data

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Meteorological and Environmental Research 2011年第10期2卷 5-7,16页

作者： LI Li1,KUANG Zhao-ming1,LUO Yong-ming1,HE Li1,ZENG Xing-ji2.1.National satellite Meteorological center,Remote Sensing {2. Test Base,Guangxi Meteorological and Disaster-Mitigation Research Institute,Nanning 53002.,china 2.Guangxi Meteorological Information center,Nanning 53002.,china

[Objective] The aim was to establish AMSR-E soil humidity monitoring model to realize the real-time monitoring of soil humidity.[Method] By dint of evaporation(small type) in Guangxi,daily precipitation,daily average maximum temperature,daily minimum relative humidity,≤ 5 mm precipitation day,as well as AMSR-E soil humidity data,with Stepwise regression method,soil humidity real-time monitoring was studied based on GIS technology,and monitoring result.[Result] The low soil humidity in Guangxi on September 2. in 2.05 mainly distributed in northeast Guangxi and central Guangxi,including Guilin City,Liuzhou City,Laibin City,Hezhou City,Guigang City,Nanning City,Hechi City and Baise City.[Conclusion] The AMSR-E statistical model based on meteorological observation data can be applied in real-time monitoring of soil humidity.

关键词： AMSR-E Evaporation Soil humidity GIS Drought china

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application of DEM overlaying technique in surface subsidence identification─a case study in Ruqigou coal mining area of Ningxia,china

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Journal of Geographical Sciences 1999年第1期9卷 43-50页

作者： CHEN Li-ding(Research center for Eco-Environmental Sciences, Chinese Academy of Sciences,Beijing 100085, china)

Subsidence occurred in many parts of the world. particularly in densely populated deltaic regions, causing extremely expensive damage. It can be resulted from natural causes. man-made induced causes, or other mixed causes. For identifying surface subsidence, many techniques have been employed, for example, geodetic monitoring, airborne laser subsidence measurement system,differential S.A.R., interferometry DGPS, and satellite radar measurements. However. all these methods require large time span and a large amount of field work. With the development of GIS techniques, identification of surface subsidence is becoming a relative easy problem. Ruqigou coal mining area was selected as a case study to identify the surface subsidence with DEM (digital elevation model) overlaying techniques. The result shows that DEM overlaying technique is a very useful method on surface subsidence identification. The accuracy of the results are largely dependent on the precision of the data-input.

关键词： surface subsidence Rubsidence coal mining area GIS DEM overlaying technique

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A double difference measuring method of pseudo-range precision using to the real environment

A double difference measuring method of pseudo-range precisi...

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第三届中国卫星导航学术年会

作者： Chunxia Li, Jinping Chen, Henglin Chu Beijing Global Information application and Development center, Beijing 100094,{2.

The pseudo-range measurement precision is an important index for evaluating the performance of a navigation receiver, and also one of the important factors for analyzing the receiver’s positioning precision. In the real environment the pseudo-range is varying and it is difficult to measure its precision, so usually the pseudo-range precision is measured on a laboratory simulation condition. But this measuring method could not truly reflect the pseudo-range precision in the real environment. In this paper, a measuring method of pseudo-range precision using to the real environment, namely receiver and satellite double difference method, is presented. Its theory basis is given by deducing its mathematic model, and then experiment is made on pseudo-range precision measuring with this method. The results of the experiment show that when the receiver is stationary, this method can accurately measure the precision of its observation pseudo-range to a static satellite, and can accurately measure the precision of its observation pseu-do-range to a motional satellite by controlling the observation time. Finally the obtained pseudo-range precisions are used to compare the precisions of two posi-tioning modes, and the comparison relationship of the precisions of the two posi-tioning modes observed in the real data is intuitively revealed.

