Geography Markup Language Research Articles

Towards effective GML data management: framework and prototype

Geography Markup Language (GML) is composed of non-spatial information as properties of geographical features and spatial information as geometry. With the feature of XML-encoding and well-formed specification, GML has been widely used in various application systems as internal representation of geo-spatial data for its efficient interoperability in heterogeneous systems. This arises the demand to effectively manipulate GML data. The separate GML processing technology cannot provide a whole geo-spatial data management service for users. In this paper, we propose a GML data management framework and analyse how the relative technologies cooperate to meet the demand of geo-spatial data representing, processing and exchanging. Storage, index and query approaches, and corresponding integration technology are presented based on the proposed framework. The prototype of GML data management system (GDMS) was implemented based on the proposed framework.

Transforming GML to Presentation Languages by Extending XSLT

Diversity of practices and methods in all fields is the basis of emerging standards in different areas. World Wide Web Consortium (W3C) has standardized eXtensible Markup Language (XML) as a very convenient tool to structure data for numerous purposes. OGC standardized Geography Markup Language (GML), which is an XML-based language, to store and transport geospatial data. Despite the fact that it is a medium to separate georeferenced data from presentation, GML by itself is not intended to visualize geo-referenced data. One of the solutions to visualize GML is to use eXtensible Style sheet Language Transformation (XSLT) as transformer to a visualization language such as Scalable Vector Graphic (SVG). Unlike the usual procedure, the major advantage of the proposed approach is that the transformation process is shifted to the client-side. XSLT as a median language is a general-purpose transformation tool. As it is not specialized for map cartography, map making process is very complicated using this primitive language. To facilitate transformation process, in this research, XSLT is extended to meet cartography requirements. Furthermore, a graphical user interface (XCartoT) is designed to set all the map properties interactively. XCartoT provides a user-friendly interface for cartographers to automatically generate necessary XSL files for their intended maps. The goal of this research is to develop a major step towards the geospatial Web.

Design of a standardized geo-database for risk monitoring of potentially polluting marine sites

An increasing availability of geospatial marine data provides an opportunity for hydrographic agencies to contribute to the identification of potentially polluting marine sites (PPMS). This new acronym has been created not only to refer to shipwrecks of modern vessels, but also for other types of marine sites such as dumping areas, pipelines, etc. Independent of the specific type, a PPMS represents a potential source of pollution for the marine environment. Although several type-specific databases are available worldwide (from local to global scale), there is an evident lack of uniformity (e.g., different aims of data collection). A common approach description of these sites at local single-site level may permit aggregation for multi-scale decisions, e.g., for remediation and incident response. To adequately manage these sites, a standardized PPMS geospatial database (GeoDB) application has been designed to collect relevant information suitable for site inventory and geo-spatial analysis. In particular, benefits in structuring the data in conformance with the Universal Hydrographic Data Model (IHO S-100) and encoding using the Geographic Markup Language (GML) are presented. A possible practical storage solution is proposed using a GML-enabled spatial relational database management system. Finally, a Web GIS deployment is illustrated, being the simplest way to communicate to the public the collected information, with the related possibility of using the data as a Web Map Service in almost any GIS, allowing for better development and integration with other available datasets. The adoption of the PPMS GeoDB product specification as part of the IHO S-100 series would represent an innovative and important contribution from the hydrographic community to reduce, or at least better manage, environmental and economic risks related to PPMSs.

Generalization of buildings within the framework of CityGML

For a better visual impression, 3D information systems and architecture need detailed, photo-realistic visualization of 3D data-sets. However, easy accessibility with efficient rendering becomes difficult due to the detailed data associated with 3D objects. Therefore, different applications demand different levels of detail (LoD). Currently, City Geography Markup Language (CityGML), as the Open Geospatial Consortium standard, is being used to model and represent buildings in different LoDs (LoD0–LoD4), but it does not provide methods to generate different LoDs automatically. Thus, generalized (abstracted) 3D scenes of buildings need to be generated to fulfill the demands of task-specific applications by reducing data volume. This paper discusses various ways to generalize building models, within the framework of CityGML, reducing the level of detail from higher LoD to lower. The LoD4 data is parsed and analyzed. Various heuristics are applied to simplify the ground plan and the results are then aggregated. The minimum length of an edge for simplification is restricted to the CityGML generalization specifications provided and is characterized by differing accuracies and minimal dimensions of objects for LoD1 and LoD2. This could maintain the accuracy of generalized objects and avoid the elimination or merging of important features. Second, the heights of the walls of the simplified ground plans are raised with the aim to construct simplified 3D building models. Algorithms for simplification and aggregation aiming to derive LoD2 and LoD1 are implemented and tested on a number of buildings of Putrajaya, Malaysia. The experiment results show that the minimum length of edges to be simplified is inversely proportional to the size of generalized models.

