Volker Coors

Meeting the spirit of history

This paper describes a research and development project for a novel technology, making the conveyance of cultural heritage during a historic sightseeing tour a unique experience. The cornerstones of this system are mobile augmented reality, including a hybrid tracking approach, intelligent queries to pose complex questions about geographical and historical knowledge, as well as a story engine to interactively run a digital story. This system involves the user in a thrilling story while exploring the history and the attractions of the city.

Delphi: geometry-based connectivity prediction in triangle mesh compression

AbstractDelphi is a new geometry-guided predictive scheme for compressing the connectivity of triangle meshes. Both compression and decompression algorithms traverse the mesh using the EdgeBreaker state machine. However, instead of encoding the EdgeBreaker clers symbols that capture connectivity explicitly, they estimate the location of the unknown vertex, v , of the next triangle. If the predicted location lies sufficiently close to the nearest vertex, w , on the boundary of the previously traversed portion of the mesh, then Delphi estimates that v coincides with w . When the guess is correct, a single confirmation bit is encoded. Otherwise, additional bits are used to encode the rectification of that prediction. When v coincides with a previously visited vertex that is not adjacent to the parent triangle (EdgeBreaker S case), the offset, which identifies the vertex v , must be encoded, mimicking the cut-border machine compression proposed by Gumhold and Strasser. On models where 97% of Delphi predictions are correct, the connectivity is compressed down to 0.19 bits per triangle. Compression rates decrease with the frequency of wrong predictors, but remains below 1.50 bits per triangle for all models tested.

Geometric-Semantical Consistency Validation of CityGML Models

In many domains, data quality is recognized as a key factor for successful business and quality management is a mandatory process in the production chain. Automated domain-specific tools are widely used for validation of business-critical data. Although the workflow for 3D city models is well-established from data acquisition to processing, analysis and visualization, quality management is not yet a standard during this workflow. Erroneous results and application defects are among the consequences of processing data with unclear specification. We show that this problem persists even if data are standard compliant and develop systematic rules for the validation of geometric-semantical consistency. A test implementation of the rule set and validation results of real-world city models are presented to demonstrate the potential of the approach.

Presenting Route Instructions on Mobile Devices: From Textual Directions to 3D Visualization

Publisher Summary This chapter reviews several means of presenting route instructions to a mobile user. It highlights some general considerations for presentations on mobile devices and discusses the process of generating route instructions, presenting route instructions, and technical issues associated with presenting route information in 3D. To produce a presentation that is appropriate for the current situation, it is necessary to adapt it to situational factors such as the currently available resources or the quality of the available positional information. Especially, when generating a presentation on mobile devices, two types of resources are of special importance: (1) Technical resources including factors such as speed, bandwidth and screen resolution and (2) The cognitive resources of the user that impact the way that information should be presented to the user. In addition to cognitive and technical resources, the users current position is not only a key factor in determining the kind of situation a mobile user is in but also highly relevant in the context of generating and presenting route instructions. For example, knowing the users current location is vital if the beginning of a route corresponds to his/her current location, which frequently occurs in the case of a mobile user.

Towards Automatic Validation and Healing of CityGML Models for Geometric and Semantic Consistency

A steadily growing number of application fields for large 3D city models have emerged in recent years. Like in many other domains, data quality is recognized as a key factor for successful business. Quality management is mandatory in the production chain nowadays. Automated domain-specific tools are widely used for validation of business-critical data but still common standards defining correct geometric modeling are not precise enough to define a sound base for data validation of 3D city models. Although the workflow for 3D city models is well-established from data acquisition to processing, analysis and visualization, quality management is not yet a standard during this workflow. Processing data sets with unclear specification leads to erroneous results and application defects. We show that this problem persists even if data are standard compliant. Validation results of real-world city models are presented to demonstrate the potential of the approach. A tool to repair the errors detected during the validation process is under development; first results are presented and discussed. The goal is to heal defects of the models automatically and export a corrected CityGML model.

