Hochschule für Architektur, Bau und Geomatik FHNW
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Publikation (Near) real-time snow water equivalent observation using GNSS refractometry and RTKLIB(MDPI, 2022) Steiner, Ladina; Studemann, Géraldine Laurence; Grimm, David; Marty, Christoph; Leinss, SilvanGlobal navigation satellite system (GNSS) refractometry enables automated and continuous in situ snow water equivalent (SWE) observations. Such accurate and reliable in situ data are needed for calibration and validation of remote sensing data and could enhance snow hydrological monitoring and modeling. In contrast to previous studies which relied on post-processing with the highly sophisticated Bernese GNSS processing software, the feasibility of in situ SWE determination in post-processing and (near) real time using the open-source GNSS processing software RTKLIB and GNSS refractometry based on the biased coordinate Up component is investigated here. Available GNSS observations from a fixed, high-end GNSS refractometry snow monitoring setup in the Swiss Alps are reprocessed for the season 2016/17 to investigate the applicability of RTKLIB in post-processing. A fixed, low-cost setup provides continuous SWE estimates in near real time at a low cost for the complete 2021/22 season. Additionally, a mobile, (near) real-time and low-cost setup was designed and evaluated in March 2020. The fixed and mobile multi-frequency GNSS setups demonstrate the feasibility of (near) real-time SWE estimation using GNSS refractometry. Compared to state-of-the-art manual SWE observations, a mean relative bias below 5% is achieved for (near) real-time and post-processed SWE estimation using RTKLIB01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Implementation and first evaluation of an indoor mapping application using smartphones and frameworks(2019) Hasler, Oliver; Blaser, Stefan; Nebiker, StephanIn this paper, we present the implementation of a smartphone-based indoor mobile mapping application based on an augmented reality (AR) framework and a subsequent performance evaluation in demanding indoor environments. The implementation runs on Android and iOS devices and demonstrates the great potential of smartphone-based 3D mobile mapping. The application includes several functionalities such as device tracking, coordinate, and distance measuring as well as capturing georeferenced imagery. We evaluate our prototype system by comparing measured points from the tracked device with ground control points in an indoor environment with two different campaigns. The first campaign consists of an open, one-way trajectory whereas the second campaign incorporates a loop closure. In the second campaign, the underlying AR framework successfully recognized the start location and correctly repositioned the device. Our results show that the absolute 3D accuracy of device tracking with a standard smartphone is around 1% of the travelled distance and that the local 3D accuracy reaches sub-decimetre level.04B - Beitrag KonferenzschriftPublikation Open urban and forest datasets from a high-performance mobile mapping backpack. A contribution for advancing the creation of digital city twins(International Society of Photogrammetry and Remote Sensing, 2021) Blaser, Stefan; Meyer, Jonas; Nebiker, StephanWith this contribution, we describe and publish two high-quality street-level datasets, captured with a portable high-performance Mobile Mapping System (MMS). The datasets will be freely available for scientific use. Both datasets, from a city centre and a forest represent area-wide street-level reality captures which can be used e.g. for establishing cloud-based frameworks for infrastructure management as well as for smart city and forestry applications. The quality of these data sets has been thoroughly evaluated and demonstrated. For example, georeferencing accuracies in the centimetre range using these datasets in combination with image-based georeferencing have been achieved. Both high-quality multi sensor system street-level datasets are suitable for evaluating and improving methods for multiple tasks related to high-precision 3D reality capture and the creation of digital twins. Potential applications range from localization and georeferencing, dense image matching and 3D reconstruction to combined methods such as simultaneous localization and mapping and structure-from-motion as well as classification and scene interpretation. Our dataset is available online at: https://www.fhnw.ch/habg/bimage-datasets04B - Beitrag KonferenzschriftPublikation AI-based 3D detection of parked vehicles on a mobile mapping platform using edge computing(2022) Meyer, Jonas; Blaser, Stefan; Nebiker, StephanIn this paper we present an edge-based hardware and software framework for the 3D detection and mapping of parked vehicles on a mobile mapping platform for the use case of on-street parking statistics. First, we investigate different point cloud-based 