GIS支持下珠江三角洲城镇建筑覆盖变化遥感监测分析   总被引：15，自引：0，他引：15  

胡伟平  何建邦 《遥感学报》2003,7(3):201-206

从珠江三角洲区域总体出发，探讨大范围城镇建筑覆盖变化的遥感监测方法。分析了城镇建筑覆盖变化专题信息提取方法概况，比较了最大似然法、上下文分类法、人工神经网络三种分类方法的优缺点。借助GIS技术的术持，在计算机自动分类的基础上利用专家知识改进了分类结果。根据遥感监测结果，对1988—1998年间珠江三角洲城镇建筑覆盖变化特征进行了分析。  相似文献   

基于移动Agent的分布式地理信息查询   总被引：8，自引：0，他引：8  

关佶红  陈晓龙  陈俊鹏  周水庚 《武汉大学学报(信息科学版)》2003,28(1):39-44

提出了基于移动Agent的分布式地理信息查询的新思路，给出了构建基于移动Agent的分布式地理信息查询系统的方法，并利用移动Agent开发平台Aglets开发了一个分布式地理信息查询原型系统，实现了分布式地理信息的透明访问。  相似文献   

基于GPS基准站网的GPS测量   总被引：5，自引：0，他引：5  

胡丛玮  刘大杰 《现代测绘》2003,26(1):10-13

采用基于GPS基准网的GPS测量可以提高GPS测量的可靠性和准确性 ,可以消除和减小GPS测量观测值中与时间和空间相关的大气误差和轨道误差的影响 ,使中、长距离快速静态定位和RTK动态定位成为现实 ,还具有可直接得到WGS84Z坐标等优点。本文介绍基于GPS基准站网的GPS测量 ,简要地论述GPS虚拟参考站法VRS和区域改正数法FKP的原理、方法和特点 ,以及目前实施中存在的一些问题  相似文献   

路基施工沉降观测精度要求及数据处理     

蒋玉明  胡伍生  张志伟 《现代测绘》2003,26(1):17-18,23

本文通过对路基施工沉降观测的精度分析,提出了路基施工沉降观测的精度要求；根据路基施工沉降观测的特点，提出了相应的观测措施及数据处理方法。  相似文献   

利用MATLAB实现图像处理与分析   总被引：1，自引：0，他引：1  

董春来  王坚  胡建华 《现代测绘》2003,26(5):9-11

本文通过对图像的均衡操作、二值图像的处理、小波去噪等实例，介绍了MATLAB进行图像处理和分析的实用方法与技巧，它对各种软钉包、进行图像处理和分析等，提供了高效便捷的方法。  相似文献   

Mathematical Definitions of Operators for Cartographic Generalization     

王晓妮  张洁等 《地球空间信息科学学报》2003,6(1):70-73

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A biogenic-silica δO record of climatic change during the last glacial–interglacial transition in southwestern Alaska     

Feng Sheng Hu  Aldo Shemesh 《Quaternary Research》2003,59(3):379-385

Despite growing evidence for environmental oscillations during the last glacial–interglacial transition from high latitude, terrestrial sites of the North Pacific rim, oxygen-isotopic records of these oscillations remain sparse. The lack of data is due partially to the paucity of lakes that contain carbonate sediment suitable for oxygen-isotopic analysis. We report here the first record of oxygen-isotopic composition in diatom silica (δ¹⁸O_Si) from a lake in that region. δ¹⁸O_Si increases gradually from 19.0 to 23.5‰ between 12,340 and 11,000 ¹⁴C yr B.P., reflecting marked climatic warming at the end of the last glaciation. Around 11,000 ¹⁴C yr B.P., δ¹⁸O_Si decreases by 1.7‰, suggesting a temperature decrease of 3.5–8.9 °C at the onset of the Younger Dryas (YD) in southwestern Alaska. Climatic recovery began ca. 10,740 ¹⁴C yr B.P., as inferred from the increase of δ¹⁸O_Si to a maximum of 23.9‰ near the end of the YD. Our data reveal that a YD climatic reversal in southwestern coastal areas of Alaska occurred, but the YD climate did not return to full-glacial conditions.  相似文献   

Lipid distribution in a subtropical southern China stalagmite as a record of soil ecosystem response to paleoclimate change   总被引：3，自引：0，他引：3  

