Virtual differential GPS based on SBAS signal

In order to access the satellite-based augmentation system (SBAS) service, the end user needs access to the corresponding geostationary earth orbit (GEO) satellites that broadcast the augmentation information for the region. This is normally not a problem for aviation and maritime applications, because an open sky is typically available for such applications. However, it is difficult to access the GEO satellites directly at high latitudes for land applications because of the low elevation angles to the GEO satellites (e.g., 4–22° in Finland to the European geostationary navigation overlay services [EGNOS] GEO satellites). Results from a driving test of 6,100 km in Finland show that the EGNOS GEO satellites can be accessed in only 51.8% of the driving routes. Furthermore, it is also difficult to access the GEO satellites from city canyons, because the high buildings block the GEO signals. This article presents a solution to solve this problem by creating virtual differential GPS (DGPS) reference stations using the SBAS signal in space (SIS). The basic concept is to convert the SBAS signal to Radio Technical Commission for Maritime Services (RTCM) signals, and broadcast the converted RTCM signals over the wireless Internet using the Internet radio technology. Therefore, access to the SBAS service will not be limited by low elevation angles to the GEO satellites because the converted RTCM data streams are disseminated over the wireless Internet. Furthermore, the SBAS service can then be accessed via a legacy DGPS receiver. Two test cases have been carried out with the prototype system developed by the Finnish Geodetic Institute. The test results showed that the positioning accuracy of the virtual DGPS solution was about 1–2 m at 95%, which was similar to that of the standard WAAS/EGNOS solution. The positioning accuracy was not degraded, compared to that of the standard wide area augmentation system–European geostationary navigation overlay services (WAAS/EGNOS) solution, as long as the distance between the rover receiver and the virtual DGPS reference station was less than 150 km. A preliminary driving test of 400 km carried out in southern Finland showed that the availability of the virtual DGPS solutions was 98.6% along the driving route.     

GDCORS多星系统定位平台测试与分析

广东省连续运行卫星定位服务系统(G DCORS)建成了兼容多星系统的北斗地基增强平台,组织开展了新平台与原平台的外业测试.并从内符合精度评定、重复性精度评定、外符合精度、初始化时长等方面对网络实时动态(RTK)定位结果进行了统计和比对分析.测试结果表明,新平台能够提供高可靠性、高精度的网络RTK服务.文中研究结果可为GDCORS用户使用新/原平台提供实际应用参考.     

Editorial

This article presents research that implements a fully automated workflow to generalize a 1:50k map from 1:10k data. This is the first time that a complete topographic map has been generalized without any human interaction. More noteworthy is that the resulting map is good enough to replace the existing map. Specifications for the automated process were established as part of this research.

Replication of the existing map was not the aim, because feasibility of automated generalization is better when compliance with traditional generalizations rules is loosened and alternate approaches are acceptable. Indeed, users valued the currency and relevancy of geographical information more than complying with all existing cartographic guidelines. The development of the workflow thus started with the creation of a test map with automated generalization operations. The reason for the test map was to show what is technologically possible and to refine the results based on iterative users’ evaluation. The generalization operations (200 in total) containing the relevant algorithms and parameter values were developed and implemented in one model. Particular effort was made to enrich the source data in order to improve the results. The model is context aware which means it is able to apply different algorithms or adjust parameter values in accordance with a specific area. The result of the research is a fully automated generalization workflow that produces a countrywide map at scale 1:50k from 1:10k data in 50 hours.

A fully automated workflow may be the only way to produce flexible and on-demand products; consequently, the results were implemented as a new production line in 2013. Issues for further research have been identified.     

