利用地面激光扫描数据进行建筑物变化检测

利用地面激光扫描仪具有的数据获取速度快、精度高、实时性强、能全天候工作等优点,在快速获取三维点云的基础上,通过点云自动拼接、Hausdorff距离检测不同时期建筑物的三维模型变化,并改进了检测算法,提高了算法的执行效率。通过拟合平面构建Delaunay三角网求解变化区域的面积来评估灾害对建筑物的破坏程度,从而为灾害应急响应以及保险理赔等提供了可靠的决策依据。     

Monitoring global land surface drought based on a hybrid evapotranspiration model

The latent heat of evapotranspiration (ET) plays an important role in the assessment of drought severity as one sensitive indicator of land drought status. A simple and accurate method of estimating global ET for the monitoring of global land surface droughts from remote sensing data is essential. The objective of this research is to develop a hybrid ET model by introducing empirical coefficients based on a simple linear two-source land ET model, and to then use this model to calculate the Evaporative Drought Index (EDI) based on the actual estimated ET and the potential ET in order to characterize global surface drought conditions. This is done using the Global Energy and Water Cycle Experiment (GEWEX) Surface Radiation Budget (SRB) products, AVHRR-NDVI products from the Global Inventory Modeling and Mapping Studies (GIMMS) group, and National Centers for Environmental Prediction Reanalysis-2 (NCEP-2) datasets. We randomly divided 22 flux towers into two groups and performed a series of cross-validations using ground measurements collected from the corresponding flux towers. The validation results from the second group of flux towers using the data from the first group for calibration show that the daily bias varies from −6.72 W/m² to 12.95 W/m² and the average monthly bias is −1.73 W/m². Similarly, the validation results of the first group of flux towers using data from second group for calibration show that the daily bias varies from −12.91 W/m² to 10.26 W/m² and the average monthly bias is −3.59 W/m². To evaluate the reliability of the hybrid ET model on a global scale, we compared the estimated ET from the GEWEX, AVHRR-GIMMS-NDVI, and NECP-2 datasets with the latent heat flux from the Global Soil Wetness Project-2 (GSWP-2) datasets. We found both of them to be in good agreement, which further supports the validity of our model's global ET estimation. Significantly, the patterns of monthly EDI anomalies have a good spatial and temporal correlation with the Palmer Drought Severity Index (PDSI) anomalies from January 1984 to December 2002, which indicates that the method can be used to accurately monitor long-term global land surface drought.     

基于ObjectARX技术的AutoCAD数据格式转换

概要介绍了ObjectARX开发环境以及ARX应用程序,重点论述了如何在ObjectARX开发环境下,编写ARX应用程序,实现对AutoCAD数据库的访问,及对AutoCAD数据进行提取和格式转换的方法,给出了具体的实现思路和实现的代码细节。     

地图制图专家知识对地理信息符号化过程的控制

针对纸质地图数字化得到地理信息(空间数据)的过程中存在地图信息损失的问题,阐述了产生这种损失的原因。数字化后得到的地理信息是各种GIS应用系统的重要数据源,在GIS应用中需要把这些地理信息重新再现成地图。为了得到较好的地图显示效果,有必要将数字化后损失的地图信息在从地理数据到地图符号化的过程中进行补偿。论述了在符号化过程中如何充分利用地图制图专家的多年知识和经验,将用自然语言表达的不确定性的专家知识形式化,以此来控制整个符号化的过程,达到改善地图显示效果的目的。     

南京长江三桥钢索塔拼装测量控制网的建立

南京长江三桥是我国首座主塔采用钢结构形式的特大型斜拉桥。根据钢索塔拼装测量的精度要求,介绍了该桥首级控制网的概况,对钢索塔架设专用控制网的网形选择、方案设计、观测方法和数据处理进行了探讨。实践证明,所采取的专用控制网布设方法和测量方案是合理的,对今后类似工程具有借鉴意义。     

GPS中CCD技术的原理与应用

码／载波相位扩散技术可使单频ＧＰＳ接收机的测程从２０ｋｍ急剧扩大到４００ｋｍ。本文叙述其简单原理与实际应用。     

一种新的二进制地图矢量文件格式设计

比较了二制文件与文本文件的优点,以线状数据为例设计了便于文档序列化,易于面向对象ＧＩＳ进行了的二进矢量地图文件格式。     

顶面倾斜电视塔架柱基础的放样、检测及成果统计分析

本文结合具体工程,叙述了用精密水准控制顶面倾科的巨型电视塔架柱基础顶面,以及用高精度控制点控制塔架柱基础顶面中心位置的测设方案,进行了检测成果的统计分析,从而保证了测设精度的成功作法。     

A new method for GLONASS inter-frequency bias estimation based on long baselines

GPS Solutions - Frequency division multiplexing of GLONASS signals causes inter-frequency bias (IFB) in receiving equipment. IFB significantly increases the difficulties of fixing GLONASS...     

Improving BDS integer ambiguity resolution using satellite-induced code bias correction for precise orbit determination

GPS Solutions - Successful resolution of integer ambiguity over long baselines is a key to improve the accuracy of precise orbit determination for global navigation satellite system satellites. The...