Shucheng Xie  Yi Yi  Junhua Huang  Chaoyong Hu  Yanjun Cai  Matthew Collins  Andy Baker 《Quaternary Research》2003,60(3):340-347

Lipid extracts from a 61.7-cm-long subtropical stalagmite in southern China, spanning the period of ca. 10,000–21,000 yr ago as constrained by U–Th dating, were analyzed using gas chromatography–mass spectrometry. The higher plants and microorganisms in the overlying soils contribute a proportion of n-alkanes identified in the stalagmite. The occurrence of LMW (lower molecular weight) n-alkanols and n-alkan-2-ones in the stalagmite was mainly related to the soil microorganisms. We suggest that HMW (higher molecular weight) n-alkanols and n-alkan-2-ones identified in the stalagmite originate from soil organics and reflect input from contemporary vegetation. Shifts in the ratio of LMW to HMW n-alkanols or n-alkan-2-ones indicative of the variation of soil ecosystems (e.g., microbial degradation of organic matter and/or the relative abundance of soil microorganisms to higher plants) are comparable with the subtropical alkenone-SST (sea surface temperature) record of the same period. The similar trends seen in the δ¹³C data and the lipid parameters in this stalagmite imply that the overlying soil ecosystem response to climate might be responsible for the variation of δ¹³C values.  相似文献   

Oxygen isotope salt effects at high pressure and high temperature and the calibration of oxygen isotope geothermometers     

Guixing Hu  Robert N. Clayton 《Geochimica et cosmochimica acta》2003,67(17):3227-3246

The influence of NaCl, CaCl₂, and dissolved minerals on the oxygen isotope fractionation in mineral-water systems at high pressure and high temperature was studied experimentally. The salt effects of NaCl (up to 37 molal) and 5-molal CaCl₂ on the oxygen isotope fractionation between quartz and water and between calcite and water were measured at 5 and 15 kbar at temperatures from 300 to 750°C. CaCl₂ has a larger influence than NaCl on the isotopic fractionation between quartz and water. Although NaCl systematically changes the isotopic fractionation between quartz and water, it has no influence on the isotopic fractionation between calcite and water. This difference in the apparent oxygen isotope salt effects of NaCl must relate to the use of different minerals as reference phases. The term oxygen isotope salt effect is expanded here to encompass the effects of dissolved minerals on the fractionations between minerals and aqueous fluids. The oxygen isotope salt effects of dissolved quartz, calcite, and phlogopite at 15 kbar and 750°C were measured in the three-phase systems quartz-calcite-water and phlogopite-calcite-water. Under these conditions, the oxygen isotope salt effects of the three dissolved minerals range from ∼0.7 to 2.1‰. In both three-phase hydrothermal systems, the equilibrium fractionation factors between the pairs of minerals are the same as those obtained by anhydrous direct exchange between each pair of minerals, proving that the use of carbonate as exchange medium provides correct isotopic fractionations for a mineral pair.When the oxygen isotope salt effects of two minerals are different, the use of water as an indirect exchange medium will give erroneous fractionations between the two minerals. The isotope salt effect of a dissolved mineral is also the main reason for the observation that the experimentally calibrated oxygen isotope fractionations between a mineral and water are systematically 1.5 to 2‰ more positive than the results of theoretical calculations. Dissolved minerals greatly affect the isotopic fractionation in mineral-water systems at high pressure and high temperature. If the presence of a solute changes the solubility of a mineral, the real oxygen isotope salt effect of the solute at high pressure and high temperature cannot be correctly derived by using the mineral as reference phase.  相似文献   

2002年7～8月海河流域面雨量预报的误差分析   总被引：2，自引：0，他引：2  

王新龙  胡欣  尤凤春 《气象》2003,29(6):41-45

对天津市气象台和河北省气象台在2002年7—8月的海河流域面雨量24h、48h预报进行了误差对比分析，列举了几种预报误差，并利用模糊数学中的综合评判法，计算了它们的模糊评分。结果表明：海河流域的面雨量预报有一定的可信度，把其作为水文模式的初值，有较高的利用价值；对于各气象台各自辖区内的预报，范围越小，预报越准确；在对面雨量预报效果的评估上，80％(或80)这一数值是客观、可信的。  相似文献