3D object detection methods on our extremely dense and noisy depth maps obtained from low-cost RGB-D sensors to find a suitable object detector and determine the optimal preparation of our data. We then retrain the chosen object detector to detect all types of vehicles, rather than standard cars only. Finally, we design and develop a software framework integrating the newly trained object detector. By repeating the parking statistics of our previous work (Nebiker et al., 2021), our software is tested regarding the detection accuracy. With our edge-based framework, we achieve a precision and recall of 100% and 98% respectively on any parking configuration and vehicle type, outperforming all other known work on on-street parking statistics. Furthermore, our software is evaluated in terms of processing speed and volume of generated data. While the processing speed reaches only 1.9 frames per second due to limited computing resources, the amount of data generated is just 0.25 KB per frame.04B - Beitrag KonferenzschriftPublikation Do you see us? Applied visual analytics for the investigation of group coordination(Springer, 18.02.2019) Rack, Oliver; Zahn, Carmen; Bleisch, SusanneGroup coordination is a relevant prerequisite for understanding the effectiveness of groups. But, contrary to the large number of empirical studies, only a few studies concentrate on the development of analysis methods of coordination in groups. Hence, the purpose of this paper is to give a summary of the opportunities and limitations of common methods for capturing group coordination in applied field settings and to outline how visual analytics approaches might add to the common methods. Based on two illustrated visual analytics implementation examples—1) coordination and movements of soccer players, and 2) spatio-temporal event data—the potential of visual analytics approaches is identified for studying a greater variety of types of group coordination, and to consider the multifaceted nature of group processes in order to go beyond traditional coding processes.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Image-based orientation determination of mobile sensor platforms(International Society of Photogrammetry and Remote Sensing, 2021) Hasler, Oliver; Nebiker, StephanAbstract. Estimating the pose of a mobile robotic platform is a challenging task, especially when the pose needs to be estimated in a global or local reference frame and when the estimation has to be performed while the platform is moving. While the position of a platform can be measured directly via modern tachymetry or with the help of a global positioning service GNSS, the absolute platform orientation is harder to derive. Most often, only the relative orientation is estimated with the help of a sensor mounted on the robotic platform such as an IMU, with one or multiple cameras, with a laser scanner or with a combination of any of those. Then, a sensor fusion of the relative orientation and the absolute position is performed. In this work, an additional approach is presented: first, an image-based relative pose estimation with frames from a panoramic camera using a state-of-the-art visual odometry implementation is performed. Secondly, the position of the platform in a reference system is estimated using motorized tachymetry. Lastly, the absolute orientation is calculated using a visual marker, which is placed in the space, where the robotic platform is moving. The marker can be detected in the camera frame and since the position of this marker is known in the reference system, the absolute pose can be estimated. To improve the absolute pose estimation, a sensor fusion is conducted. Results with a Lego model train as a mobile platform show, that the trajectory of the absolute pose calculated independently with four different markers have a deviation < 0.66 degrees 50% of the time and that the average difference is < 1.17 degrees. The implementation is based on the popular Robotic Operating System ROS.04B - Beitrag KonferenzschriftPublikation Gaining overview with transient focus+context maps(Taylor & Francis, 2021) Hollenstein, Daria; Bleisch, SusanneGaining an overview of large spatial data sets presents a challenge common to various domains. 'Overviewing' spatial data involves viewing different areas of focus and context at different scales and requires access to detail from zoomed-out views. Standard pan and zoom interfaces provide limited support with this. Motivated by the application scenario of flood risk monitoring, we extend pan and zoom affordances with a combination of focus+context techniques and multiple maps to support 'overviewing' spatial data with a graph-like information structure. A combination of transient overlays to preview context-on-demand as well as detail-on-demand with the option to decouple additional maps enables fast navigation through the graph-like information space. User-created and -positioned, resizable multiple maps allow for simultaneous exploration of distant regions at flexible scales. The seamless integration of these concepts and the versatility of its components allow for continuously adaptable, user-defined layouts that support various analysis situations. We present a prototype implementation of this interaction model and illustrate its working in application to a hydrometric network, but we believe the model could be transferred to graph-like data in other domains.