The research on outdoor environments mainly addresses the problem

The research on outdoor environments mainly addresses the problem of users positioning during micro-navigation and macro-navigation [1]. Micro-navigation studies the delivery of information from the immediate physical environment, and macro-navigation explores the challenges of dealing with Bioactive compound the distant environment. In both cases the use of global positioning systems (GPS) has shown to be quite useful in recognizing the user’s Inhibitors,Modulators,Libraries position.The studies focused on indoor environments have proposed several ad hoc technologies and strategies to deliver useful information to the user [1]. However, just some of them are suitable Inhibitors,Modulators,Libraries to be used by visually impaired people. For example, Sonnenblick [9] implemented a navigation system for indoor environments based on the use of infrared LEDs.
Such LEDs must be strategically located in places used by the blind person to perform their activities (e.g., rooms and corridors), thus, acting as guides for them. The signal of these guiding LEDs is captured and interpreted by a special device which transforms it into useful information to support the user’s movements. The main limitation of such Inhibitors,Modulators,Libraries a solution is the use of an infrared receptor instead of a device with large coverage such as an infrared camera. Because the infrared signal must be captured to identify the user’s position, the receptor device must point directly at the light source (e.g., the LEDs), thus losing the possibility of smooth integration between the device and the environment.Hub, Diepstraten and Ertl [6] developed a system to determine the position of objects and individuals in an indoor environment.
That solution involved the use of cameras to detect objects and direction sensors to recognize the direction in which the user is moving. The main limitation of that proposal is the accessibility of the technology used to implement it, since the system requires a specialized device to enable the user to interact with the environment. This system also pre-establishes possible Inhibitors,Modulators,Libraries locations for the cameras, which also generates several limitations; for example the detection process requires the person points out his white cane at the eventual obstacles.In a later work, Hub, Hartter and Ertl [7] went beyond their previous proposal and included in the Brefeldin_A system, the capability of tracking various types of mobile objects, e.g., people and pets.
Then, using an algorithm similar to human perception, they attempted to identify such tracked objects by comparing their color and shape, with a set of known objects.Treuillet and Royer [11] proposed an interesting vision-based navigation system to guide visually impaired people in indoor and outdoor environments. The positioning system uses reference 2 a body mounted camera that periodically takes pictures from the environment, and an algorithm to match (in real-time) particular references extracted from the images, with 3D landmarks already stored in the system.

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