No abstract

Sighted guidance is arguably the most efficient method for aiding visually impaired pedestrians in mobility. A sighted guide's verbal instructions compensate comprehensively for the insufficiency of visual input in navigation. Moreover, the companionship entails sharing of responsibilities and thus increases the blind traveller's sense of security during a journey. The disadvantages of the sighted guidance are that a sighted guide may not always be available or their presence may not be desirable because it restricts personal independence. This paper presents a novel system for navigation of visually impaired pedestrians, whereby advanced technologies were combined to allow a visually impaired user to remotely access the sighted guidance service. The user can choose when and for how long to use the system. The remote sighted guidance system is enabled by the integration of a remote vision facility with the Global Positioning System, the Geographic Information System and the third generation telecommunication network. A user trial is also reported in which the contribution of the system to the mobility of a visually impaired pedestrian was assessed. The results obtained lead to the conclusion that the remote sighted guidance is potentially a highly usable mobility aid.

This paper presents a method for correcting dead reckoning parameters, which are heading and step size, for a pedestrian navigation system. In this method, the compass bias error and the step size error can be estimated during the period that the Global Positioning System (GPS) signal is available. The errors are used for correcting those parameters to improve the accuracy of position determination using only the dead reckoning system (DR) when the GPS signal is not available. The results show that the parameters can be estimated with reasonable accuracy. Moreover, the method also helps increase the positioning accuracy when the GPS signal is available.

111 this paper we present develapmei~t of the GPS based navigation uid,/ur blind. That aid utilizes inverse DGPS positioning module which, along wit11 other hen& for the blind user, enables implementati~m o/mure cutnplu navigation algorithms. In particular, we have implemented DGPS algorithm angmented by altiiude data available from digital map. This solution improved the availabilin/ ofpositioning by more that 23% and its accuracy by more than IS%. AI1 the results were e.rperinientally verified.

This paper reports the development of a DGPS navigation system integrated with altitude aiding. In this system, a digital height dataset is used for altitude augmentation. A twodimensional (2-D) positioning algorithm is discussed and modified based on previous publications. The developed algorithm was implemented on the Brunel Inverse DGPS system. The performance of the new developed system is experimentally verified and compared with three-dimensional (3-D) GPS and DGPS systems. The experimental results showed 86 % availability of positioning services ; whereas for the 3-D GPS system alone, the availability was only 63 % of time. In addition, the accuracy of the system was improved from 7n1 to 6n1 m (RMS) for GPS and from 6n0 to 5n1 m (RMS) for DGPS when compared to standalone 3-D modes.KEY WORDS 1. GPS.2. Land Navigation. 3. Augmentation.1. INTRODUCTION. In urban canyon areas, the availability and accuracy of GPS-based systems can be degraded due to blocking of the satellite signals. If another sensor can provide altitude information, two-dimensional (2-D) GPS positioning can be a remedy for some applications, providing an improvement in system performance. During normal GPS receiver operations, pseudo-ranges from four GPS satellites are needed to solve the equations for the receiver's antenna position because of the four unknowns : three position unknowns and the receiver's clock bias (x, y, z, ∆t). When less than four satellites are available, or the current geometry of satellites is poor, a GPS receiver (system) can operate in an augmented mode using additional positioning information from an external sensor. The concept of 2-D positioning systems is well known (DoD, 1996 ;Parkinson and Spilker, 1996 ;Brown and Struza, 1993 ; McBurnley and Braisted, 2000). The more detailed descriptions have been patented in several applications using different sensors for altitude augmentation. Nevertheless, most of these systems have only been described theoretically without creating a real working system that could be tested in order to assess its performance and usability. This paper presents and discusses a 2-D positioning algorithm to which changes are proposed. This proposed algorithm, using a digital height dataset for altitude augmentation, has been implemented on the Brunel University 2-D inverse DGPS positioning system. The performance of the newly developed system is experimentally verified and compared with 3-D GPS and DGPS systems.