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The paper presents a new algorithm to reconstruct elongated objects defined by cross sections and trajectories in gridded threedimensional models represented as voxels. Examples of such objects are the elements of underground infrastructure in urban environments, such as pipes, conduits and tunnels. Starting from a basic methodology, which is based on distance transformations, the algorithm is extended in three ways on the basis of Voronoi datasets being produced alongside. [ABSTRACT FROM AUTHOR]

The paper presents a very straightforward and effective algorithm to convert a space partitioning, made up of polyhedral objects, into a 3D block of voxels, which is fully occupied, i.e. in which every voxel has a value. In addition to walls, floors, etc. there are 'air' voxels, which in turn may be distinguished as indoor and outdoor air. The method is a 3D extension of a 2D polygon-to-raster conversion algorithm. The input of the algorithm is a set of non-overlapping, closed polyhedra, which can be nested or touching. The air volume is not necessarily represented explicitly as a polyhedron (it can be treated as 'background', leading to the 'default' voxel value). The approach consists of two stages, the first being object (boundary) based, the second scan-line based. In addition to planar faces, other primitives, such as ellipsoids, can be accommodated in the first stage without affecting the second. [ABSTRACT FROM AUTHOR]

The European FP7 project IQmulus yearly organizes several processing contests, where submissions are requested for novel algorithms for point cloud and other big geodata processing. This paper describes the set-up and execution of a contest having the purpose to evaluate state-of-the-art algorithms for Mobile Mapping System point clouds, in order to detect and identify (individual) trees. By the nature of MMS these are trees in the vicinity of the road network (rather than in forests). Therefore, part of the challenge is distinguishing between trees and other objects, such as buildings, street furniture, cars etc. Three submitted segmentation and classification algorithms are thus evaluated. [ABSTRACT FROM AUTHOR]

Change detection on the basis of multi-temporal imagery may lead to false alarms when the image has changed, whereas the scene has not. Geometric image differerences in an unchanged scene may be due to relief displacement, caused by diferent camera positions. Radiometric differences may be caused by changes in illumimation and shadow between the images, caused by a different position of the sun. The effects may be predicted, and after that compensated, if a 3d model of the scene is available. The paper presents an integrated approach to prediction of and compensation for relief displacement, shading and shadow. [ABSTRACT FROM AUTHOR]