# An Outdoor Navigation System for Blind Pedestrians Using GPS and Tactile-Foot Feedback
## 2 Related Work  
The idea of exploiting GPS to assist the navigation of blind pedestrians was first introduced in the mid-1980s by [PERSON] [21] and [PERSON] [22]. In these works, conceptual designs of navigation assistive systems based on GPS were independently proposed. In particular, the latter work established the functional modules of such systems (see Figure 1): a GPS receiver that calculates the traveler's position (longitude/latitude/altitude); a geographic information system (GIS) comprised of the system software that captures, stores, manipulates, and analyzes the GPS coordinates; and the interface for presenting the information to the user. [PERSON] conducted the first experimental evaluation of GPS for assisting localization of blind pedestrians [23]. Guidance was provided via verbal instructions. However, poor positioning due to nascent GPS technology inhibited any practical application. Commercial products exploiting GPS and verbal instructions through speech synthesizers also appeared upon the development of GPS. The Strider (1994), the Atlas (1995), the GPS-talk (2000), and the BrailleNote (2001), all Sendero Group products, included in their GISs detailed digital maps of United States (US) cities with streets and points of interests and provided verbal instructions for traveling to desired destinations [24]. Improvement upon Sendero GPS technology has continued over the past decade. The most recent product, the Seeing Eye GPS, is a GPS/GIS application for mobile phones. A similar product from HumanWare Group is the Trekker Breeze [25], a handheld talking GPS/GIS, which includes information on street names, landmarks, points of interest, and public services around the pedestrian's location. Endeavors to make cities more accessible to blind pedestrians have also explored GPS and speech interfaces. The e-Adept project aims to implement in the city of Stockholm a digital network with information on paths, sidewalks, signs, stairs, and many other features to enhance the navigation of blind and disabled people [26]. In Finland, the NOPPA project uses GPS, a mobile phone, and an information server to provide door-to-door guidance for both blind and sighted users taking public transportation [27]. Figure 1: Functional modules of a global positioning system (GPS)-based navigation assistive system. Navigation guidance using verbal instructions has been studied in several research projects [28; 29; 30; 31; 32], exploring different hardware architectures and GIS approaches. Most of these systems have been validated from a strictly technical point of view. Tactile feedback has also been examined to assist the navigation and wayfinding of blind people. [PERSON] presented in [33] a prototype of tactile gloves to augment \"the white cane and guide dog\" approach to assist the navigation of blind pedestrians. [PERSON] introduced in [34] the PocketNavigator, an Android application for smartphones that uses vibrotactile feedback to provide pedestrian navigational information. Similarly, [PERSON] designed an Android-based application that uses web-service routing algorithms to provide navigational information through the vibrations of the smartphone [35]. [PERSON]'s Tactile Wayfinder consists of a torso belt display that provides directions through vibrotactile feedback [36]. [PERSON] introduced in [37] a device consisting of a pair of actuators that stimulate the ankle with vibrations encoding directions provided by a smartphone. [PERSON] compared [38] GPS navigation with two haptic modalities: vibrotactile and shape-changing with two novel interfaces, the Cricket and Animotus. Both modalities successfully guided test users to the target destination. However, information displayed by the shape-changing interface proved to be faster to understand. [PERSON] investigated in [39] vibrotactile feedback at five different body locations by reconstructing tactile display designs available in the literature, such as a sock bandage, a wristband, a belt, a foot-sole matrix display, and a side wall shoe.