The influence of data quality on urban heating demand modeling using 3D city models

Abstract 3D city models are rich data sets for urban energy analyses, providing geometrical and semantic data required to estimate the energy demand of entire districts, cities and even regions. However, given the diverse availability, uncertainty and Level of Details of these data and the resources required to collect them, managing data quality is a common challenge of urban energy modeling. Knowing the influences of the different input data for different configurations and applications enables to control the result accuracy and recommend intelligent and adequate data collecting strategies, by assigning resources on the most important parameters. This paper investigates the influences of geometrical, meteorological, semantic and occupancy related data quality on the heating demand estimated by the urban energy simulation platform SimStadt, applied to the City of Ludwigsburg in Germany. A focus on a district with consumption data available at building block level allows for a critical comparison between estimated and measured energy demands. Although the quantified information presented in this paper is specific to a case study, the main trends and developed methods are transferrable to other urban energy analysis studies based on 3D city models.

An Energy-Related CityGML ADE and Its Application for Heating Demand Calculation

Different associated properties of city models like building geometries, building energy systems, building end uses, and building occupant behavior are usually saved in different data formats and are obtained from different data sources. Experience has shown that the integration of these data sets for the purpose of energy simulation on city scale is often cumbersome and error prone. A new application domain extension for CityGML has been developed in order to integrate energy-related figures of buildings, thermal volumes, and facades with their geometric descriptions. These energy-related figures can be parameters or results of energy simulations. The applicability of the new application domain extension has been demonstrated for heating energy demand calculation.

An integration of urban spatial data with energy simulation to produce X3D city models: the case of Landkreis Ludwigsburg

In this paper, we describe a chain of steps to produce X3D city models based on transformation and integration of urban 3D CityGML models with DTM tiles, orthophotos and energy simulation outcome of energy demand and photovoltaic potential generated by the SimStadt platform.

Benefits through Linking of analogue and digital Maps

Despite their popularity electronic maps on mobile devices have not eliminated the use of paper maps. Conventional paper maps can offer a quick overview due to their large format while the map content on mobile devices is adjusted to the limited display size. However the electronic map applications provide many additional functions that paper cannot offer. The authors provide arguments for the linking of the two worlds through explaining how the advantages of both media complement each other. Hence, an approach to bridge the technological gap between analogue paper and the electronic domain is presented. A technology developed by Swedish company Anoto is used to enhance regular paper with an unobtrusive dot pattern enabling an electronic pen with a camera to determine its position on the paper. The potential benefits of this technology are discussed on the basis of two application scenarios that can demonstrate the feasibility of the linking of digital and analogue media and its benefits for the map user.

A framework for server side rendering using OGC's 3D portrayal service

Today various data formats and different browser based 3D globes and other viewer implementations are available. To enable interoperable visualizations between them and to integrate the distributed data, a standardized interface on the server side is necessary for the portrayal of 3D geospatial data. We therefore present a framework implementing the new 3D Portrayal Service standard (3DPS) of the Open Geospatial Consortium (OGC). The focus of the paper is on the View conformance class of the 3DPS that supports the delivery of server-side rendered high resolution images. An introduction to the main aspects and features of the 3DPS standard is given. The framework controls the workflow from the storage of geographical raw data to the creation of the visual end result. The framework is open for extensions giving the ability to utilize different technologies. On the other hand the framework encapsulates server technology and starts server instances, which scale to handle a massive amount of requests. The framework implementation also inherits the 3DPS specific implementation overhead, allowing the framework user to focus on implementing his technology. Building upon the framework, two prototypical applications are presented, which use different renderers, data formats and storage solutions. Based on these two prototype service implementations, a distributed data set is integrated in a web-based visualization. It shows that geospatial data can be served by different independent data providers without a data integration on the data model level. The results are a significant step forward to a 3D distributed geospatial data infrastructure based on open standard service interfaces. In addition, the use of different data formats produced interesting insights in their performance for server-side rendering. This work will be beneficial for researchers wanting to support 3DPS GetView without having to take care of the standards overhead and the implicitly needed server implementation.