Julien Perret

Conception of a GIS-Platform to simulate urban densification based on the analysis of topographic data

The aim of our research is to analyze the evolution of urbanization and to simulate it on specific areas. We focus on the evolution between 1950 and now. We analyse the densification by means of comparing temporal topographic data bases created from existing topographic data base and maps and photo from 1950. In this paper we present how a simulation works - which input data are used, which functions are used to densify the space and how the simulation works, is tuned and run - the densification method for each urban block illustrated with results, the method used during the project to build the required knowledge for simulation and we conclude and present the main research perspectives. The methods are implemented on a dedicated open source software named GeOpenSim.

A Stochastic Method for the Generation of Optimized Building Layouts Respecting Urban Regulations

The development in an urban area normally has to obey planning regulations. In France, such regulations are specified in local urban planning schemes (LUPS or PLU in French) defining the right to build at municipal or inter-municipal level. Many aspects are concerned in a PLU. We address to the spatial aspect defining the rules for building development. Since these rules are stated in technical documents, it’s not easy to comprehend or to assess their impacts. Driven by such issues, we propose to generate 3D building layouts that comply with the rules and have optimized indicators (e.g. floor area ratio), which is optional but useful. A building layout is a configuration of a number of buildings with various shapes (simplified as 3D boxes in this work). Thus, it can be seen as a realization of a marked point process (MPP) of 3D boxes, whose probability distribution can be defined through Gibbs energy with regard to a reference process. Its energy component reflects the compliance with the PLU rules in our problem. By maximizing this probability the optimal building layout can be found. The optimization task is realized by trans-dimensional simulated annealing (TDSA) coupled with a Reversible Jump Markov Chain Monte Carlo (RJMCMC) sampler. Several common types of the French PLU rules are studied and modeled into energy terms, and a case study is conducted to validate our approach.

Stochastic Buildings Generation to Assist in the Design of Right to Build Plans

The design of documents impacting potential new constructions, such as Right to Build plans, is a complex issue. New tools need to be proposed in order to systematically assess the impact of regulations on the building potential of the concerned areas. Furthermore, it is often not directly the morphology of new constructions that administrations and citizens would like to regulate but their properties with regard to other phenomena (solar energy potential, etc.). In order to tackle these issues, we propose in this article to explore building configurations and regulations using a stochastic building generator and a workflow engine. The workflow we propose for such an exploration will produce important amounts of data that we intend to release as OpenData in order for administrations, urban planners and citizens to be able to freely visualize and collectively choose the regulations that best suit their territory. Such amount of 3D geographical data also suggests new issues in geovisualization.

3D urban data to assess local urban regulation influence

Abstract Systematically assessing the influence of new urban plans is an important challenge for designing them efficiently. In this paper, we propose a method to assess the influence of local ‘Right to Build’ regulations on constructibility. Our method is based on an optimization algorithm that generates building configurations. This method requires a geographic model that supports the formalization of the Right to Build regulation in order to check if a building respects it. The proposed approach relies on the trans-dimensional simulated annealing optimization method, which produces building configurations composed of a set of parametric objects (boxes in our implementation). Our proposition is released as the SimPLU3D Open-Source project ( http://ignf.github.io/simplu3D/ ). In this paper, we present some tests and results based on this implementation and a use related to the assistance to ‘Right to Build’ designers.

2D Arrangement-based Hierarchical Spatial Partitioning: An Application to Pedestrian Network Generation

This paper addresses the creation and maintenance of partitions of city surfaces for mapping and transportation applications. It proposes a hierarchical spatial surface partitioning, encoding the spatial partition with a 2D arrangement and structuring a generic hierarchy of semantic objects with a directed acyclic graph (DAG), in which the leaves point to the partition elements (polygonal regions, line strings, points). Semantic objects such as buildings, sidewalks and roads are described by grouping other objects and partition elements with their semantic relationships. In the proposed generic data model, geometry and spatial relationships of the semantic objects are respectively described by the geometry and topology of the planar partition. The proposed geometric data structure for creating and maintaining this partition is a 2D arrangement. In addition, the hierarchical object model encodes the thematic and semantic relationships between the objects. Besides the data model, methods and algorithms are discussed for leveraging existing vector datasets to create and maintain such partitions. These partitions are then fit to further processing and analysis using computational geometry and graph theory algorithms. For this purpose, three application-wise generic algorithms were integrated into our system called Streetmaker: two skeleton operators for centerline generation (straight skeleton and medial axis) and connectivity graphs for itinerary calculations. Moreover, specific algorithms can be integrated into Streetmaker for specific applications. We demonstrated an example usage of this framework for generating static obstacle avoiding pedestrian network graphs. The representation of the network graph and the process used to generate it, can be considered as the second contribution of our work besides the proposed data model.

Assessing the planimetric accuracy of Paris atlases from the late 18th and 19th centuries

The recent initiatives to digitize cultural heritage resources and publish them on the Web have renewed interest in historical maps for the diachronic analysis of territories in GIS applications. However, such analyses should not be done without a good understanding of the possibilities and limitations of geographical information provided by historical maps, i.e. their quality. One of the major concerns regarding historical maps quality is their positional planimetric accuracy which highly depends on survey techniques used at the time. As these techniques are not always thoroughly known and as ground truth is most of the time not sufficiently available, direct absolute evaluation approaches have been proposed to assess historical maps positional planimetric accuracy. In this article, we follow the intuition that the most widely adopted georeferencing-based approach for assessing the positional planimetric accuracy of historical maps can be adapted to provide an evaluation of the error caused by the survey process in cases like Paris atlases where the georeferencing transformation can be estimated with ground control points based on geodetic features and where the projection of the map can be approximated by a well known projected coordinate reference system. We apply this tuned approach on the Verniquet atlas and evaluate the validity of our hypothesis about projection approximation.