用L-曲线法确定半参数模型中的平滑因子

提出了一种新的方法——L-曲线法确定平滑因子。通过确定合适的平滑因子，更好地控制了残差部分V^TPV与光滑度部分S^TRS之间的平衡，得到了更准确的参数估值。通过算例，将基于L-曲线法确定平滑因子的半参数模型解算方法和其他方法进行了比较。结果表明，用L-曲线法确定平滑因子后，提高了半参数模型计算结果的精度，可以更好地将观测值中的系统误差分离出来。     

建筑物沉降规律的综合时序分析

建筑物的沉降监测数据序列具有趋势变化和随机变化的特点，本文针对两种变化项的特点分别建立相应的数学模型，再将其组合起来建立综合数学模型，从总体上把握沉降数据序列的变化规律。实例计算分析表明，此方法具有较高的拟合精度和预测能力，具有一定的应用参考价值。     

基于Matlab的水准点稳定性分析

通过使用Matlab功能强大的数学软件，应用于测量工程的数据处理。具体解决变形监测中水准点是否稳定的判定问题。并通过计算实例说明其可行性和优越性。     

基于物方影像匹配和概率松弛的断面自动提取

提出了基于物方影像匹配的断面提取,为了提高匹配的可靠性,引入了概率松弛法,最终获得了高精度的断面.     

基于OpenGIS规范的地理信息系统组件的内核及功能设计

提出了符合OpenGIS规范的二维地理信息系统组件软件MapManager的设计思想 ,介绍了MapManager的设计过程 ,并对其不足和进一步研究方向进行了讨论。     

基于J2EE的移动定位服务研究

阐述了基于J2EE的移动定位服务 (MLS)的体系结构 ,介绍了适于MLS的GIS应用服务器和信息设备地图可视化表达的关键技术 ,给出了GeoSurf的WAP和J2ME的两种解决方案 ,并阐述了其应用前景     

航天GPS接收机设计

航天GPS接收机为航天器提供航迹、姿态、时问和相对距离等导航信息，提高航天嚣运行的自主性。文中介绍了清华宇航中。航天GPS接收的硬件和软件设计，给出测试结果和分析。     

用L-曲线法确定岭估计中的岭参数

运用L 曲线法来确定岭估计中的岭参数 ,推导了用L 曲线法确定岭参数的基本公式 ,在此基础上实现了其算法 ,并用两个算例 ,比较了新方法和以往方法。结果表明 ,L 曲线法不仅容易收敛 ,而且其计算结果的精度较高     

Self-affinity dimensions of topography and its implications in morphotectonics: an example from Taiwan

This paper discusses the self-affinity dimensions of landscape surfaces at a short-range scale and the link to morphotectonic features of the young orogenic belts of Taiwan. The variogram method is adopted to estimate such parameters as the fractal dimension (D), the ordinate-intercept (γ) and the range (R) from data subsets of the digital elevation model (DEM) in a moving-window operation. The fractal morphology expressed by D and γ is found to be useful in defining geomorphic provinces that are related to tectonic features. The mountainous terrain is characterized by high gamma values and low fractal dimensions in contrast to the coastal plains where low gamma values and high fractal dimensions are found. A zone, defined by the fractal parameters (2.4<D<2.6 and 0<γ<2.4), is found to coincide with the most tectonically active zone of Taiwan. Active faults often occur at the boundary between landscapes with contrasting fractal patterns. In the flat lowlands along the western coast, the fractal morphology displays a west-facing amphitheatric pattern, which may be related to the indentation of the pre-Miocene Peikang Basement High. The fractal morphology may reflect some subtle changes in surface textures of a landscape sculpted by surface processes, which in turn are influenced by tectonic activities. The surface roughening and diffusive smoothing may concur to shape the landscape surface at the short ranges we discuss in this study.     

A Local Example of Land‐Use Change: Southern Illinois—1807, 1938, and 1993*

This article provides an analysis of a wetland site in southern Illinois from presettlement to the present. The study area is part of the Cache River‐Cypress Creek Wetland, which has international importance, as recognized by the Ramsar Convention on Wetlands. Land‐cover data for 1807, 1938, and 1993 were created and analyzed with a geographic information system (GIS). Land‐use change by topographic setting (uplands, transitional, and bottomlands) and soil productivity was quantified and studied. Interviews with local experts informed this analysis. Results illustrate the complexity of environmental change and its driving forces. First, notable forest and swamp acreage was converted to cropland between 1807 and 1938 and, to a lesser degree, from 1938 to 1993. Second, there were land‐use variations by topographic region. Between 1807 and 1938, the largest transformation occurred in the uplands, with substantial acreage converted from forest to cropland. Between 1938 and 1993, however, agriculture decreased in the upland areas as hilly areas reverted to forest cover. At the same time, agriculture expanded in the bottomlands as this land was drained for farming. Third, there are interesting patterns within these categories of land‐use change, as soil productivity is an indicator of what lands were taken out of cropland and converted back to grassland and forest.