基于方差分量估计的拟合推估及其在GIS误差纠正的应用

拟合推估解算必须首先求得信号向量的方差协方差矩阵,该协方差矩阵一般通过选定的协方差函数,并通过已测点数据进行拟合得到。显然观测噪声的先验方差协方差阵与拟合得到的随机信号的方差协方差矩阵必须相互协调,即观测噪声向量和信号向量的权矩阵所对应的方差因子应该一致,否则将对固定效应和随机效应参数的估计带来系统性的影响。应用方差分量估计来协调拟合推估模型中观测噪声和信号向量的随机模型,并分别从极大似然估计、MINQUE估计、赫尔默特方差分量估计三方面构建了拟合推估模型的方差分量解,最后利用新提出的理论与方法,对一幅实际的扫描地形图进行误差纠正,结果表明基于方差分量估计的拟合推估法能够提高扫描地形图的精度。     

Where can pixel counting area estimates meet user-defined accuracy requirements?

Pixel counting is probably the most popular way to estimate class areas from satellite-derived maps. It involves determining the number of pixels allocated to a specific thematic class and multiplying it by the pixel area. In the presence of asymmetric classification errors, the pixel counting estimator is biased. The overarching objective of this article is to define the applicability conditions of pixel counting so that the estimates are below a user-defined accuracy target. By reasoning in terms of landscape fragmentation and spatial resolution, the proposed framework decouples the resolution bias and the classifier bias from the overall classification bias. The consequence is that prior to any classification, part of the tolerated bias is already committed due to the choice of the spatial resolution of the imagery. How much classification bias is affordable depends on the joint interaction of spatial resolution and fragmentation. The method was implemented over South Africa for cropland mapping, demonstrating its operational applicability. Particular attention was paid to modeling a realistic sensor's spatial response by explicitly accounting for the effect of its point spread function. The diagnostic capabilities offered by this framework have multiple potential domains of application such as guiding users in their choice of imagery and providing guidelines for space agencies to elaborate the design specifications of future instruments.     

应用累积法建立产量预测模式

在产量预测模式研究中常用的回归参数估计方法是最小二乘法,但该方法以某些统计假设为前提,计算也比较复杂,特别是在应用短序列资料建模时会受到很大的限制。而累积法是对原始数据序列按一定的规律进行相应叠加,用之建立线性模型,其估计量具有无偏、线性、有效、唯一等特点,估计效果与最小二乘法相同且计算过程更简便。因此,应用累积法,建立了安徽省桐城市一季稻产量预测模式,并介绍了累积法的建模过程和误差分析方法。应用累积法建立的桐城一季稻产量预测模式的历史回代误差率平均为3.90%,2011、2012两年试报准确率分别为95.7%和97.0%,与最小二乘法建立的预测模式误差率相近且略小,其估计精度完全符合业务要求。投入业务使用后,2013、2014年实际预报准确率分别为92.9%、98.5%。累积法的不足之处是随着自变量个数和样本容量的增大,正规方程组系数矩阵的病态性也会随之加剧,从而影响参数估计的精度。     

开发区居住空间特征及其形成机制——对北京经济技术开发区的调查

利用北京经济技术开发区的第一手问卷调查数据,研究开发区居住空间特征及其形成机制。研究表明：开发区居住人口收入和受教育程度相对较高,外来人口已成为开发区后期居住人口增长的主要动力来源;开发区的住房类型构成呈现多样化特点,政策和住房户型原因是影响住宅分化的重要因素;开发区在收入和社会阶层方面存在居住分化现象,具体表现为高收入和低社会阶层两级分化的空间隔离;作为新兴的郊区社区,开发区居民维权意识强烈,但社区联系较弱;上班通勤距离仍是影响居民居住地选择的最重要因素,改善居住环境、对优质教育资源的追求也是极重要的因素。最后,从居民、开发商、地方政府、企业、母城及周边区域等多元主体共同作用的角度探讨了开发区居住空间的形成机制。当前,国内开发区大多面临从“产业功能地域”向综合型的“城市化功能地域”转型,但开发区既是“产业集聚区”又被作为“卧城”的复杂状况,也带来其居住空间特征及形成机制的复杂性。研究成果对于丰富城市居住空间理论有重要意义。     

多种顾及先验信息的平差及其比较

在阐述各种顾及先验信息平差方法的基本概念及性质的基础上，着重分析了它们之间的关系与区别，从而为这些平差理论的进一步发展与应用奠定了基础。     

强震振动的共振效应与昆明市高层建筑震害

本文根据对昆明的5层楼房和昆明市工人文化宫18层建筑的脉动观测,结合作者对昆明市几种地基土的脉动观测研究,提出了强震的卓越周期昆明地基土和建筑物的固有周期之间与震害的关系,可供有关部门在城市规划建设和编制抗震防灾规划中参考。     

Inverse methods for subsurface flow: A critical review of stochastic techniques

The development of stochastic methods for groundwater flow representation has undergone enormous expansion in recent years. The calibration of groundwater models, the inverse problem, has lately received comparable attention especially and almost exclusively from the stochastic perspective. In this review we trace the evolution of the methods to date with a specific view toward identifying the most important issues involved in the usefulness of the approaches. The methods are critiqued regarding practical usefulness, and future directions for requisite study are discussed.     

Accurate Acoustic Signal Parameter Estimation for Marine Geodesy Surveys

Acoustic signal parameter estimation is important for diverse marine geodesy surveys and several other applications. However, the received signal from a far-field target characterized by planar wavefront propagation is frequently affected by strong nearby interfering signals. Their presence deteriorates the performance of direction-of-arrival (DOA) estimation for far-field target. In order to enhance the reception of signal from far-field target, the near-field/far-field (NFFF) beamformer is proposed. Such a beamformer optimizes beam pattern for far-field detection by maximizing beamformer output in the direction of the far-field target with the imposed condition to eliminate interfering signals generated in near-field locations. As the interference suppression only occurs at the position of near-field interference, a possible blind zone for far-field detection in conventional methods is not created. The NFFF beamformer is applicable for coherent signals and the scenario with multi interferences. For stationary situation where interferers locations are fixed, the NFFF beamformer computations do not require time updates with associated computational load. Furthermore the proposed method can be extended to several new situations such as acoustic monitoring performed from a stationary platform subjected to water currents, waves, winds and other variables, all of them generating nearby interferences and also to different array configurations including 2D and 3D arrays.