Access to the EGNOS signal in space over mobile-IP

The EGNOS service will provide better positioning availability and accuracy than that from the standalone GPS solutions. However, in order to access the EGNOS service, the end user needs to access the corresponding GEO satellites that broadcast the augmentation information for the region. This is not a problem normally for aviation and maritime applications because an open sky is always available for such applications. However, an open sky is not always available for land applications because of the obstacles in the vicinity of the end users, for example, in the city canyons. The situation gets worse for the regions at high latitudes because the elevation angles to the GEO satellites are rather low (e.g. 4–22° in Finland). This article describes briefly the SISNeT technology, designed and developed by the European Space Agency, which allows accessing the EGNOS SIS via the Internet. It will describe in detail the handheld SISNeT receiver, designed and developed by the Finnish Geodetic Institute under ESA contract. The SISNeT data server is an IP-based server that acquires the EGNOS messages from an EGNOS receiver, and broadcasts them over the Internet in real-time. The handheld receiver consists of a GPS PC-card receiver, a GPRS (or GSM) card phone, and a pocket PC as the host platform. The receiver software is a Windows CE-based package with a multi-process and multi-thread architecture. It simultaneously receives: (1) the EGNOS SIS over a GPRS wireless connection and the Internet and (2) the NMEA messages from a serial connection to a GPS receiver. It decompresses and decodes the EGNOS messages, and utilizes the information in the messages to estimate the EGNOS-corrected coordinates, which are finally delivered to the end user via a virtual COM port. The virtual COM port has been implemented as a stream interface driver in the Pocket PC. It can be accessed in the same way as the physical COM port in a GPS receiver is accessed. Therefore, it is easy to interface to any third-party applications. The test results show that the handheld SISNeT receiver can provide a positioning accuracy of about 1–2 m for the horizontal components, and 2–3 m for the vertical component in real time. Due to the poor performance of the wireless connection, 10–30% of the EGNOS messages can be lost depending on the services provided by the wireless network operators. The impact of the messages lost on the positioning accuracy is about 0.5 m in both the horizontal and vertical components. Electronic Publication     

互联网+地表覆盖验证及应用

为有效地组织大范围地表覆盖数据验证,需要发动和组织来自不同地域、不同机构的专家,但往往缺少网络化环境下的协同验证方法和工具。针对这一问题,将互联网+、服务计算技术等与地表覆盖验证业务相融合,提出了互联网+地表覆盖验证服务模型,构建了面向互联网+的地表覆盖验证业务流程和方法,研制了基于景观形状指数（landscape shape index,LSI）抽样算法的在线验证系统GLCVal（global land cover validation）,为大范围、高分辨率地表覆盖数据验证提供了新思路、新方法。利用所提出的方法与系统,与GEO（Group of Earth Observation）、UN-GGIM（the United Nations Initiative on Global Geospatial Information Management）等组织合作开展了GlobeLand30的全球验证,有效支持了跨区域专家的主动参与、多角色协同,促进了验证资源联通和共享,提高了验证效率。     

用SVG技术构建基于GML的WebGIS

WebGIS是Internet技术与GIS相结合的产物,WebGIS为公众获取GIS数据和地理信息服务提供了一个有效的工具。但是目前许多WebGIS应用都依赖于GIS软件,由于GIS软件和数据格式多种多样,从而难以互操作,缺乏灵活性。本文以实现GIS在互联网上的传播为研究目的,探讨将SVG与GML结合应用于WebGIS的解决方案和应用模式,并详细分析了系统实现的体系结构和相关技术,着重论述了GML与SVG之间的转换方法。     

互联网时代GIS设计的新观念──以数据为中心的GIS

本文讨论了以数据为中心的GIS设计新概念。指出互联网造就了巨大的信息资源,GIS的数据源从自供自给到从网上获取是一种观念的巨大转变。进而探讨了WebGIS在网上数据服务,网上数据互操作,网上数据采掘和网上数据管理等方面的新进展和面临的新挑战。     

基于交通基础地理信息的网络发布研究与实现

近年来随着WebGIS技术的日趋成熟,采用WebGIS技术管理空间数据并进行网络发布,供用户快速查询与使用,实现空间信息的网络共享,为空间数据的充分利用和可视化表达提供了一种有效的解决方案。本文以北京市交通地理信息系统开发为例,探讨了交通基础地理信息的网络发布平台构架设计与实现过程,并针对系统关键技术的原理及实现进行了详细阐述,构建了以J2EE为核心,基于ArcIMS的空间信息服务框架体系,是WebGIS技术在交通领域的集成应用。     

