This article addresses the augmentation of existing building models by a-priori not observable structures such as electric installations. The aim is to unambiguously determine an electric network in an incremental manner with a minimum number of local measurements, e.g. using wire detectors, by suggesting the next measurement. Different reasoning strategies, e.g. utilizing graph-theoretical algorithms, have been presented and tested based on a hypothesis which is generated using Mixed Integer Linear Programming (MILP) while incorporating standards regarding the installation of electric wiring and findings from previous measurements. The presented method has been successfully applied on simulated and real-world buildings, it saves up to 80% of the necessary measurements compared to an exhaustive verification of the whole existing electric network, and paves the way for efficiently extending existing models, e.g. GIS models, with information on hidden utilities. This opens up new opportunities to model further infrastructures, e.g. water pipes, in future research.

doi:10.1016/j.autcon.2022.104571

@article{dehbi2022incrementalConstraint-based,
    abstract = {This article addresses the augmentation of existing building models by a-priori not observable structures such as electric installations. The aim is to unambiguously
determine an electric network in an incremental manner with a minimum number of local measurements, e.g. using wire detectors, by suggesting the next measurement.
Different reasoning strategies, e.g. utilizing graph-theoretical algorithms, have been presented and tested based on a hypothesis which is generated using Mixed Integer
Linear Programming (MILP) while incorporating standards regarding the installation of electric wiring and findings from previous measurements. The presented
method has been successfully applied on simulated and real-world buildings, it saves up to 80% of the necessary measurements compared to an exhaustive verification
of the whole existing electric network, and paves the way for efficiently extending existing models, e.g. GIS models, with information on hidden utilities. This opens
up new opportunities to model further infrastructures, e.g. water pipes, in future research.},
    author = {Dehbi, Youness and Knechtel, Julius and Niedermann, Benjamin and Haunert, Jan-Henrik},
    doi = {10.1016/j.autcon.2022.104571},
    journal = {Automation in Construction},
    pages = {104571},
    title = {Incremental Constraint-based Reasoning for Estimating As-built Electric Line Routing in Buildings},
    volume = {143},
    year = {2022}
}

The objective of disaster scenes is to share location-based risk information to a large audience in an effective and intuitive way. However, current studies on three-dimensional (3D) representation for dam-break floods have the following limitations: (1) they are lacking a reasonable logic to organize the whole process of dam-break floods, (2) they present information in a way that cannot be easily understood by laypersons. Geospatial storytelling helps to create exciting experiences and to explain complex relationships of geospatial phenomena. This article proposes a three-dimensional virtual representation method for the whole process of dam-break floods from a geospatial storytelling perspective. The creation of a storyline and a storytelling-oriented representation of dam-break floods are discussed in detail. Finally, a prototype system based on WebGL is developed to conduct an experiment analysis. The results of the experiment show that the proposed method can effectively support 3D representation of the spatiotemporal process of dam-break floods. Furthermore, the statistical results indicate that the storytelling is useful for assisting participants in understanding the occurrence and development of dam-break floods, and is applicable to the popularization of disaster science for the general public.

doi:10.1080/17538947.2022.2118877

@article{li2022storytelling,
    abstract = {The objective of disaster scenes is to share location-based risk information to a large audience in an effective and intuitive way.
However, current studies on three-dimensional (3D) representation for dam-break floods have the following limitations: (1) they are lacking a reasonable logic to organize the whole process of dam-break floods,
(2) they present information in a way that cannot be easily understood by laypersons. Geospatial storytelling helps to create exciting experiences and to explain complex relationships of geospatial phenomena.
This article proposes a three-dimensional virtual representation method for the whole process of dam-break floods from a geospatial storytelling perspective.
The creation of a storyline and a storytelling-oriented representation of dam-break floods are discussed in detail. Finally, a prototype system based on WebGL is developed to conduct an experiment analysis.
The results of the experiment show that the proposed method can effectively support 3D representation of the spatiotemporal process of dam-break floods.
Furthermore, the statistical results indicate that the storytelling is useful for assisting participants in understanding the occurrence and development of
dam-break floods, and is applicable to the popularization of disaster science for the general public.},
    author = {Weilian, L. and Jun, Z. and Haunert, J.-H. and Lin, F. and Qing, Z. and Dehbi, Y.},
    doi = {10.1080/17538947.2022.2118877},
    journal = {International Journal of Digital Earth},
    pages = {1637--1656},
    title = {Three-dimensional virtual representation for the whole process of dam-break floods from a geospatial storytelling perspective},
    volume = {15},
    year = {2022}
}

