Evaluation of an Orientation and Navigation Aid
for Visually Impaired Travellers
Thomas Strothotte
Department of Simulation and Graphics,
Otto-von-Guericke University of Magdeburg
Universitätsplatz 2, D-39106 Magdeburg
tel: +49 391 671 8772,
fax: +49 391 671 1164,
email: tstr@isg.cs.uni-magdeburg.de
Valerie Johnson and Helen Petrie
Sensory Disabilities Research Unit
University of Hertfordshire
Hertfordshire AL10 9AB, UK
tel: +44 1707 285 058
fax: +44 1707 285 059
email: h.l.petrie@hertfordshire.ac.uk
Graeme Douglas
Research Centre for the Education of the Visually Handicapped
University of Birmingham
Edgebaston, Birmingham B15 2TT
tel: +44 121 414 6733
fax: +44 121 414 4865
email: g.d.a.douglas@bham.ac.uk
1 Summary
An interactive system to aid blind and elderly people in navigation and mobility in unknown urban environments whilst moving about as pedestrians has been developed. Its emphasis is on providing users with information as to their surroundings and the route to be taken. In this paper we report on the primary technical features of the final prototype and the experience gathered during an extensive field trial.
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2 Introduction
The MoBIC project (Mobility of Blind and Elderly People Interacting with Computers) was carried out under the TIDE programme from 1994 to 1977. Its primary objective has been to increase the independent mobility of blind and elderly people in unfamiliar urban environments. Based on intensive user needs studies, an interactive system was developed. The system is aimed at providing with information about the medium range, like where certains shops, road intersections and hasards are, and where the user currently is with respect to such landmarks. Thus it supports the primary aid without trying to replace it, while giving the user more confidence when moving about.
The MoBIC system is composed of two parts:
- The MoBIC prejourney system (MoPS) to enable a blind person to get information about the environment in preparation of a journey and to assist the user in route planning. This system can be used by blind/elderly people to explore an area before going outside. Using the cursor keys, the user can control a virtual pedestrian. In this simulated journey, the pedestrian can get all the information as though he or she were really outside. The information about the environment is given to users in an acoustic form. In addition, tactile maps have also been investigated for the journey preparation.
- The MoBIC outdoor system (MoODS) based on the global positioning system GPS for giuding users en route. It consistens of a 486 computer the size of a credit card (using the PC-104 industrial standard for the PC kernel and the PCMCIA standard), a compass, a GPS/DGPS receiver, and a mobile phone (GSM); input is given via a small keypad, while output is obtained with special earphones. The hardware already weights less than 5 kilograms (most of it for the batteries). Using the sateline signal, the sysem determines the accurate position of the traveller and presents it in an understandable way upon request. It provides the user with access to information pertaining to the current surroundings, as well as the next leg of the route to be taken by the blind/elderly pedestrian.
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3 A Conceptual View of MoBIC
Blind people have two types of problems in moving through the environment, particularly if it is unfamiliar. The first type of problem is that they need to avoid obstacles and to find a clear path to walk in their immediate environment. We refer to this task as micro-navigation. The second type of problem is that blind people need to orient and navigate through the larger environment, which may require knowing what street they are on, which way they are facing, where to cross a street safely and so on (macro-navigation). Without visual information, macro-navigation can be enormously difficult and the MoBIC system was developed in response to this particular problem.
Fully functioning prototypes of the MoBIC system were evaluated in a six month field trial held in Birmingham, UK. Participants were trained in the use of the system and used it in their everyday lives. Thirteen blind people took part, twelve using MoBIC for three months and one for six months. Case histories were compiled for each participant based on weekly training sessions and case study meetings of the research team. Semi-structured exit interviews were conducted with each participant and two focus groups were held. In addition, Intensive Evaluation Sessions allowed for controlled testing of both components of the MoBIC system. In this paper, we will emphasize only the intensive evaluation sessions; the interested reader is referred to the final project report for more details of the results (Strothotte, 1997).
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4 Results of the Intensive Evaluation Sessions
Intensive evaluation sessions were conducted with seven people who were taking part in the field trials and who had received training in the use of the MoBIC. Participants studied two unfamiliar routes using MoPS and then, when they felt confident, went out and walked these routes. In one condition, they used both MoODS and their primary aid, in the other condition only the primary aid was used. A battery of measures was used for evaluation including measures of performance, workload and stress.
No significant differences were found on measures of either performance or stress, but the NASA Task Load Index (TLX) revealed differences in the mental demand involved. The TLX measures overall workload and what are considered to be its six components: mental demand, physical demand, temporal demand, own performance, effort and frustration. There was no significant difference between perceived workload overall when walking with and without MoODS. However, when each component of workload was analysed individually, a significant increase was found in mental demand when travelling without MoODS (F1,6 = 5.81 P< 0.05, repeated measures analysis of variance). This effect is illustrated in Figure 1 below.
Figure 1: Perceived mental demand with and without MoODS
Usability, learnabilty and acceptability of the MoBIC system were investigated through the use of rating scales and open-ended questions. As shown in Figures 2 and 3, ratings given for both components was quite high and in all cases above the mid-point on the 7 point scale. The questions used were as shown below, with questions 4 and 5 being relevant only to the outdoor system.
1. Overall how easy did you find it to operate this system?
1 = Very difficult to 7 = Not at all difficult
2. How easy was it to learn to use this system?
1 = Very difficult to 7 = Not at all difficult
3. How efficient did you think the system was for giving information?
1 = Not at all efficient to 7 =Very efficient
4. How effective do you think the outdoor system is for providing en route information?
1 = Not at all effective to 7 =Very effective
5. Did you feel at all conspicuous using this system?
1 = Very conspicuous to 7 = Not at all conspicuous
6. How satisfied are you with this system as an aid to navigation?
1 = Not at all satisfied to 7 =Very satisfied
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5 Conclusion
The results of the field trial showed that visually impaired people, with appropriate training, can successfully use the MoBIC system to plan and navigate journeys. Participants were generally very positive and excited about the MoBIC system and the potential that such an aid has for them. Both MoPS and MoODS components were positively received by participants and both received high ratings for usability and learnability. Commercialisation of the system is currently underway.
Figure 2: Ratings of usability, learnabilility and satisfaction for MoODS
Figure 3: Ratings of usability, learnabilility and satisfaction for MoPS
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Literature:
Strothotte T. (Ed.) (1997), Mobility of Blind and Elderly People Interacting with Computers, Final Report of the TIDE Project, available from the editor (see address on the first page of this paper).
Petrie H, Johnson V, Strothotte T, Raab A, Fritz S, Michel R. (1996), MoBIC: Designing a travel aid for blind and elderly people, Journal of Navigation 49(1), 45-52.
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