基于互联网的CORS数据管理与质量检查系统开发

为了有效管理和分发连续运行参考站系统(CORS)的源数据,我们开发了基于互联网的CORS数据管理与分发系统(CorsDBMS1.0)。系统能安全、有效地管理CORS跟踪站的数据,并能根据客户需求,通过互联网实时提供单站下载、批量下载和定制下载三种形式的数据下载服务。该系统在苏州工业园区格网信息有限公司正式运行,用于管理和分发苏州CORS系统12个连续跟踪站的数据,网址为www.geone.net。     

Web GIS组件方法研究

在分析WebGIS二次开发需求的基础上，提出了基于JavaBean的WebGIS组件概念，并详细阐述其特征、体系结构和空间数据组织，结合实例Internet GIS-GeoSurfV4.0介绍了系统的设计与实现以及二次开发的方法与比较。     

地理信息服务网络与协同研究进展EI北大核心CSCD

互联网与大数据技术的高速发展为地理信息服务的互联共享与广泛应用提供了技术基础。面对资源海量、多源异构的地理信息服务,如何实现服务的有效组织并提供合理高效的服务组合,拓展地理信息服务的应用范围,满足更高层次的应用需求受到研究者的广泛关注。构建地理信息服务网络并通过语义实现服务协同,是一种可能的解决方案。本文分析了当前地理信息服务和地理信息服务网络研究的现状,依据服务网络领域的研究成果,从服务网络的表达和优化、服务协同的构建和优化两个方面探讨了基于网络构建的地理信息服务协同方法的发展潜力,进而提出了地理信息服务网络及协同面临的挑战与研究方向。     

一种基于地理空间大数据的网络舆情监测软件架构

在梳理网络舆情大数据相关理论的基础上,对网络舆情监测软件的发展现状作了全面分析,结合舆情监测系统对地理空间信息的需求和现有的不足,提出了一种基于地理空间大数据环境的网络舆情监测系统的软件架构,实现地理空间数据环境下网络舆情的数据采集及处理、地理空间专题网络舆情的可视化、地理空间深层次的数据挖掘、网络舆情的时空关联性分析等功能。研究已得到一定的实践检验,结合地理空间数据可提高网络舆情监测和管理的高效性,能有效监测网络热点事件,做到科学辅助决策。     

Generalization Services on the Web—Classification and an Initial Prototype Implementation

Much progress has been made in the field of web-based cartography through standards developed by the Open Geospatial Consortium (OGC). While automated access and presentation of cartographic data have been defined, the services for automated generalization are yet to be standardized. This paper aims to show advantages of applying the service concept to generalization and suggests several classification schemas of generalization services at different levels of granularity. A detailed explanation of a real implemented Generalization Service is provided. We show how software developers can make their generalization functionality available as a service and how these services can be accessed dynamically. For the implementation, the open source Java Unified Mapping Platform (JUMP) was extended to work as a framework for generalization. Generalization services could be used in different application scenarios, for instance as a middleware component extending a web map service with adaptive zooming or as stand-alone services supporting the production of topographic maps by national mapping agencies. They may also allow the development of a common research platform, where researchers would have access to a common generalization framework.     

Design and implementation of spatial data watermarking service system

Nowadays, more and more digitalized spatial data are sold and transmitted on the Internet. Thus, there arises an important issue about copyright protection of the digital data. To solve this problem, this paper has designed and implemented a spatial data watermarking service (SDWS) system which can provide a secure framework for data transaction and transfer via the Internet and protect the rights of both copyright owners and consumers at the same time.     

Design and implementation of spatial data watermarking service system

Nowadays, more and more digitalized spatial data are sold and transmitted on the Internet. Thus, there arises an important issue about copyright protection of the digital data. To solve this problem, this paper has designed and implemented a spatial data watermarking service (SDWS) system which can provide a secure framework for data transaction and transfer via the Internet and protect the rights of both copyright owners and consumers at the same time.     