doi:10.4230/LIPIcs.SoCG.2022.7

@inproceedings{arutyunovaDHHKL22,
    author = {Anna Arutyunova and
Anne Driemel and
Jan{-}Henrik Haunert and
Herman J. Haverkort and
J{\"{u}}rgen Kusche and
Elmar Langetepe and
Philip Mayer and
Petra Mutzel and
Heiko R{\"{o}}glin},
    booktitle = {Proc. 38th International Symposium on Computational Geometry (SoCG 2022)},
    doi = {10.4230/LIPIcs.SoCG.2022.7},
    pages = {7:1--7:18},
    publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"{u}}r Informatik},
    series = {LIPIcs},
    title = {Minimum-Error Triangulations for Sea Surface Reconstruction},
    url = {https://doi.org/10.4230/LIPIcs.SoCG.2022.7},
    volume = {224},
    year = {2022}
}

Building footprints are a prerequisite for many tasks such as urban mapping and planning. Such structures are mostly derived using airborne laser scanning which reveals rather roof structures than the underlying hidden footprint boundary. This paper introduces an approach to extract a 2D building boundary from a 3D point cloud stemming from either terrestrial scanning or via close-range sensing using a mobile platform, e.g. drone. To this end, a pipeline of methods including non-parametric kernel density estimation (KDE) of an underlying probability density function, a solution of the Travelling Salesperson Problem (TSP), outlier elimination and line segmentation are presented to extract the underlying building footprint. KDE turns out to be suitable to automatically determine a horizontal cut in the point cloud. An ordering of the resulting points in this cut using a shortest possible tour based on TSP allows for the application of existing line segmentation algorithms, otherwise dedicated to indoor segmentation. Outliers in the resulting segments are removed using DBSCAN. The segments are then generalized leading to the final footprint geometry. We applied our approach on real-world examples and achieved an IoU between 0.930 and 0.998 assessed by ground truth footprints from both authoritative and VGI data.

doi:10.5194/isprs-annals-X-4-W2-2022-233-2022

@article{rottmann2022AutomaticBuilding,
    abstract = {Building footprints are a prerequisite for many tasks such as urban mapping and planning. Such structures are mostly derived using
airborne laser scanning which reveals rather roof structures than the underlying hidden footprint boundary. This paper introduces an
approach to extract a 2D building boundary from a 3D point cloud stemming from either terrestrial scanning or via close-range sensing
using a mobile platform, e.g. drone. To this end, a pipeline of methods including non-parametric kernel density estimation (KDE)
of an underlying probability density function, a solution of the Travelling Salesperson Problem (TSP), outlier elimination and line
segmentation are presented to extract the underlying building footprint. KDE turns out to be suitable to automatically determine a
horizontal cut in the point cloud. An ordering of the resulting points in this cut using a shortest possible tour based on TSP allows for
the application of existing line segmentation algorithms, otherwise dedicated to indoor segmentation. Outliers in the resulting segments
are removed using DBSCAN. The segments are then generalized leading to the final footprint geometry. We applied our approach on
real-world examples and achieved an IoU between 0.930 and 0.998 assessed by ground truth footprints from both authoritative and
VGI data.},
    author = {Peter Rottmann and Jan-Henrik Haunert and Youness Dehbi},
    doi = {10.5194/isprs-annals-X-4-W2-2022-233-2022},
    journal = {ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences},
    pages = {233--240},
    title = {Automatic Building Footprint extraction from 3D laserscans},
    volume = {X-4/W2-2022},
    year = {2022}
}

@inproceedings{gedicke2022labelplacement,
    address = {Bonn},
    author = {Sven Gedicke and Adalat Jabrayilov and Benjamin Niedermann and Petra Mutzel and Jan-Henrik Haunert},
    booktitle = {Abstracts of 1st Workshop on Computational Cartography 2022},
    month = {may},
    title = {Point Feature Label Placement for Multi-Page Maps on Small-Screen Devices},
    year = {2022}
}