Implementation of UML Schema in Relational Databases

Numerous disciplines require information concerning phenomena implicitly or explicitly associated with a location relative to the Earth. Disciplines using Geographic Information (GI) in particular are those within the earth and physical sciences, and increasingly those within social science and medical fields. Therefore geographic datasets are increasingly being shared, exchanged and frequently re-purposed for uses beyond their original intended use. Being part of the ISO 19100 Geographic Information Standard series, the ISO 19136 called Geography Markup Language (GML), defines the rules a data model described using the Unified Modeling Language (UML) has to follow in order to generate from it an XSD schema. However, if GML is essential for exchange data among different organization, it may not be the best option for persisting or searching operations. On the other side, the Relational Database Model (RDBM) has been heavily optimized over the decades to store and search data. This paper does not address “How to store an GML complaint document in an RDBM” but “How to realize an RDBM from an ISO 19100 complaint UML data model” and within this context, it describes the experience and the lessons learnt. The conclusions show how the information contained in such UML is able to produce not only representations as GML schema, but also RDBM or RDF without passing by any intermediary step.

Integrated Validation System for the Simulation of Diverse Sensors in WSNs

In wireless sensor networks (WSNs), sensors use different types of information, such as temperatures, humidity, magnetic fields, and sound; their communication distances and battery sizes and capacities may be different. Differences in communication distances and battery capacities when the same communication method is used affect the life of the entire sensor network topology. Tests for the maximum life of the sensor network topology require many sensor nodes and huge proportional costs. In addition, experiments to verify new ideas for WSNs as alternatives to existing methods also require large expenditures. Since experiments with the arrangement of actual sensors are expensive, such experiments are conducted using simulators so that solutions for protocol design and verification can be compared through software. Existing simulators are tailored to certain sensor characteristics, so that only quite limited results can be obtained through the implementation of simulated operations, simulations of sensor arrangements, and the comparison of limited information transmission routing functions provided by simulators. This paper proposes diverse sensor definable simulators (DSDs) for the performance of experiments on diverse sensors with different communication distances in WSN environments where Geography Markup Language (GML) based coordinates are utilized.

A UNIFIED APPROACH FOR 3D GENERALIZATION OF BUILDING MODELS IN CITYGML

Abstract. Task-specific applications demand abstractions (generalized) 3D scenes of 3D models to be used for visualization and analysis purposes. Therefore, lower LoDs (level-of-details) from higher LoDs need to be made available to these applications. A unified generalization framework is proposed to derive multiple LoDs (LoD3-LoD1) taking both semantics and geometric aspects of 3D buildings modelled in CityGML (City Geography Markup Language) into account. For this purpose, interior structures of 3D objects at LoD4 are removed to derive LoD3 and openings (door, windows) are removed from LoD3 to derive LoD2. Remaining parts such as outer installations and walls are projected onto the ground and simplified based on CityGML generalization specifications. Algorithms for simplification with the aim to derive LoD1 from LoD2 are implemented and tested on a number of buildings of Putrajaya city, Malaysia.The experiments shows that elimination of important part (s) or merging could be avoided by applying semantic-based removal of objects at different LoDs.

A three-step strategy for generalization of 3D building models based on CityGML specifications

3D building models of the world exhibit multi-scale properties. Different level-of-details (LoDs) are important for different applications. Therefore, generation of multi-scale representation of 3D building models to fulfill the demands of these applications is a generalization problem. In order to generalize 3D buildings, different pieces of information need to be preserved or removed to restrict the amount of data represented on a certain LoD. In this work, a three-step strategy based on simplification, aggregation and reconstruction of generalized buildings represented in City Geography Markup Language (CityGML) is proposed. The minimum length of edges (threshold value) for removal of amount of data is restricted to generalization specifications of CityGML characterized by differing accuracies and minimal dimensions of objects for each LoD. The main part of this paper is simplification of ground plans. For this purpose, a new approach is proposed to restrict number of edges, curves, and corners of ground plan of 3D building model on a certain LoD. Algorithms for simplification with the aim to derive LoD1 from exterior shells of buildings at LoD3 are implemented and tested on a number of buildings of Putrajaya city. The experiments showed that length of edge as threshold value is directly proportional to the size of generalized models.

