国土资源管理信息系统的安全建设初探

随着国土资源信息系统建设的不断扩大和应用,信息系统安全问题日益突出。本文着重阐述了系统安全建设的特点、建设内容和建设原则,并对国土资源信息系统安全建设进行了探讨。     

A high-precision heuristic model to detect home and work locations from smart card data

Smart card-automated fare collection systems now routinely record large volumes of data comprising the origins and destinations of travelers. Processing and analyzing these data open new opportunities in urban modeling and travel behavior research. This study seeks to develop an accurate framework for the study of urban mobility from smart card data by developing a heuristic primary location model to identify the home and work locations. The model uses journey counts as an indicator of usage regularity, visit-frequency to identify activity locations for regular commuters, and stay-time for the classification of work and home locations and activities. London is taken as a case study, and the model results were validated against survey data from the London Travel Demand Survey and volunteer survey. Results demonstrate that the proposed model is able to detect meaningful home and work places with high precision. This study offers a new and cost-effective approach to travel behavior and demand research.     

Re-examining urban region and inferring regional function based on spatial–temporal interaction

Urban system is shaped by the interactions between different regions and regions planned by the government, then reshaped by human activities and residents’ needs. Understanding the changes of regional structure and dynamics of city function based on the residents’ movement demand are important to evaluate and adjust the planning and management of urban services and internal structures. This paper constructed a probabilistic factor model on the basis of probabilistic latent semantic analysis and tensor decomposition, for purpose of understanding the higher order interactive population mobility and its impact on urban structure changes. First, a four-dimensional tensor of time (T)?×?week (W)?×?origin (O)?×?destination (D) was constructed to identify the day-to-day activities in three time modes and weekly regularity of weekday/weekend pattern. Then we reclassified the urban regions based on the space clustering formed by the space factor matrix and core tensor. Finally, we further analysed the space–time interaction on different time scales to deduce the actual function and connection strength of each region. Our research shows that the application of individual-based spatial–temporal data in human mobility and space–time interaction study can help to analyse urban spatial structure and understand the actual regional function from a new perspective.     

像平面坐标到经纬度坐标的转换

坐标转换是所有的遥感、GIS、航测等软件都必须具备的一个基本功能,在功能实现中会遇到大规模的矩阵运算问题,而灵活运用IDL编程工具中的结构数组运算能大大地简化计算步骤,加快图像处理的速度。本文运用IDL设计了坐标转行算法,对于一幅row(行)、col(列)的图像,在已知该幅图像其中一个像元点在图像中的像元位置和经纬度坐标的情况下,利用该算法能够实现整幅图像中所有点的经纬度坐标的计算,并验证了其正确性。     

大比例尺数字测图及常见问题分析

概要介绍了数字测图的基本思想、系统、作业模式和作业过程,在此基础上结合实际生产对全野外数字测图各工序中存在的不规范作业及成果质量问题进行了归纳,并对产生问题的原因进行了分析。     

An enhanced bit-wise parallel algorithm for real-time GPS software receiver

Software-based global positioning system (GPS) receivers perform all the baseband signal processing and the high level functions on a general purpose processor. The heavy computational loads of the signal correlation in baseband processing make it difficult for software receivers to operate in real time. In order to improve the real-time performance, an enhanced bit-wise parallel algorithm has been developed in this study. The enhanced algorithm has been implemented and tested in a 12 channels real-time GPS software receiver. The system consists of a radio frequency front end, a data acquisition board and software that runs on a laptop with a Pentium-M 1.5 GHz processor running the Window^® XP operating system. The data acquisition board packs the 2-bit intermediate frequency samples with a 2-bit in/8-bit out shift register and transfers the packed samples to laptop through a USB port. The software running on the laptop performs all the baseband and navigation processing in real time. The test results show that the enhanced algorithm significantly improves the real-time performance of the software receiver by reducing the computational operations for signal correlation by 50% compared with the existing bit-wise parallel algorithm. Furthermore, the enhanced algorithm also reduces the amount of required memory for storing data for signal correlation.     

城市公众地理信息服务系统的开发应用

目前对城市公众地理信息服务的需求越来越多样化。利用ArcGISServer开发了基于三维仿真电子地图的城市公众地理信息服务平台,重点实现了城市公众地理信息服务平台的关键技术,并在某市公众地理信息服务平台的应用中取得良好的效果。     

单基站CORS-RTK转换参数与数据处理

依据某城市单基站CORS实测数据,对用不同数目与分布的已知点求解转换参数对模型的内符合精度和外符合精度的影响进行分析;并且提出了采用极大验后滤波进行测量数据后处理,以提高测量的精度。对单基站CORS-RTK的建立和应用具有较先进的指导意义。     

EXCEL在高精度广东省第二次土地调查控制面积计算中的应用

行政区控制面积计算是第二次土地调查的一项重要工作。本文介绍了广东省第二次土地调查行政区控制面积计算的方法与生产过程,及各软件配合使用的情况、EXCEL的部分实用功能和运用EXCEL软件在本项目中计算、检查的一些应用案例和经验。     

联合战役地形分析

首次提出联合战役地形分析的概念,并分析了联合战役地形分析应用的主要时机和要求。论述确定地形分析基本任务的逻辑关系,并分别研究了联合战役地形分析各基本内容的概念与分析方法。