Chaulio Ferreira

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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(More)
This work deals with the observer siting problem in terrains represented by digital elevation matrices. This problem consists in minimize the number of observers needed to see (or cover) a given percentage of a terrain. Two heuristics are proposed to solve this problem and these heuristics are compared with a method described in literature. Tests show that(More)
This paper describes a new parallel raster terrain visibility (or viewshed) algorithm, based on the sweep-line model of [Van Kreveld 1996]. Computing the terrain visible from a given observer is required for many GIS applications, with applications ranging from radio tower siting to aesthetics. Processing the newly available higher resolution terrain data(More)
This paper presents an efficient method to determine a set of observers (that is, where to site them) such that a given percentage of a terrain is visually covered. Our method extends the method proposed in (Franklin, 2002) including a local search heuristic efficiently implemented using dynamic programming and GPU parallel programming. This local search(More)
This paper proposes an efficient parallel heuristic for siting observers on raster terrains. More specifically, the goal is to choose the smallest set of points on a terrain such that observers located in these points are able to visualize at least a given percentage of the terrain. This problem is NP-Hard and has several applications such as determining(More)
We present a patch-based approach for tsunami simulation with parallel adaptive mesh refinement on the Salomon supercomputer. The special architecture of Salomon, with two Intel Xeon CPUs (Haswell architecture) and two Intel Xeon Phi coprocessors (Knights Corner) per compute node, suggests truly heterogeneous load balancing instead of offload approaches,(More)
Viewshed (or visibility map) computation is an important component in many GIScience applications and, as nowadays there are huge volume of terrain data available at high resolutions, it is important to develop efficient algorithms to process these data. Since the main improvements on modern processors come from multi-core architectures, parallel(More)
This article presents T<scp>iled</scp>VS, a fast external algorithm and implementation for computing viewsheds. T<scp>iled</scp>VS is intended for terrains that are too large for internal memory, even more than 100,000&#215;100,000 points. It subdivides the terrain into tiles that are stored compressed on disk and then paged into memory with a custom cache(More)
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