Pioneering GML Deployment for NSDI — Case Study of USTIGER/GML

The National Spatial Data Infrastructure (NSDI) is defined as the technologies, policies and people necessary to promote sharing of geospatial data throughout all levels of government, the private and non-profit sectors and the academic community. The US Census Bureau is the federal agency lead for administrative units data, one of the seven data themes identified by the NSDI framework. The administrative unit is a unit with administrative responsibilities. These units are organized as nodes/lines/areas feature data. The OpenGIS Geography Markup Language (GML) is the XML grammar to express the geographic features. This study at the US Census Bureau investigates how the general-purpose GML standard could be leveraged and extended to describe the most comprehensive geographic dataset with national coverage in the US. Challenges and problems in dealing with data volume, GML document structure, GML schema design and GML document naming are analyzed, followed by proposed solutions proven for feasibility. Our results show that one key point in making a successful GML deployment for NSDI is to reflect the characteristics of the geographic data through a carefully designed GML schema, structure and organization. The lessons learned may be useful to others transforming NSDI framework data and other large geospatial datasets into GML structures.

A GML-based approach to automate spatial metadata updating

With the huge amount of spatial data created and updated in short time frames and exchanged frequently over the Web, the demand for updating dataset and metadata in real time to provide users with the most up-to-date, precise, reliable, and complete metadata is increasing dramatically. So far, different metadata-updating approaches have been introduced to the spatial industry of which their issues and challenges have prohibited them from being adopted widely. Using the detached metadata data model and being limited to some dataset formats are some of these issues. To respond to this challenge, this article presents a new synchronization approach to automatically update the ISO 19115 core metadata elements which are affected by the (vector-based) dataset modification. Based on this approach, this article describes the major technical requirements considered necessary for the implementation phase, such as an integrated data model to couple dataset and metadata rooted in Geography Markup Language (GML) Application Schema, a mapping software application to support required Web Services, a user-friendly interface providing a visual modification facility, and an automatic metadata-updating process which is dataset format neutral. In order to prove the synchronization concept, the automatic synchronization approach has been prototyped and integrated with the GeoNetwork opensource environment. This article discusses the architecture designed for implementing the prototype system which contains three layers: storage, service (consisting of a synchronization service entitled ‘SYNC’), and application. The standards and open source technologies selected to develop the prototype system such as deegree, GeoNetwork, PostGIS, GML, Web Feature Service-Transaction, and CSW are then explained in more detail. Finally, the issues and challenges encountered during the implementation phase and the future direction are discussed in this article.

Geography Markup Language: GML Based Representation of Time Serie of Assimilation Data and Its Application to Animation Content Creation and Representations

Method for Geography Markup Language: GML based representation of time series of assimilation data and its application to animation content creation and representations is proposed. It is validated the proposed method with NCEP/GDAS assimilation data. Also usefulness of the proposed interpolation method with tweening method is confirmed for unequal time interval of the time series data.

The GPlates Geological Information Model and Markup Language

Abstract. Understanding tectonic and geodynamic processes leading to the present-day configuration of the Earth involves studying data and models across a variety of disciplines, from geochemistry, geochronology and geophysics, to plate kinematics and mantle dynamics. All these data represent a 3-D spatial and 1-D temporal framework, a formalism which is not exploited by traditional spatial analysis tools. This is arguably a fundamental limit in both the rigour and sophistication in which datasets can be combined for geological deep time analysis, and often confines the extent of data analyses to the present-day configurations of geological objects. The GPlates Geological Information Model (GPGIM) represents a formal specification of geological and geophysical data in a time-varying plate tectonics context, used by the GPlates virtual-globe software. It provides a framework in which relevant types of geological data are attached to a common plate tectonic reference frame, allowing the data to be reconstructed in a time-dependent spatio-temporal plate reference frame. The GPlates Markup Language (GPML), being an extension of the open standard Geography Markup Language (GML), is both the modelling language for the GPGIM and an XML-based data format for the interoperable storage and exchange of data modelled by it. The GPlates software implements the GPGIM allowing researchers to query, visualise, reconstruct and analyse a rich set of geological data including numerical raster data. The GPGIM has recently been extended to support time-dependent geo-referenced numerical raster data by wrapping GML primitives into the time-dependent framework of the GPGIM. Coupled with GPlates' ability to reconstruct numerical raster data and import/export from/to a variety of raster file formats, as well as its handling of time-dependent plate boundary topologies, interoperability with geodynamic softwares is established, leading to a new generation of deep-time spatio-temporal data analysis and modelling, including a variety of new functionalities, such as 4-D data-mining.

