The increase in the life expectancy has led to a higher number of elderly people accessing technology and mobile devices (cell phones and tablets). However, in general, the elderly present difficulties in this interaction because, in addition to the physical limitations imposed by aging, many applications were not properly designed to consider such restrictions. This paper presents the results of a survey pointing out main difficulties that elderly people face when using mobile devices and proposes strategies to overcome these barriers. The research was carried out by applying questionnaires in the form of customized applications. Based on the answers, some alternatives were proposed to try to circumvent the reported difficulties and to make the elderly acquire autonomy and use their devices safely, efficiently, without frustration regardless of their physical limitations. In order to evaluate and validate the proposals, a framework was developed to make it easier for application developers to create interfaces that incorporate the proposed strategies.

We present an algorithm to compute the intersection of two 3D triangulated meshes. It has applications in GIS, CAD and Additive Manufacturing, and was developed to process big datasets quickly and correctly. The speed comes from simple regular data structures that parallelize very well. The correctness comes from using multiple-precision rational arithmetic to prevent roundoff errors and the resulting topological inconsistencies, and symbolic perturbation (simulation of simplicity) to handle special cases (geometric degeneracies). To simplify the symbolic perturbation, the algorithm employs only orientation predicates. This paper focuses on the challenges and solutions of the implementing symbolic perturbation. Our preliminary implementation has intersected two objects totalling 8M triangles in 11 elapsed seconds on a dual 8-core Xeon. The competing LibiGL took 248 seconds and CGAL took 2726 seconds. Our software is freely available for nonprofit research.

We present Grid-Gen, an efficient heuristic for map simplification. Grid-Gen deals with a variation of the generalization problem where the idea is to simplify the polylines of a map without changing the topological relationships between these polylines or between the lines and control points. Grid-Gen uses a uniform grid to accelerate the simplification process and can handle a map with more than 3 million polyline points and 10 million control points in 9 seconds in a Lenovo T430s laptop.

We present a better algorithm and implementation for external memory viewshed computation. It is about four times faster than the most recent and most efficient published methods. Ours is also much simpler. Since processing large datasets can take hours, this improvement is significant. To reduce the total number of I/O operations, our method is based on subdividing the terrain into blocks which are stored in a special data structure managed as a cache memory.

In this paper, we present the main results of the BioSecure Signature Evaluation Campaign (ESRA'2011). The objective of ESRA'2011 is to evaluate through two different tasks the resistance of different online signature systems to skilled forgeries categorized automatically according to their quality. Task 1 aims at studying with only coordinate time functions the influence of acquisition conditions (digitizing tablet vs. PDA) on systems' performance. The two BioSecure Data Sets DS2 and DS3 make this possible, since they contain data from the same 382 people, acquired respectively on a digitizer and on a PDA. Task 2 then aims at assessing the contribution of the five time functions available on a digitizer (coordinates, pressure, pen inclination) on systems' resistance to different qualities of skilled forgeries. Results of the 13 systems involved in this competition are reported and analyzed for both tasks in this paper. We observe that the best system in terms of performance on forgeries of "bad" quality is not necessarily the most resistant to an increased quality of skilled forgeries. Also, we note that mobile conditions are still threatening independently of the quality of forgeries. Finally, when adding pen inclination time functions to pressure and coordinates, we find that the gap between systems in terms of performance is wider than when only pen coordinates and pressure are considered.

This paper presents an heuristic method to give an approximated solution to the observer siting problem on high resolution terrains that are too large to be processed in the internal memory. Informally, the problem is to determine an optimal positioning of as few as possible observers for being able to observe as many target points as possible. Tests have shown that the proposed heuristic can solve this problem using, on average, fifteen percent fewer observers than another heuristic described in the literature. This will permit more efficient positioning of facilities such as mobile phone towers, fire observation towers, and vigilance systems.

We introduce a parallel approximation of an Over-determined Laplacian Partial Differential Equation solver (ODETLAP) applied to the compression and restoration of terrain data used for Geographical Information Systems (GIS). ODETLAP can be used to reconstruct a compressed elevation map, or to generate a dense regular grid from airborne Light Detection and Ranging (LIDAR) point cloud data. With previous methods, the time to execute ODETLAP does not scale well with the size of the input elevation map, resulting in running times that are prohibitively long for large data sets. Our algorithm divides the data set into patches, runs ODETLAP on each patch, and then merges the patches together. This method gives two distinct speed improvements. First, we provide scalability by reducing the complexity such that the execution time grows almost linearly with the size of the input, even when run on a single processor. Second, we are able to calculate ODETLAP on the patches concurrently in a parallel or distributed environment. Our new patch-based implementation takes 2 seconds to run ODETLAP on an 800 x 800 elevation map using 128 processors, while the original version of ODETLAP takes nearly 10 minutes on a single processor (271 times longer). We demonstrate the effectiveness of the new algorithm by running it on data sets as large as 16000 x 16000 on a cluster of computers. We also discuss our preliminary results from running on an IBM Blue Gene/L system with 32,768 processors.

We present a better algorithm for path planning on complex terrain in the presence of observers and define several metrics related to path planning to evaluate the quality of various terrain compression strategies.

We present the GeoStar project at RPI, which researches various terrain (i.e., elevation) representations and operations thereon. This work is motivated by the large amounts of hi-res data now available. The purpose of each representation is to lossily compress terrain while maintaining important properties. Our ODETLAP representation generalizes a Laplacian partial differential equation by using two inconsistent equations for each known point in the grid, as well as one equation for each unknown point. The surface is reconstructed from a carefully-chosen small set of known points. Our second representation segments the terrain into a set of regions, each of which is simply described. Our third representation has the most long term potential: scooping, which forms the terrain by emulating surface water erosion.Siting hundreds of observers, such as border guards, so that their viewsheds jointly cover the maximum terrain is our first operation. This process allows both observer and target to be above the local terrain, and the observer to have a finite radius of interest. Planning a path so that a smuggler may get from point A to point B while maximally avoiding the border guards is our second operation. The path metric includes path length, distance traveled uphill, and amount of time visible to a guard.The quality of our representations is determined, not only by their RMS elevation error, but by how accurately they support these operations.

We develop exact algorithms for geometric operations on general circles and circular arcs on the sphere, using integer homogeneous coordinates. The algorithms include testing a point against a circle, computing the intersection of two circles, and ordering three arcs out of the same point. These operations allow robust manipulation of maps on the sphere, providing a reliable framework for GIS, robotics, and other geometric applications.