Archive for the ‘Recent Publications’ Category

Evidence for amodal representations after bimodal learning: Integration of haptic-visual layouts into a common spatial image.

Sunday, January 3rd, 2010

Giudice, N. A., Klatzky, R. L., & Loomis, J. M. (in press). Evidence for amodal representations after bimodal learning: Integration of haptic-visual layouts into a common spatial image. Spatial Cognition & Computation.

Participants learned circular layouts of 6 objects presented haptically or visually, then indicated the direction from a start target to an end target of the same or different modality (intra-modal versus inter-modal). When objects from the two modalities were learned separately, superior performance for intra-modal trials indicated a cost of switching between modalities. When a bimodal layout intermixing modalities was learned, intra- and inter-modal trials did not differ reliably. These findings indicate that a spatial image, independent of input modality, can be formed when inputs are spatially and temporally congruent, but not when modalities are temporally segregated in learning.

Spatial learning and navigation using a virtual verbal display

Friday, January 1st, 2010

Giudice, N.A., Bakdash, J.Z., Legge, G.E., & Roy, R. (in press). Spatial learning and navigation using a virtual verbal display. ACM Transactions on Applied Perception.

We report on three experiments that investigate the efficacy of a new type of interface, called a virtual verbal display (VVD) for non-visual learning and navigation of computer-based virtual environments (VEs). Although verbal information has been studied for route-guidance, little is known about the use of context-sensitive, speech-based displays, e.g. the VVD, for supporting free exploration and wayfinding behavior. During training, participants used the VVD (Experiments I and II) or a visual display (Experiment III) to search the VEs and find four hidden target locations. At test, all participants performed a route-finding task in the corresponding real environment, navigating with vision (Experiments I and III) or from verbal descriptions (Experiment II). Training performance between virtual display modes was comparable, but wayfinding in the real environment was worse after VVD learning than visual learning, regardless of the testing modality. Our results support the efficacy of the VVD for searching computer-based environments but indicate a difference in the cognitive maps built up between verbal and visual learning, perhaps due to lack of physical movement in the VVD.

Topological Relations from Metric Refinements

Sunday, November 1st, 2009

Egenhofer, M. and M. Dube. Topological Relations from Metric Refinements. Proceedings of the 17th ACM SIGSPATIAL – International Conference on Advances in Geographic Information Systems, Seattle, WA. D. Agrawal, W. Aref, C. Lu, M. Mokbel, P. Scheuermann, C. Shahabi and O. Wolfson (eds.), November, 2009. pp. 158-167.

Abstract: Naive Geography’s premise “Topology matters, metric refines” calls for metric properties that provide opportunities for finer grained distinctions than the purely qualitative topological relations. This paper defines a comprehensive set of eleven metric refinements that apply to the eight coarse topological relations between two regions that the 9-intersection and the Region-Connection Calculus identify and develops the applicable value ranges for each metric refinement. It is shown that any topological relation between two regions can be derived uniquely from the conjunction of at most three such refinement specifications (i.e., pairs of metric refinements and applicable value ranges). The smallest set of refinement specifications that determine uniquely all eight relations resorts to six of the eleven metric refinements.

A Survey of Geosensor Networks: Advances in Dynamic Environmental Monitoring

Wednesday, July 15th, 2009

S. Nittel, A Survey of Geosensor Networks: Advances in Dynamic Environmental Monitoring, Sensors 2009, 9(7), 5664-5678; doi:10.3390/s90705664, published: 15 July 2009.

In the recent decade, several technology trends have influenced the field of geosciences in significant ways. The first trend is the more readily available technology of ubiquitous wireless communication networks and progress in the development of low-power, short-range radio-based communication networks, the miniaturization of computing and storage platforms as well as the development of novel microsensors and sensor materials. All three trends have changed the type of dynamic environmental phenomena that can be detected, monitored and reacted to. Another important aspect is the real-time data delivery of novel platforms today. In this paper, I will survey the field of geosensor networks, and mainly focus on the technology of small-scale geosensor networks, example applications and their feasibility and lessons learnt as well as the current research questions posed by using this technology today. Furthermore, my objective is to investigate how this technology can be embedded in the current landscape of intelligent sensor platforms in the geosciences and identify its place and purpose.

Establishing Similarity Across Multi-Granular Topological-Relation Ontologies

Monday, June 1st, 2009

Dube, M. and M. Egenhofer. Establishing Similarity Across Multi-Granular Topological-Spatial Relations. QuaCon 2009 – First International Workshop on Quality of Context, Stuttgart, Germany. D. Fritsch and K. Rothermel (eds.), Lecture Notes in Computer Science, June 2009. pp. 98-108.

Abstract. Within the Geospatial Semantic Web, selecting a different ontology for a spatial data set will enable that dataís analysis in a different context. Analyses of multiple data sets, each based on a different ontology, require appropriate bridges across the ontologies. This paper focuses on establishing such a bridge across two topological-relation ontologies of different granularity; the standard eight detailed toplogical relations and five coarse topological relations. By mapping the conceptual neighborhood graphs onto a zonal representation, the different granularities are aligned spatially, yielding a reasoned approach to determining similarity values for the bridges across the two ontologies. A comparison with bridge lengths from an averaged model shows the better quality of zonal model.