@inproceedings{rottmann2022mosaicsets_compcart,
    address = {Bonn},
    author = {Peter Rottmann and Makus Wallinger and Annika Bonerath and Sven Gedicke and Martin Nöllenburg and Jan-Henrik Haunert},
    booktitle = {Abstracts of 1st Workshop on Computational Cartography 2022},
    month = {may},
    title = {{M}osaic{S}ets: {E}mbedding {S}et {S}ystems into {G}rid {G}raphs},
    year = {2022}
}

Visualizing sets of elements and their relations is an important research area in information visualization. In this paper, we present MosaicSets : a novel approach to create Euler-like diagrams from non-spatial set systems such that each element occupies one cell of a regular hexagonal or square grid. The main challenge is to find an assignment of the elements to the grid cells such that each set constitutes a contiguous region. As use case, we consider the research groups of a university faculty as elements, and the departments and joint research projects as sets. We aim at finding a suitable mapping between the research groups and the grid cells such that the department structure forms a base map layout. Our objectives are to optimize both the compactness of the entirety of all cells and of each set by itself. We show that computing the mapping is NP-hard. However, using integer linear programming we can solve real-world instances optimally within a few seconds. Moreover, we propose a relaxation of the contiguity requirement to visualize otherwise non-embeddable set systems. We present and discuss different rendering styles for the set overlays. Based on a case study with real-world data, our evaluation comprises quantitative measures as well as expert interviews.

doi:10.1109/TVCG.2022.3209485

@article{rottmann2022mosaicsets,
    abstract = {Visualizing sets of elements and their relations is an important research area in information visualization. In this paper, we present MosaicSets : a novel approach to create Euler-like diagrams from non-spatial set systems such that each element occupies one cell of a regular hexagonal or square grid. The main challenge is to find an assignment of the elements to the grid cells such that each set constitutes a contiguous region. As use case, we consider the research groups of a university faculty as elements, and the departments and joint research projects as sets. We aim at finding a suitable mapping between the research groups and the grid cells such that the department structure forms a base map layout. Our objectives are to optimize both the compactness of the entirety of all cells and of each set by itself. We show that computing the mapping is NP-hard. However, using integer linear programming we can solve real-world instances optimally within a few seconds. Moreover, we propose a relaxation of the contiguity requirement to visualize otherwise non-embeddable set systems. We present and discuss different rendering styles for the set overlays. Based on a case study with real-world data, our evaluation comprises quantitative measures as well as expert interviews.},
    author = {Peter Rottmann and Makus Wallinger and Annika Bonerath and Sven Gedicke and Martin Nöllenburg and Jan-Henrik Haunert},
    doi = {10.1109/TVCG.2022.3209485},
    journal = {IEEE Transactions on Visualization and Computer Graphics},
    number = {1},
    pages = {875-885},
    publisher = {IEEE},
    title = {MosaicSets: Embedding set systems into grid graphs},
    volume = {29},
    year = {2022}
}

@inproceedings{bonerath2022thetastructure,
    address = {Bonn},
    author = {Annika Bonerath and Benjamin Niedermann and Jim Diederich and Yu Dong and Yannick Orgeig and Johannes Oehrlein and Jan-Henrik Haunert},
    booktitle = {Abstracts of 1st Workshop on Computational Cartography 2022},
    month = {may},
    title = {Theta Structure: A Time-Windowed Data Structure for the Spatial Visualization of Event Densities},
    year = {2022}
}

doi:10.5194/ica-abs-5-96-2022

@article{bonerath2022spatiotemporal,
    address = {Vienna},
    author = {Bonerath, Annika and Temerowski, Lukas and Gedicke, Sven and Haunert, Jan-Henrik},
    doi = {10.5194/ica-abs-5-96-2022},
    journal = {Abstracts of the ICA},
    month = {sep},
    pages = {96},
    title = {{E}xploring {S}patio-{T}emporal {E}vent {D}ata on a {S}mart {W}atch},
    volume = {5},
    year = {2022}
}

doi:10.5194/ica-abs-5-89-2022

@article{korir2022modalsplit,
    address = {Vienna},
    author = {Korir, Victor and Forsch, Axel and Dehbi, Youness and Haunert, Jan-Henrik},
    doi = {10.5194/ica-abs-5-89-2022},
    journal = {Abstracts of the ICA},
    month = {sep},
    pages = {89},
    title = {Visualizing the Modal Split in Public Transportation Networks},
    volume = {5},
    year = {2022}
}