关键词： double difference pseudo-range measure precision real environment positioning precision

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面向测控的运载火箭仿真设计与实现

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系统仿真学报 2004年第11期16卷 2507-2510页

作者：杨永安冯祖仁杜小宁王波张宏伟西安交通大学西安710049 西安卫星测控中心西安710043

随着航天测控系统任务日益增多、周期缩短、技术要求提高等现实,如何确保每次实战任务地面火箭遥测设备和测控软件的正常运行,火箭外测和遥测数据处理快速准确,对航天测控系统而言尤为重要和迫切,而构建面向测控的运载火箭仿真是解决此... 详细信息

随着航天测控系统任务日益增多、周期缩短、技术要求提高等现实,如何确保每次实战任务地面火箭遥测设备和测控软件的正常运行,火箭外测和遥测数据处理快速准确,对航天测控系统而言尤为重要和迫切,而构建面向测控的运载火箭仿真是解决此问题的重要手段之一。本文首先介绍了面向测控的运载火箭仿真的功能需求和系统组成;其次提出了面向测控的运载火箭仿真系统设计方案以及测试方法;最后总结了面向测控的运载火箭仿真的应用情况和发展方向。

关键词：面向对象航天测控系统仿真技术运载火箭

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Evaluation of Ionospheric Correction Models in the Middle Latitude

Evaluation of Ionospheric Correction Models in the Middle La...

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第三届中国卫星导航学术年会

作者： BI JiaHong,TANG Yun,WU XiaoLi,CAO JiDong,MA MinBeijing Global Information application and Development center,Beijing 100094,{2.

Ionospheric error is one of the main error sources in satellite navigation systems and ionospheric error correction precision directly affects the positioning *** influence of ionosphere on pseudorange and phase measurements is analyzed in this *** the commonly used ionospheric delay correction methods for different users in the application are then ***,the characteristics of different ionospheric models broadcasted by different satellite navigation systems are then *** using real measurements,the ionospheric model of COMPASS in mid-latitude is compared with dual-frequency ionospheric correction values and the GIM ionospheric correction *** data analysis shows that Compass 1 and Compass 2.models accord with the GIM model of CODE *** results of one day data indicates that RMS of Compass model is within 3 meters.

关键词： Ionosphere correction models correction error Klobuchar

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Secular changes in differential code bias of COMPASS system

Secular changes in differential code bias of COMPASS system

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第三届中国卫星导航学术年会

作者： XING Nan1,2.*WU Xiaoli3HU Xiaogong1SU Ranran31 Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 2.0030, china 2.Graduate University of Chinese Academy of Sciences, Beijing 100049, china 3 Beijing Global Information {2. of application and Exploitation, Beijing 100094, china

DCB （Differential Code Bias）, named TGD （Timing Group Delay） for satellite and IFB （Inter-Frequency Bias） for receiver, is a crucial parameter in COMPASS system, which is needed in satellite clock correction and ionospheric delay modeling. Though DCB parameters were measured in laboratory initially, it may change with working environment as well as with time elapsed, necessitating DCB estimation for the deployed satellites and receivers. DCB estimates can be obtained by combining COMPASS data in 3 frequencies and accurate ionospheric TEC （Total Electron Content） models （e.g. Global Ionosphere Model, GIM from International GNSS Service）. However, TEC model errors as revealed by discrepancies with GPS observations would translate into and contaminate DCB estimates. This study concludes that the error GIM brought into TGD is under 1ns that is equivalent to a positioning error of 0.18m, an ionospheric time delay correction error of 0.4-0.7m and TEC models error of 3TECU. Analysis of COMPASS data for 2.0 days in 2.11 shows a secular change in TGDs with amplitude of about 1.5ns for GEO satellites and 4ns for IGSO satellites respectively and in IFBs with amplitude of 3ns. The DCB time series could be well fitted by a second-degree polynomial with residuals of 0.4-0.6.s for TGDs and 0.6.0.9ns for IFBs, based on which the TGD could be predicted with accuracy of 0.5ns for GEO satellites and 0.5-1ns for IGSO satellites respectively.

关键词： COMPASS DCB TGD

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