Metric Details of Topological Line-Line Relations

Friday, April 25th, 2008

Kostas Nedas, Max J. Egenhofer, and Dominik Wilmsen, Metric Details of Topological Line-Line Relations International Journal of Geographical Information Science 21 (1): 21-48, 2007.

Many real and artificial entities in geographic space, such as transportation networks and trajectories of movement, are typically modeled as lines in geographic information systems. In a similar fashion, people also perceive such objects as lines and communicate about them accordingly as evidence from research on sketching habits suggests. To facilitate new modalities like sketching that rely on the similarity among qualitative representations, oftentimes multi-resolution models are needed to allow comparisons between sketches and database scenes through successively increasing levels of detail. Within such a setting, topology alone is sufficient only for a coarse estimate of the spatial similarity between two scenes, whereas metric refinements may help extract finer details about the relative positioning and geometry between the objects. The 9-intersection is a topological model that distinguishes 33 relations between two lines based on the content invariant (empty-nonempty intersections) among boundaries, interiors, and exteriors of the lines. This paper extends the 9-intersection model by capturing metric details for line-line relations through splitting ratiosand closeness measures. Splitting ratios, which apply to the 9-intersection’s non-empty values, are normalized values of lengths and areas of intersections. Closeness measures, which apply to the 9-intersection’s empty values, are normalized distances between disjoint object parts. Both groups of measures are integrated into compact representations of topological relations, thereby addressing topological and metric properties of arbitrarily complex line-line relations.

Spatial Reasoning with a Hole

Friday, April 25th, 2008

Max J. Egenhofer and Maria Vasardani, Spatial Reasoning with a Hole, in: S. Winter, M. Duckham, L. Kulik, and B. Kuipers (eds.), Conference on Spatial Information Theory (COSIT ’07), Melbourne, Australia, Lecture Notes in Computer Science, Vol. 4736, Springer, pp. 303-320, September 2007.

Cavities in spatial phenomena require geometric representations of regions with holes. Existing models for reasoning over topological relations either exclude such specialized regions (9-intersection) or treat them indistinguishably from regions without holes (RCC-8). This paper highlights that inferences over a region with a hole need to be made separately from, and in addition to, the inferences over regions without holes. First the set of 23 topological relations between a region and a region with a hole is derived systematically. Then these relations’ compositions over the region with the hole are calculated so that the inferences can be compared with the compositions of the topological relations over regions without holes. For 266 out of the 529 compositions the results over the region with the hole were more detailed than the corresponding results over regions without holes, with 95 of these refined cases providing even a unique result. In 27 cases, this refinement up to uniqueness compares with a completely undetermined inference for the relations over regions without holes.

Perceptual Sketch Interpretation

Friday, April 25th, 2008

Markus Wuersch and Max J. Egenhofer, Perceptual Sketch Interpretation, in: A. Ruas and C.Gold (eds.), The 13th International Symposium on Spatial Data Handling (SDH 2008), Montpellier, France Springer, June 2008.

An automated extraction of regions from sketches can be of great value for multi-modal user interfaces and for interpreting spatial data. This paper develops the Perceptual Sketch Interpretationalgorithm, which employs the theory of topological relations from spatial reasoning as well as continuity and good gestalt from gestalt theory in order to model people’s perception. The Perceptual Sketch Interpretation algorithm extracts regions iteratively, removing one region at each a time, thus making the remaining sketch simpler and easier to interpret. The evaluation of the algorithm shows that the use of gestalt theory empowers the algorithm to correctly identify regions and saves processing time over other approaches.

Conceptual Neighborhoods of Topological Relations between Lines

Friday, April 25th, 2008

R. Reis, M. Egenhofer, and J. Matos, Conceptual Neighborhoods of Topological Relations between Lines, in: A. Ruas and C.Gold (eds.), The 13th International Symposium on Spatial Data Handling (SDH 2008), Montpellier, France
Springer, June 2008.

Conceptual neighborhood graphs capture the similarity among qualitative relations. This paper derives the graphs for the thirty-three topological relations between two crisp, undirected lines and for the seventy-seven topological relations between two lines with uncertain boundaries. The analysis of the graphs shows that the normalized node degree increases, from the crisp to the broad-boundary lines, roughly at the same degree as it increases for crisp lines that are transformed from R1 into R2.

Geo-Mobile Query-by-Sketch

Thursday, December 28th, 2006

David Caduff and Max J. Egenhofer, Geo-Mobile Query-by-Sketch, International Journal of Web Engineering and Technology, 3 (2): 157-175, 2007.

The advent of wireless technology, such as cellphones, PDAs, tablet PCs, and sub-notebooks, allows tranferring portions of traditional desktop-based GIS technology to mobile environments. This paper introduces Geo-Mobile Query-by-Sketch, a sketch-based spatial querying system for mobile GIS environment that combines techniques for spatial querying with mobile technologies. The system implements and adaptive client-server architecture, which copes with restrictions of mobile environments, such as fluctuating bandwidth and fre quent disconnections. The core concept analyzed is the mobile sketch, a multi-representation data structure of a sketched scene, which enables an adaption strategy that is tialored to the available transmission rates. We analyze the transmission cost of Geo-Mobile Query-by-Sketch and develop a protocol that optimizes the adaption level in order to guarantee quality of service.