EXTRACTING SEMANTIC BUILDING MODELS FROM AERIAL STEREO IMAGES AND CONVERSION TO CITYGML

Abstract. The collection of geographic data is of primary importance for the creation and maintenance of a GIS. Traditionally the acquisition of 3D information has been the task of photogrammetry using aerial stereo images. Digital photogrammetric systems employ sophisticated software to extract digital terrain models or to plot 3D objects. The demand for 3D city models leads to new applications and new standards. City Geography Mark-up Language (CityGML), a concept for modelling and exchange of 3D city and landscape models, defines the classes and relations for the most relevant topographic objects in cities and regional models with respect to their geometrical, topological, semantically and topological properties. It now is increasingly accepted, since it fulfils the prerequisites required e.g. for risk analysis, urban planning, and simulations. There is a need to include existing 3D information derived from photogrammetric processes in CityGML databases. In order to filling the gap, this paper reports on a framework transferring data plotted by Erdas LPS and Stereo Analyst for ArcGIS software to CityGML using Safe Software's Feature Manupulate Engine (FME)

AutoConViz: automating the conversion and visualization of spatio-temporal query results in GIS

In recent years, large multifaceted spatial, temporal, and spatio-temporal databases have attained significant popularity and importance in the database community. In order to perform preliminary investigation, exploratory visual analysis of such data-sets is highly desirable. To facilitate the convenient and efficient visualization, scientists and practitioners often need to convert the spatial component of the data-set into a more usable format. Though among the various formats available today in spatial data science community, Geographical Markup Language (GML) adheres to its central position and is of our interest in this work. The development of a tool to satisfy the spatial format conversion needs tailored to every user’s needs from scratch is difficult, time-consuming, and requires skills not easy to possess. We developed AutoConViz, to solve the issue stated above. It accepts the spatial component in GML format, converts that into shapefile format, and facilitates informative and automated interaction with the data-sets. It supports basic query and geospatial analysis and visualization tasks and offers functionalities such as zooming, panning, and feature selection. Furthermore, our software leverages navigation to classical ArcGIS software interface for users interested in more intensive analysis. AutoConViz serves both the database and geographical information system communities to explore insights of spatio-temporal databases and will help to further geospatial research and development.

A three-step approach of simplifying 3D buildings modeled by CityGML

CityGML (City Geography Markup Language), the OGC (Open Open Geospatial Consortium) standard on three-dimensional (3D) city modeling, is widely used in an increasing number of applications, because it models a city with rich geometrical and semantic information. The underlying building model differentiates four consecutive levels of detail (LoDs). Nowadays, most city buildings are reconstructed in LoD3, while few landmarks in LoD4. For visualization or other purposes, buildings in LoD2 or LoD1 need to be derived from LoD3 models. But CityGML does not indicate methods for the automatic derivation of the different LoDs. This article presents an approach for deriving LoD2 buildings from LoD3 models which are essentially the exterior shells of buildings without opening objects. This approach treats different semantic components of a building separately with the aim to preserve the characteristics of ground plan, roof, and wall structures as far as possible. The process is composed of three steps: simplifying wall elements, generalizing roof structures, and then reconstructing the 3D building by intersecting the wall and roof polygons. The first step simplifies ground plan with wall elements projected onto the ground. A new algorithm is developed to handle not only simple structures like parallel and rectangle shapes but also complicated structures such as non-parallel, non-rectangular shapes and long narrow angles. The algorithm for generalizing roof structure is based on the same principles; however, the calculation has to be conducted in 3D space. Moreover, the simplified polygons of roof structure are further merged and typified depending on the spatial relations between two neighboring polygons. In the third step, generalized 3D buildings are reconstructed by increasing walls in height and intersecting with roof structures. The approach has been implemented and tested on a number of 3D buildings. The experiments have verified that the 3D building can be efficiently generalized, while the characteristics of wall and roof structure can be well preserved after the simplification.