Ever since location-based services and mobile applications collecting data gathered through Global Navigation Satellite System (GNSS) positioning have become popular, concerns about location privacy have been expressed. Research has shown that human trajectory repositories containing sequences of observed locations ordered in time constitute a rich source for analyzing movement patterns, but they can also reveal sensitive personal information, such as a person’s home address. In this paper, we present a mechanism that protects visits to sensitive locations by suppressing revealing parts of trajectories. Our attack model acknowledges that the course of a trajectory, combined with spatial context information, can facilitate privacy breaches even if sensitive locations have been concealed. Thus, we introduce the concept of k-site-unidentifiability, a specialization of k-anonymity, under which a sensitive location cannot be singled out from a group of at least k sites that the trajectory could have visited. In an experimental study, we show that our method is utility-preserving and protects sensitive locations reliably even in sparsely built environments. As it can process each trajectory independently, individuals may also use our mechanism to enhance their privacy before publishing their trajectories.

doi:10.1080/13658816.2022.2081694

@article{brauer2022myhome,
    abstract = {Ever since location-based services and mobile applications collecting data gathered through Global Navigation Satellite System (GNSS) positioning have become popular, concerns about location privacy have been expressed. Research has shown that human trajectory repositories containing sequences of observed locations ordered in time constitute a rich source for analyzing movement patterns, but they can also reveal sensitive personal information, such as a person’s home address. In this paper, we present a mechanism that protects visits to sensitive locations by suppressing revealing parts of trajectories. Our attack model acknowledges that the course of a trajectory, combined with spatial context information, can facilitate privacy breaches even if sensitive locations have been concealed. Thus, we introduce the concept of k-site-unidentifiability, a specialization of k-anonymity, under which a sensitive location cannot be singled out from a group of at least k sites that the trajectory could have visited. In an experimental study, we show that our method is utility-preserving and protects sensitive locations reliably even in sparsely built environments. As it can process each trajectory independently, individuals may also use our mechanism to enhance their privacy before publishing their trajectories.},
    author = {Anna Brauer and Ville M\"{a}kinen and Axel Forsch and Juha Oksanen and Jan-Henrik Haunert},
    doi = {10.1080/13658816.2022.2081694},
    eprint = {https://doi.org/10.1080/13658816.2022.2081694},
    journal = {International Journal of Geographical Information Science},
    number = {12},
    pages = {2496--2524},
    publisher = {Taylor \& Francis},
    title = {My home is my secret: concealing sensitive locations by context-aware trajectory truncation},
    url = {https://doi.org/10.1080/13658816.2022.2081694},
    volume = {36},
    year = {2022}
}

In the context of volunteered geographic information, large sets of trajectories of humans and animals are collected. Analyzing these trajectories visually is often complicated due to limited display sizes. For instance, when a user chooses a large map scale to inspect the details of a trajectory, only a small part of the trajectory is visible in the map. Therefore, in this article, we present an approach for visualizing the off-screen evolution of trajectories, i.e., their continuation outside of the displayed map. We propose visual cues in the form of glyphs that are displayed at the map's boundary and that consist of one or multiple disk sectors of varying size and opening angle. These glyphs indicate the direction and variability of direction of a trajectory's continuation outside the map frame. We present an algorithm for computing the glyphs efficiently and evaluate them in a user study. The results show that the glyphs are intuitive to understand even without explanation. We further present suggestions for improving the glyph design based on the results.

