Percorrer por autor "Filipe, Vitor"
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- Correction to: A review of assistive spatial orientation and navigation technologies for the visually impairedPublication . Fernandes, Hugo; Costa, Paulo; Filipe, Vitor; Paredes, Hugo; Barroso, JoãoThe fourth author name was missed in the original publication. The correct list of authors should read as “Hugo Fernandes, Paulo Costa, Vitor Filipe, Hugo Paredes, João Barroso”. It has been corrected in this erratum. The original article has been updated.
- Fuzziness measure approach to automatic histogram thresholdPublication . Lopes, Nuno Vieira; Bustince, Humberto; Filipe, Vitor; Melo-Pinto, PedroIn this paper, an automatic histogram threshold approach based on a fuzziness measure is presented. This work is an improvement of an existing method. Using fuzzy logic concepts, the problems to find a minima of a criterion function are avoided. Similarity between gray levels is the key to find an optimal threshold. Two initial regions of gray levels, located at the boundaries of the histogram, are defined. Then, using an index of fuzziness, a similarity process is started to find the threshold point. A significant contrast between objects and background is assumed. Previous histogram equalization is used in small contrast images. No prior knowledge of the image is required.
- Location based Services for the Blind Supported by RFID TechnologyPublication . Fernandes, H.; Filipe, Vitor; Costa, Paulo; Barroso, JoãoNowadays, navigation systems are widely used to find the correct path, or the quickest, between two places. These systems use the Global Positioning System (GPS) and only work well in outdoor environment since GPS signals cannot easily penetrate and/or are greatly degraded inside of buildings. Several technologies have been proposed to make navigation inside of buildings possible. One such technology is Radio-Frequency Identification (RFID). In the case of outside environments, some hybrid systems have been proposed that use GPS as main information source and RFID for corrections and location error minimization. In this article we propose a navigation system that uses RFID as the main technology to guide people with visual impairment in unfamiliar environments, both indoor and outdoor, complementing the traditional white cane and providing information about the user's geographical context.