The framework of a geospatial semantic web-based spatial decision support system for Digital Earth

Abstract

While significant progress has been made to implement the Digital Earth vision, current implementation only makes it easy to integrate and share spatial data from distributed sources and has limited capabilities to integrate data and models for simulating social and physical processes. To achieve effectiveness of decision-making using Digital Earth for understanding the Earth and its systems, new infrastructures that provide capabilities of computational simulation are needed. This paper proposed a framework of geospatial semantic web-based interoperable spatial decision support systems (SDSSs) to expand capabilities of the currently implemented infrastructure of Digital Earth. Main technologies applied in the framework such as heterogeneous ontology integration, ontology-based catalog service, and web service composition were introduced. We proposed a partition-refinement algorithm for ontology matching and integration, and an algorithm for web service discovery and composition. The proposed interoperable SDSS enables decision-makers to reuse and integrate geospatial data and geoprocessing resources from heterogeneous sources across the Internet. Based on the proposed framework, a prototype to assist in protective boundary delimitation for Lunan Stone Forest conservation was implemented to demonstrate how ontology-based web services and the services-oriented architecture can contribute to the development of interoperable SDSSs in support of Digital Earth for decision-making.     

Adaptive geo-information processing service evolution: Reuse and local modification method

Geo-information (GI) service automated composition according to user demands is a crucial task in spatial data infrastructures. State-of-the-art GI service composition approaches face serious limitations in terms of effectiveness and stability as the general GI processing service chain (GIPSC) must be generated from individual user specifications from scratch. This paper presents a novel approach called an adaptive geo-information service evolution (AgiSE) method which overcomes these limitations by adaptively reusing and modifying previously generated GIPSC. In this method, an influence domain minimisation (IDM) criterion is employed to modify the existing GIPSC to fit the new (changed) user demands through minimum revisions. The correction of local modification is ensured by process and integrity constraints. An innovative algorithm called influence domain pursuit is developed to find the optimised solution through a heuristic backward search based on the defined IDM. Experimental analysis shows the significant improvements of using AgiSE in GI services compared with existing traditional methods. The benefits of AgiSE are the improved efficiency of GI service composition and the improved executing stability of GIPSC which were achieved by reducing the service provider load. The AgiSE presented in this paper is crucial in reusing a general unified framework for GI service composition.     

An automated and optimized approach for online spatial biodiversity model: a case study of OGC web processing service

An online spatial biodiversity model (SBM) for optimized and automated spatial modelling and analysis of geospatial data is proposed, which is based on web processing service (WPS) and web service orchestration (WSO) in parallel computing environment. The developed model integrates distributed geospatial data in geoscientific processing workflow to compute the algorithms of spatial landscape indices over the web using free and open source software. A case study for Uttarakhand state of India demonstrates the model outputs such as spatial biodiversity disturbance index (SBDI) and spatial biological richness index (SBRI). In order to optimize and automate, an interactive web interface is developed using participatory GIS approaches for implementing fuzzy AHP. In addition, sensitivity analysis and geosimulation experiments are also performed under distributed GIS environment. Results suggest that parallel algorithms in SBM execute faster than sequential algorithms and validation of SBRI with biological diversity shows significant correlation by indicating high R² values.     

DGPS and RTK Positioning Using the Internet

The Internet as a basis for Real-Time Kinematic (RTK) and differential Global Positioning System (DGPS) service provides many advantages for worldwide GPS users. Among these advantages are service unification, open architecture, bidirectional communication, and scalability. The current development of this service allows users to use RTK and DGPS through the Internet with conventional accuracy over the short and medium baselines. The perspective for this service lies in the field of wide-area augmentation systems (WASS). At this stage of the Internet-based RTK and DGPS service project, the general concept, system components, draft standards, and software are developed. ? 2000 John Wiley & Sons, Inc.     

基于Java/Java 3D的地层3维建模与可视化

利用Java 3D技术建立一个地层可视化3维建模系统,实现地层3维模型漫游、旋转、剖切等功能,并以某地区地下水资源调查评价中采集的地质钻孔数据为例,验证该系统的有效性。该系统将不仅为地下水模型的3维实体建模提供理论支持,而且将推动WebGIS在地下水模型中的应用。