Cityscapes provide a complex environment, where solar radiation is unevenly distributed, especially since urban features started to propagate more and more vertically. Due to the dynamic overshadowing effects present on building surfaces, quantifying these phenomena is essential for predicting reductions in solar radiation availability that can significantly affect potential for solar energy use. Numerical radiation algorithms coupled with GIS tools are a pathway to evaluate those complex effects. Accurate representation of the terrain, vegetation canopy and building structures allows better estimation of shadow patterns. Higher spatial and temporal resolutions deliver more detailed results, but models must compromise between accuracy and computation time. In this paper, models ranging from simple 2D visualization and solar constant methods, to more sophisticated 3D representation and analysis, are reviewed. Web-based solar maps, which rely on the previous features to successfully communicate the benefits of the solar resource to the public and support in the policy-making process, are also addressed.

Modelling solar potential in the urban environment: State-of-the-art review

Spatial data mining fulfils real needs of many geomatic applications. It allows the geomatics community to take advantage of the growing availability of geographically referenced data and benefit from this rich information resource. This article addresses spatial data classification for using decision trees. A new method called SCART which differs from conventional decision trees by considering the specifics of geographical data, namely their organisation in thematic layers, and their spatial relationships is proposed. SCART is an extension of CART methods in two ways. On the one hand, the algorithm considers several thematic layers as in the so-called relational data mining area, and on the other hand, it extends discriminating criteria to address concerns about the neighbourhood. As such, the algorithm determines which combination of attribute values and spatial relationships of neighbouring objects provide the best criterion.

Advances in Spatial Data Handling

Advances in storage management and visualization tools have expanded the frontiers of traditional 2D domains like GIS to 3Dimensions. Recent proposals such as CityGML and associated gateways bridge a long-standing gap between the terrestrial models from the GIS and the CAD/CAM worlds and shift the focus from 2D to 3D. As a result, efficient and scalable techniques for storage, validation and query of 3D models will become a key to terrestrial data management. In this paper, we focus on the problem of validation of 3D geometries. First we present Oracle’s data model for storing 3D geometries (following the general OGC/ISO GML3 specifications). Then, we define more specific and refined rules for valid geometries in this model. We show that the solid representation is simpler and easier to validate than the GML model but still retains the representative power. Finally, we present explicit examples of valid and invalid geometries. This work should make it to easy to conceptualize valid and invalid 3D geometries.

On Valid and Invalid Three-Dimensional Geometries

In this paper, we propose an original framework for description and matching of three dimensional faces for recognition purposes. Basic traits of a face are encoded by extracting iso-geodesic stripes from the surface of a face model. A compact representation is then constructed through a modeling technique capable to express the basic shape of iso-geodesic stripes and quantitatively measure their spatial relationships in a three dimensional space. This information is encoded in an attributed relational graph. In this way,the structural similarity between two face models is evaluated by matching their corresponding graphs.Experimental results on a 3D face database and baseline comparison show that the proposed solution attains high face recognition accuracy and is reasonably robust to facial expression and pose changes.

Description and retrieval of 3D face models using iso-geodesic stripes

The 9+-intersection is an extension of the 9-intersection, which distinguishes the topological relations between various spatial objects by the pattern of a nested matrix. This paper develops a small set of constraints on this matrix, which is applicable to arbitrary pairs of spatial objects in various spaces. Based on this set of universal constraints, the sets of matrix patterns, each representing a candidate for topological relations, are derived for every possible pair of basic objects (points, directed/non-directed line segments, regions, and bodies) embedded in R 1, R 2, R 3, S 1, and S 2. The derived sets of candidates are consistent with the sets of topological relations ever identified, as well as yield the identification of some missing sets of topological relations. Finally, the topological relations between a region and a region with a hole in R 2and S 2are identified to demonstrate the applicability of our approach to deriving topological relations between more complicated objects.

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The 9 + -Intersection: A Universal Framework for Modeling Topological Relations

This paper presents an integrated study on the possible topological relationship between multidimensional simple objects in 0, 1, 2 and 3D space. The formal categorisation of spatial relationships is completed upon the 9-intersections model. The focus is on the definition of a unified set of conditions for eliminating relationships that cannot be realised in reality. The negative conditions are formulated on the basis of dimension and co-dimension of objects, and connectivity of boundaries. The set of 25 conditions is sufficient for deriving all the possible relationships mentioned currently in the literature and for specifying the relationships between surface and surface in 3D space. Drawings of example configurations verify the obtained results in 3D space.

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S. Zlatanova

Papers

On 3D topological relationships