钟山风景区电子地图设计与实现

随着电子地图的不断发展,其在智慧旅游中扮演的角色越来越重要.钟山风景区电子地图主要将三个风景区融为一体,既突出单个景点的特色,又从空间上直观反映景区间的联系.制作便民的钟山风景区电子地图有利于引导南京旅游业的发展.     

Accuracy Assessment of the TOPEX/Poseidon Ionosphere Measurements

We conducted an assessment of the TOPEX dual-frequency nadir ionosphere observations in the TOPEX/Poseidon (T/P) GDR by comparing TOPEX with the Center for Orbit Determination in Europe (CODE) Global Ionosphere Map (GIM), the climatological model IRI2001, and the DORIS (onboard T/P) relative ionosphere delays. We investigated the TOPEX (TOPEX Side A and TOPEX Side B altimeters, TSA and TSB, respectively) ionosphere observations for the time period 1995–2001, covering periods of low, intermediate, and high solar activity. Here, we use absolute path delays (at Ku-band frequency of the TOPEX altimeter and with positive signs) rather than Total Electron Content (TEC). We found significant biases between GIM and TOPEX (GIM–TOPEX) nadir ionosphere path delays: ?8.1 ± 0.4 {mm} formal uncertainties and equivalent to 3.7 TECu) and ?9.0 ± 0.7 {mm} (4.1 TECu) for TSA and TSB, respectively, indicating that the TOPEX path delay is longer (or with higher TECu) than GIM. The estimated relative biases vary with latitude and with daytime or nighttime passes. The estimated biases in the path delays (DORIS–TOPEX) are: ?10.9 ± 0.4 {mm} (5.0 TECu) and ?14.8 ± 0.6 {mm} (6.7 TECu), for TSA and TSB, respectively. There is a distinct jump of the DORIS path delays (?3.9 ± 0.7 {mm}, TSA delays longer than TSB delays) at the TSB altimeter switch in February 1999, presumably due to inconsistent DORIS processing. The origin of the bias between GIM (GPS, L-band) and TOPEX (radar altimeter, Ku-band) is currently unknown and warrants further investigation. Finally, the estimated drift rates between GIM and TSA, DORIS and TSA ionosphere path delays for the 6-year study span are ?0.4 mm/yr and ?0.8 mm/yr, respectively, providing a possible error bound for the TOPEX/Poseidon sea level observations during periods of low and intermediate solar activity.     

基于知识的点状符号自动识别

文中根据地形图黑版要素中点状符号的特点,总结了6种易于表达的知识特征,并据此提出了一种基于知识的点状符号识别方法。     

Measured and perceived visual complexity: a comparative study among three online map providers

We present a study on human perception of map complexity, with the objective of better understanding design decisions that may lead to undesirable levels of complexity in web maps. We compare three complexity metrics to human ratings of complexity obtained through a user survey. Specifically, we use two algorithmic approaches published by others, which measure feature congestion (FC) and subband entropy (SE), as well as our own approach of counting object types rather than individual objects. We compare these metrics with each other as well as with human complexity ratings for three maps of the same area from map providers Google Maps, Bing Maps, and OpenStreetMap. Each map design is assessed at three different scales (levels of detail). We find that (1) the FC and SE metrics appear to be adequate predictors of what humans consider complex; (2) object-type counts are slightly less successful at predicting human-rated complexity, implying that clutter is more important in perceived complexity than diversity of symbology; and (3) generalization choices do impact human complexity ratings. These findings contribute to our understanding of what makes a map complex, with implications for designing maps that are easy to use.     

Fourier-based multi-scale representation and progressive transmission of cartographic curves on the internet

ABSTRACT

Automatic generation of multi-scale representations from the same spatial data source has been the research focus in map generalization for a long time. Based on the Fourier technique, this paper proposes a continuous, multi-scale representation model for progressive transformation of cartographic curves on the Internet. In our method, all the curves, whether closed or open, are depicted as periodical functions which are further expressed as Fourier series. The convergence degrees of the Fourier series are explored for different kinds of curves, and truncating frequencies are derived based on the similarity between the original and reconstructed curves. Using information theory and the Radical Law in cartography, the relationship between map scales and Fourier frequencies is established. Based on the proposed multi-scale model, we also introduce the principles and implementation of a progressive transmission method. Our method is evaluated using the contours from a topographic map. The results show that our model is a valid approach to multi-scale representation of cartographic curves.     

“智慧地图”体系构建研究

随着“智慧地球”“智慧城市”的发展,以及人类科学技术和对自然认识水平的提高,传统的空间信息显示与简单的数据存储、管理已不能满足我们对空间认知的需求,空间信息获取的广泛性、时效性、便捷性以及地图服务的智能化与人性化已经成为当前地图行业需求热点.同时,物联网、云计算等新兴信息技术的迅速发展所引爆的第三代信息革命为现代地图学的发展带来了新的契机.本文以地图学历史发展为主线,系统梳理“地图”的相关概念、内涵及技术理论,并结合当前经济、社会及技术背景,重新整合地图的发展需求、内涵及技术体系,提出一种全新的“智慧地图”概念,为现代地图学及数字地图技术的发展提供一种新的视角与理论方法框架.     

基于全景真三维斜射影像的数字城管应用研究

随着国家智慧城市试点工作如火如荼的开展,数字城管作为智慧城市业务应用体系的重要组成部分,正成为各地探索创新应用的重要领域。洛阳市数字城管率先采用先进的全景真三维斜射影像技术,实现了快速的城市部件数据普查,创造了全新的用户体验,满足了专业化的城市管理应用需求,创新了＂全景化＂的数字城管应用新模式。     

双等距离投影及其应用

双等距离投影是指自图上两定点出发至图上任意点间的距离都与实地等长的投影。本文先从球面极坐标出发，讨论了双等距离投影公式的建立，继而给出了在地理坐标下的正轴和斜轴投影计算方法。本文证明了该投影的性质属任意投影，其计算方法是可行的，有实用价值。双等距离投影在测量上可用于圆圆系统定位，在军事上可用于敌情监测等。     

基于SuperMap IS的WebGIS开发

WebGIS是将Web技术和GIS技术相结合的新技术,有着广泛的应用。通过WebGIS技术,客户端仅需使用浏览器(不一定包含专门插件)就可以对分布在Web上的GIS数据进行查询、分析等交互操作。探讨了利用Super-Map网络GIS技术,以SuperMap DeskPro作为后台GIS服务平台,通过SuperMap IS实现用户利用浏览器获得一个地理信息系统中的数据和功能的服务,论述开发和建设WebGIS的过程。     

二元样条最小二乘在地图投影数据加密中的应用

首先讨论了二元样条最小二乘拟合的原理和计算方法,然后给出了该方法在地图投影数据加密中的应用。结论表明,所述方法具有很好的精度和稳定性。