doi:10.1007/s42489-022-00106-6

@article{forsch2022offscreen,
    abstract = {In the context of volunteered geographic information, large sets of trajectories of humans and animals are collected. Analyzing these trajectories visually is often complicated due to limited display sizes. For instance, when a user chooses a large map scale to inspect the details of a trajectory, only a small part of the trajectory is visible in the map. Therefore, in this article, we present an approach for visualizing the off-screen evolution of trajectories, i.e., their continuation outside of the displayed map. We propose visual cues in the form of glyphs that are displayed at the map's boundary and that consist of one or multiple disk sectors of varying size and opening angle. These glyphs indicate the direction and variability of direction of a trajectory's continuation outside the map frame. We present an algorithm for computing the glyphs efficiently and evaluate them in a user study. The results show that the glyphs are intuitive to understand even without explanation. We further present suggestions for improving the glyph design based on the results.},
    author = {Forsch, Axel and Amann, Friederike and Haunert, Jan-Henrik},
    day = {18},
    doi = {10.1007/s42489-022-00106-6},
    issn = {2524-4965},
    journal = {KN - Journal of Cartography and Geographic Information},
    month = {May},
    number = {3},
    pages = {201--212},
    title = {Visualizing the Off-Screen Evolution of Trajectories},
    volume = {72},
    year = {2022}
}

Travel-time maps are an important tool for analyzing the efficacy of public transportation systems. These maps display one or multiple isochrones. An isochrone is a line of equal travel time, which means that reaching any point on it from a given starting point requires the same amount of time. As timetables are usually very irregular over the course of a week, travel-time maps are highly variant with respect to the starting time. Thus, for an extensive analysis of the network, this variance has to be visualized appropriately. One way of doing this is by using a digital map with animated transitions between different isochrones, so called morphs. In this work, we present an algorithm for computing such morphs between isochrones, particularly targeting schematized travel-time maps as they are often used for visualization in the context of public transportation. In our current research, we are optimizing the morphing between two given polygonal lines. In future research we plan to extend the approach to finding the correct polygon correspondences in the given isochrones.

@inproceedings{forsch2022morphing,
    abstract = {Travel-time maps are an important tool for analyzing the efficacy of public transportation systems. These maps display one or multiple isochrones. An isochrone is a line of equal travel time, which means that reaching any point on it from a given starting point requires the same amount of time. As timetables are usually very irregular over the course of a week, travel-time maps are highly variant with respect to the starting time. Thus, for an extensive analysis of the network, this variance has to be visualized appropriately. One way of doing this is by using a digital map with animated transitions between different isochrones, so called morphs. In this work, we present an algorithm for computing such morphs between isochrones, particularly targeting schematized travel-time maps as they are often used for visualization in the context of public transportation. In our current research, we are optimizing the morphing between two given polygonal lines. In future research we plan to extend the approach to finding the correct polygon correspondences in the given isochrones.},
    address = {Bochum},
    author = {Forsch, Axel and Kemna, Ruben and Langetepe, Elmar and Haunert, Jan-Henrik},
    booktitle = {3rd Schematic Mapping Workshop},
    month = {apr},
    note = {Poster abstract. Available at: https://www.ruhr-uni-bochum.de/schematicmapping/papers/smw-fklh.pdf},
    title = {Morphing of Schematized Polygons for Animated Travel-Time Maps},
    year = {2022}
}

Terrestrial laser scanning has become more and more popular in recent years. The according planning of the standpoint network is a crucial issue influencing the overhead and the resulting point cloud. Fully static approaches are both cost and time extensive, whereas fully kinematic approaches cannot produce the same data quality. Stop-and-go scanning, which combines the strengths of both strategies, represents a good alternative solution. In the scanning process, the standpoint planning is by now mostly a manual process based on expert knowledge and relying on the surveyor's experience. This paper provides a method based on Mixed Integer Linear Programming (MILP) ensuring an optimal placement of scanner standpoints considering all scanner-related constraints (e.g. incidence angle), a full coverage of the scenery, a sufficient overlap for the subsequent registration and an optimal route planning solving a Traveling Salesperson Problem (TSP). This enables the fully automatic application of autonomous systems for providing a complete model while performing a stop-and-go laser scanning, e.g. with the Spot robot from Boston Dynamics. Our pre-computed solution, i.e. standpoints and trajectory, has been evaluated surveying a real-world environment and successfully compared with a precise LoD2 building model of the underlying scene. The performed ICP-based registration issued from our fully automatic pipeline turns out to be a very good and safe alternative of the otherwise laborious target-based registration.