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Investigating roundabout properties and bicycle accident occurrence at Swiss roundabouts: A logistic regression approach(MDPI, 2019) Hollenstein, Daria; Hess, Martin; Jordan, Denis; Bleisch, SusanneThe positive effects of active mobility on mental and physical health as well as on air quality are widely acknowledged. Increasing the share of active travel is therefore an aim in many countries. Providing bicycle-safe infrastructure is one way to promote cycling. Roundabouts are a common traffic infrastructure and are supposed to facilitate safe and smooth traffic flow. However, data on road traffic accidents indicate an over-proportional involvement of cyclists in accidents at roundabouts. In the present study, the influence of roundabout geometry and traffic flow on bicycle accident occurrence was investigated using a logistic regression approach on twelve parameters of N = 294 mostly small- and mini-sized single-lane roundabouts in the Canton of Berne, Switzerland. Average weekday motorized traffic was identified as a major factor in explaining bicycle accident occurrence at roundabouts. Further, the radius of the central island, the location of the roundabout (in town vs. out of town) and the number of legs were significantly related to bicycle accident occurrence. While these results are in general agreement with findings from similar studies, the findings regarding the central island’s radius and the number of legs underpin the need for roundabout type-specific studies: Some parameters may not prove relevant in intermediate- to large-sized roundabouts, but become critical in small or mini roundabouts, which are common in Switzerland and numerous in the present sample.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Digital twinning of the built environment. An interdisciplinary topic for innovation in didactics(Copernicus, 2020) Wahbeh, Wissam; Kunz, Dominique; Hofmann, Joachim; Bereuter, PiaThe concept of a Digital Twin (DT) takes an increasingly important role in the construction industry and related research fields. It is a concept associated with Industry 4.0; however, the scientific literature does not provide a unique and clear definition of this concept. This paper aims to analyse the definitions of the digital twin to clarify this concept in the related fields of architecture, engineering and construction (AEC). Moreover, this work proposes and employs the concept of a Digital Twin as an objective for a project-based learning approach in a didactical setting. As an interdisciplinary approach, this work demonstrates the potential impact on the traditional didactical frameworks in the educational domain of construction and its value as an opportunity to introduce interdisciplinary expertise to all students in these fields. This work presents a use case applying the concept at the School of Architecture, Civil Engineering and Geomatics of FHNW.04B - Beitrag KonferenzschriftPublikation Toward flexible visual analytics augmented through smooth display transitions(Elsevier, 2021) Tominski, Christian; Andrienko, Gennady; Andrienko, Natalia; Bleisch, Susanne; Fabrikant, Sara Irina; Mayr, Eva; Miksch, Silvia; Pohl, Margit; Skupin, AndréVisualizing big and complex multivariate data is challenging. To address this challenge, we propose flexible visual analytics (FVA) with the aim to mitigate visual complexity and interaction complexity challenges in visual analytics, while maintaining the strengths of multiple perspectives on the studied data. At the heart of our proposed approach are transitions that fluidly transform data between user-relevant views to offer various perspectives and insights into the data. While smooth display transitions have been already proposed, there has not yet been an interdisciplinary discussion to systematically conceptualize and formalize these ideas. As a call to further action, we argue that future research is necessary to develop a conceptual framework for flexible visual analytics. We discuss preliminary ideas for prioritizing multi-aspect visual representations and multi-aspect transitions between them, and consider the display user for whom such depictions are produced and made available for visual analytics. With this contribution we aim to further facilitate visual analytics on complex data sets for varying data exploration tasks and purposes based on different user characteristics and data use contexts.01A - Beitrag in wissenschaftlicher Zeitschrift