Computing watertight volumetric models from boundary representations to ensure consistent topological operations

To simulate environmental processes, noise, flooding in cities as well as the behaviour of buildings and infrastructure, ‘watertight’ volumetric models are a measuring prerequisite. They ensure topologically consistent 3D models and allow the definition of proper topological operations. However, in many existing city or other geo-information models, topologically unchecked boundary representations are used to store spatial entities. In order to obtain consistent topological models, including their ‘fillings’, in this paper, a triangulation combined with overlay and path-finding methods is presented by climbing up the dimension, beginning with the wireframe model. The algorithms developed for this task are presented, whereby using the philosophy of graph databases and the Property Graph Model. Examples to illustrate the algorithms are given, and experiments are performed on a data-set from Erfurt, Thuringia (Germany), providing complex geometries of buildings. The heavy influence of double precision arithmetic on the results, in particular the positional and angular precision, is discussed in the end

Absolute quantification of cohesin, CTCF and their regulators in human cells.

The organisation of mammalian genomes into loops and topologically associating domains (TADs) contributes to chromatin structure, gene expression and recombination. TADs and many loops are formed by cohesin and positioned by CTCF. In proliferating cells, cohesin also mediates sister chromatid cohesion, which is essential for chromosome segregation. Current models of chromatin folding and cohesion are based on assumptions of how many cohesin and CTCF molecules organise the genome. Here we have measured absolute copy numbers and dynamics of cohesin, CTCF, NIPBL, WAPL and sororin by mass spectrometry, fluorescence-correlation spectroscopy and fluorescence recovery after photobleaching in HeLa cells. In G1-phase, there are similar to 250,000 nuclear cohesin complexes, of which similar to 160,000 are chromatin-bound. Comparison with chromatin immunoprecipitation-sequencing data implies that some genomic cohesin and CTCF enrichment sites are unoccupied in single cells at any one time. We discuss the implications of these findings for how cohesin can contribute to genome organisation and cohesion

Iz časopisa

From the field of cartography and geoinformation, there are journal’s article extracts given which are not cartographic first and whose complete texts are on the Internet, accessible to the members of Croatian academic and research community. Most journals can be accessed through the PERO browser (http://knjiznica.irb.hr/pero/index.php).Dan je izbor članaka iz područja kartografije i geoinformacija iz časopisa, koji nisu u prvom redu kartografski, a kojima su cjeloviti tekstovi dostupni na internetu članovima hrvatske akademske i istraživačke zajednice. Većina časopisa dostupna je preko pretraživača PERO (http://knjiznica.irb.hr/pero/index.php)

The Evolution of 3D Printing in AEC: From Experimental to Consolidated Techniques

The chapter leads the reader through the historical development of additive manufacturing (AM) techniques until the most recent developments. A tentative taxonomy is added to the historical perspective, in order to better understand the main lines of development and the potential cross-fertilization opportunities. Some case studies are analyzed in order to provide a clearer picture of the practical applications of AM in architecture engineering and construction (AEC), with a particular attention to the use of AM for final products rather than just prototypes. Eventually, some thoughts are shared as to the impact of AM on AEC beyond the mere cost-effectiveness and well into the potential change of paradigms in how architecture can be thought of and further developed embracing the new world of opportunities brought by AM

Semantic enrichment of city information models with LiDAR-based rooftop albedo

In the era of smart city, semantically rich city information models (CIMs) are demanded as a critical information hub. Roof albedo, a semantic property measures how much solar radiation is reflected, is vital to various urban sustainability topics, including heat island, local climate, green roof, and urban morphology. This paper presents an approach that enriches LiDAR-based albedo to rooftop models for CIM. First, we apply Chen et al. (2018)’s method to the reconstruction of the geometries of rooftop elements. Then, albedos of roofs and rooftop elements are estimated from the mean reflectance in LiDAR data. A pilot study was conducted in an urban area in Hong Kong. The results showed that the building models created by the presented approach were satisfactory in terms of rooftop elements and roof albedos. The results from the present approach can provide sustainability study the details of 3D geometries and albedos in an urban area

MIGRATION OF DIGITAL CARTOGRAPHY TO CITYGML; A WEB-BASED TOOL FOR SUPPORTING SIMPLE ETL PROCEDURES

Abstract. Digital cartography is notably produced in all countries, in different scales and formats. Latest cartographic production aims at creating 3D objects with topological consistency and rich information linked by attribute tables, i.e. the principles behind data to be managed in geographic information systems (GIS) environments. These data contain all the information necessary for production of the first levels of detail (LOD) of the CityGML model. The work presented reports on the first steps for a guided workflow to upload cartographic data containing building footprints, heights and other information, and migrating it to a validated CityGML model. The steps include a web-portal for uploading the data in a compressed archive containing shapefiles, and a back-end Python script that reads coordinate vertices, attributes and other necessary information, and creates a CityGML file. The process was tested on the Italian topographic geodatabase of some of the main cities of Italy. Discussion on workflow steps and results are presented. Results show that this process is feasible and it can be used to facilitate first tests on transforming existing cartography to CityGML models, which can be then used for further analysis.</p

DETECTION AND EVALUATION OF TOPOLOGICAL CONSISTENCY IN CITYGML DATASETS

The topological consistency of Boundary-Representation models, meaning here that the incidence graph is homeomorphic with the underlying topology of geographical data, is checked for several CityGML datasets, and a first classification of topological inconsistencies is performed. The analysis is carried out on a spatial database system into which the datasets have been imported. It is found that real-world datasets contain many topologically inconsistent pairs of intersecting polygons. Also data satisfying the ISO/OGC standards can still be topologically inconsistent. In the case when the intersection is a point, topological inconsistency occurs because a vertex lies on a line segment. However, the most frequent topological inconsistencies seem to arise when the intersection of two polygons is a line segment. Consequently, topological queries in present CityGML data cannot rely on the incidence graph only, but must always make costly geometric computations if correct results are to be expected

Testing the Impact of 2D Generalisation on 3D Models – Exploring Analysis Options With an Off-the-shelf Software Package

Popularity and diverse use of 3D city models has increased exponentially in the past few years, providing a more realistic impression and understanding of cities. Often, 3D city models are created by elevating the buildings from a detailed 2D topographic base map and subsequently used in studies such as solar panel allocation, infrastructure remodelling, antenna installations or even tourist guide applications. However, the large amount of resulting data slows down rendering and visualisation of the 3D models, and can also impact the performance of any analysis. Generalisation enables a reduction in the amount of data – however the addition of the third dimension makes this process more complex, and the loss of detail resulting from the process will inevitably have an impact on the result of any subsequent analysis. While a few 3D generalization algorithms do exist in a research context, these are not available commercially. However, GIS users can create the generalised 3D models by simplifying and aggregating the 2D dataset first and then extruding it to the third dimension. This approach offers a rapid generalization process to create a dataset to underpin the impact of using generalised data for analysis. Specifically, in this study, the line of sight from a tall building and the sun shadow that it creates are calculated and compared, in both original and generalised datasets. The results obtained after the generalisation process are significant: both the number of polygons and the number of nodes are minimized by around 83% and the volume of 3D buildings is reduced by 14.87%. As expected, the spatial analyses processing times are also reduced. The study demonstrates the impact of generalisation on analytical results – which is particularly relevant in situations where detailed data is not available and will help to guide the development of future 3D generalisation algorithms. It also highlights some issues with the overall maturity of 3D analysis tools, which could be one factor limiting uptake of 3D GIS