doi:10.5194/isprs-annals-V-4-2022-129-2022

@article{knechtel2022OptimalPositionPath,
    abstract = {Terrestrial laser scanning has become more and more popular in recent years.
The according planning of the standpoint network is a crucial issue influencing the overhead and the resulting point cloud. Fully static approaches are both cost and time extensive, whereas fully kinematic approaches cannot produce the same data quality.
Stop-and-go scanning, which combines the strengths of both strategies, represents a good alternative solution. In the scanning process, the standpoint planning is by now mostly a manual process based on expert knowledge and relying on the surveyor's experience. This paper provides a method based on Mixed Integer Linear Programming (MILP) ensuring an optimal placement of scanner standpoints considering all scanner-related constraints (e.g. incidence angle),
a full coverage of the scenery, a sufficient overlap for the subsequent registration and an optimal route planning solving a Traveling Salesperson Problem (TSP). This enables the fully automatic application of autonomous systems for providing a complete model while performing a stop-and-go laser scanning, e.g. with the Spot robot from Boston Dynamics.
Our pre-computed solution, i.e. standpoints and trajectory, has been evaluated surveying a real-world environment and successfully compared with a precise LoD2 building model of the underlying scene. The performed ICP-based registration issued from our fully automatic pipeline turns out to be a very good and safe alternative of the otherwise laborious target-based registration.},
    author = {Knechtel, Julius and Klingbeil, Lasse and Haunert, Jan-Henrik and Dehbi, Youness},
    doi = {10.5194/isprs-annals-V-4-2022-129-2022},
    journal = {ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences},
    pages = {129--136},
    title = {Optimal position and path planning for stop-and-go laserscanning for the acquisition of 3D building models},
    url = {https://www.isprs-ann-photogramm-remote-sens-spatial-inf-sci.net/V-4-2022/129/2022/},
    volume = {V-4-2022},
    year = {2022}
}

The complexity of disasters creates a significant challenge in the knowledge acquisition of the public. With the development of geospatial technologies, maps, geographic information science (GIS), and virtual geographic environment (VGE) are widely used to represent disaster information and help the public better understand disaster risk. However, the application, design, and specific challenges have not been investigated comprehensively in disaster information representation thus far. This article presents the weaknesses and strengths of the existing methods for representing disaster information in the last decades, and then the authors contribute some basic ideas for efficient disaster knowledge communication. The objective of this paper is to provide a clear image that improves users’ understanding of disaster information and bridge the communication gaps in disaster management. Finally, we suggest readers applying further creative thinking strategies to address the challenges associated with communicating disaster knowledge.

doi:10.1111/tgis.12922

@article{dehbi2020improving,
    abstract = {The complexity of disasters creates a significant challenge in the knowledge acquisition of the public.
With the development of geospatial technologies, maps, geographic information science (GIS), and virtual geographic environment (VGE) are widely used to represent disaster information and help the public better
understand disaster risk. However, the application, design, and specific challenges have not been investigated comprehensively in disaster information representation thus far.
This article presents the weaknesses and strengths of the existing methods for representing disaster information in the last decades, and then the authors contribute some basic ideas for efficient disaster knowledge communication.
The objective of this paper is to provide a clear image that improves users’ understanding of disaster information and bridge the communication gaps in disaster management.
Finally, we suggest readers applying further creative thinking strategies to address the challenges associated with communicating disaster knowledge.},
    author = {Li, W. and Zhu, J. and Pirasteh, S. and Zhu, Q. and Fu, L. and Wu, J. and Hu, Y. and Dehbi, Y.},
    doi = {10.1111/tgis.12922},
    eprint = {https://onlinelibrary.wiley.com/doi/pdf/10.1111/tgis.12922},
    journal = {Transactions in GIS},
    number = {3},
    pages = {1376-1398},
    title = {Investigations of disaster information representation from a geospatial perspective: progress, challenges and recommendations},
    url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/tgis.12922},
    volume = {26},
    year = {2022}
}