CityGML – Interoperable semantic 3D city models

CityGML is the international standard of the Open Geospatial Consortium (OGC) for the representation and exchange of 3D city models. It defines the three-dimensional geometry, topology, semantics and appearance of the most relevant topographic objects in urban or regional contexts. These definitions are provided in different, well-defined Levels-of-Detail (multiresolution model). The focus of CityGML is on the semantical aspects of 3D city models, its structures, taxonomies and aggregations, allowing users to employ virtual 3D city models for advanced analysis and visualization tasks in a variety of application domains such as urban planning, indoor/outdoor pedestrian navigation, environmental simulations, cultural heritage, or facility management. This is in contrast to purely geometrical/graphical models such as KML, VRML, or X3D, which do not provide sufficient semantics. CityGML is based on the Geography Markup Language (GML), which provides a standardized geometry model. Due to this model and its well-defined semantics and structures, CityGML facilitates interoperable data exchange in the context of geo web services and spatial data infrastructures. Since its standardization in 2008, CityGML has become used on a worldwide scale: tools from notable companies in the geospatial field provide CityGML interfaces. Many applications and projects use this standard. CityGML is also having a strong impact on science: numerous approaches use CityGML, particularly its semantics, for disaster management, emergency responses, or energy-related applications as well as for visualizations, or they contribute to CityGML, improving its consistency and validity, or use CityGML, particularly its different Levels-of-Detail, as a source or target for generalizations.This paper gives an overview of CityGML, its underlying concepts, its Levels-of-Detail, how to extend it, its applications, its likely future development, and the role it plays in scientific research. Furthermore, its relationship to other standards from the fields of computer graphics and computer-aided architectural design and to the prospective INSPIRE model are discussed, as well as the impact CityGML has and is having on the software industry, on applications of 3D city models, and on science generally.

Data Sharing of Digital Basin Based on GML

The data for establishing digital basin has the features of large quantity, heterogeneity and multiple dimensions. Determining how to effectively manage and share the data is the key for digital basin. This paper shows an information sharing model for digital basin based on metadata directory, Service-Oriented Architecture (SOA) and publishing/subscription technology. And then, for easily transmission, we preliminarily accomplish the data conversion based on Geography Markup Language (GML).

3D Building Modeling and Indoor Fire Event Representation in CityGML

3-dimensional (3D) city model is increasingly popular in urban planning and disaster management. City Geographic Markup Language (CityGML) is an open data model and XML-based format for the representation and exchange of virtual 3D city model. This paper analyzed the modeling mechanism of 3D CityGML building model in LOD4 (Level of Detail) and proposed a method representing a fire event in CityGML. Our method included three operations：1) editing of building’s hierarchy and attributes information; 2) representing of semantic information of buildings surfaces, roof height and interior furniture; 3) representing of fire event by a vivid icon. With our method, 3D building model and indoor fire event can be both represented in CityGML, which is important to analyses urban emergency events.

MSNS: mobile sensor network simulator for area coverage and obstacle avoidance based on GML

Abstract A mobile sensor network is a distributed collection of sensors, each of which has sensing, computation, communication, and locomotion capabilities. In particular, locomotion facilitates the ability to self-deployment. In such a network of self-deployable mobile sensors, it is difficult to evaluate the effectiveness of mobile sensor network deployment in a given target area because we cannot predict the coverage rate for the target area. The coverage rate will be changed due to the number of sensor required in the target area, connectivity degree to be maintained and unknown obstacles. In this article, we develop mobile sensor network simulator (MSNS) in order to visualize (1) coverage secured by mobile sensors and (2) avoidance of obstacle objects (building, road and wall, and so on) on the real map drawn by GML (Geography Markup Language). From a user, MSNS receives the number of mobile sensor nodes, connectivity degree, sensor node's sensing range, communication range, and supersonic wave range. And then it visualizes the location information of sensor nodes, connectivity degree, and sensing coverage, all of which change with simulation time. Thereby we can estimate how many nodes are required in a given target area, and also calculate coverage rate of the target area in advance to the real deployment of mobile sensors.

BPELPower—A BPEL execution engine for geospatial web services

The Business Process Execution Language (BPEL) has become a popular choice for orchestrating and executing workflows in the Web environment. As one special kind of scientific workflow, geospatial Web processing workflows are data-intensive, deal with complex structures in data and geographic features, and execute automatically with limited human intervention. To enable the proper execution and coordination of geospatial workflows, a specially enhanced BPEL execution engine is required. BPELPower was designed, developed, and implemented as a generic BPEL execution engine with enhancements for executing geospatial workflows. The enhancements are especially in its capabilities in handling Geography Markup Language (GML) and standard geospatial Web services, such as the Web Processing Service (WPS) and the Web Feature Service (WFS). BPELPower has been used in several demonstrations over the decade. Two scenarios were discussed in detail to demonstrate the capabilities of BPELPower. That study showed a standard-compliant, Web-based approach for properly supporting geospatial processing, with the only enhancement at the implementation level. Pattern-based evaluation and performance improvement of the engine are discussed: BPELPower directly supports 22 workflow control patterns and 17 workflow data patterns. In the future, the engine will be enhanced with high performance parallel processing and broad Web paradigms.