- Open Access
New indoor navigation system for visually impaired people using visible light communication
© Nakajima and Haruyama; licensee Springer. 2013
- Received: 31 March 2012
- Accepted: 18 January 2013
- Published: 19 February 2013
In this study, we propose an indoor navigation system that utilizes visible light communication technology, which employs LED lights and a geomagnetic correction method, aimed at supporting visually impaired people who travel indoors. To verify the effectiveness of this system, we conducted an experiment targeting visually impaired people. Although acquiring accurate positional information and detecting directions indoors is difficult, we confirmed that using this system, accurate positional information and travel direction can be obtained utilizing visible light communication technology, which employs LED lights, and correcting the values of the geomagnetic sensor integrated in a smartphone.
- Indoor navigation
- Visible light communication
- Visually impaired people
- Location-based services
Pedestrian support for visually impaired people involves the use of textured paving blocks, guide dogs, GPS-based voice navigation systems, among others. On the other hand, studies aimed at visually impaired people report that there is a need for voice information inside buildings , and that, in the future, we will need adequate indoor pedestrian support systems in large commercial facilities, such as shopping centers and underground shopping malls. However, compared to public spaces and transport facilities, no progress is being made in providing commercial facilities with textured paving blocks , and although guide dogs are effective on obstacle-free safe walkways, they cannot locate a person’s destination. Moreover, the GPS’ inability to give an accurate position indoors is equally a problem. Therefore, positioning methods using radio waves emitted from a wireless LAN access point are increasingly employed. However, this method has encountered issues with fluctuating positional accuracy due to reflected signals from the wireless LAN, obstacles, or the surrounding environment . Studies into guidance systems using tactile maps, which are effective in creating mental maps, are also underway. However, it takes time to understand a tactile map by touch, and therefore, they are difficult to use while on the move. To address these kinds of issues, our study aims to create a usable system that enables visually impaired people, especially the blind, to travel indoors unaided. A variety of data is required to travel indoors, such as the accurate current position, travel direction, distance to the destination, and information about the barriers and surroundings. This study concentrates on solving problems relating to the current position, the travel direction, and the distance. As an indoor positioning method, we focussed on visible light communication technology using the ubiquitous LED lighting. As LED lighting is often installed in pathway ceilings, accurate positional information can be sent naturally from above the user’s head. Further, we used the geomagnetic sensor in the already widespread smartphone for a method to survey the travel direction. However, because of situations where geomagnetic sensors cannot detect the accurate direction due to the effect of, for example , rebars, and because it has been reported that they are not adequate to maintain the correct direction when walking long distances [5–7], we worked on simply improving the directional accuracy by obtaining and correcting the geomagnetic information beneath the LED lights in advance.
This article is structured as follows. In section 2, we present the necessary components of an indoor navigation system, namely, visible light communication technology and indoor map data, and then, we will discuss in detail the correction method for the pedestrian’s position and direction detection. In section 3, we present the design and implementation method of the indoor navigation system, and in section 4, we present the test results for this indoor navigation system. Section 5 discusses this system, and section 6 presents the conclusions and future research.
In this section, we describe the positioning method and the method for creating indoor map data through visible light communication, components of our ‘indoor navigation system’ and the direction detection method through geomagnetism.
2.1 Positioning for visible light communication
Indoor positioning system
Visible light communication
several meters to several hundred meters
dependence of noise, interference
dependence of noise, interference
less than a second
less than a second
Recognition of building floors
visible light receiver
Specification of Visible light ID system
2.2 Creation of indoor map data
2.3 Compensated geomagnetic sensing
First, the geographic coordinates are obtained from the visible light ID sent from an LED light. Second, the geomagnetism beneath the LED light is obtained from the geomagnetic sensors. Geomagnetic sensors show the absolute orientation by detecting the direction of the earth’s magnetic field lines, but as mentioned previously, we know that the magnetic field can be distorted in indoor spaces with rebars, etc. Therefore, we obtain the geomagnetic data beneath the LED light in advance and make corrections using these values. Third, we obtain the next LED lights’ geographic coordinates from the route to the destination and calculate the angle of the travel direction and the distance.
In this section, we present the verification test and document the verification log analysis results and the interviews with the test subjects.
4.1 The verification test
ATC Ageless Center, OSAKA
age range 50–60
age range 60–70
age range 60–70
age range 60–70
age range 50–60
age range 60-70
Experience and interview
Front - toilet (about 5min)
Visible light communication ID transfer(LED light), receiver all-in-one smartphone (P-07C/Panasonic), Headphone(SENNHEISER)
We conducted the test for one person at a time, with the users walking on their own from operation to destination. We first explained and then executed the procedure using the indoor navigation system, until the destination was reached.
While the subject was travelling, the sequence shown in Figure 3 was followed, based on the visible light ID and the geomagnetic values obtained from beneath the LED lights, and the subject was informed of the travel direction and distance. If the subject strayed from the route while travelling, the route was recalculated and the subject was re-informed.
4.2 Result of verification test
Test results showed that three people with low vision reached the goal. Three blind people arrived at the goal by checking the position of the wall along the route with their cane a few times.
After the test, we conducted interviews with all subjects.
Result of interview
Suggestion of navigation function (position, direction, distance)
It is difficult to decide the superiority or inferiority of guidance by the clock position and eight directions.
The distance to the destination was found well.
It should show the direction of movement always more correctly. The guidance should synchronize with the walking speed.
It should support, when a direction of movement changes quickly (ex; the obstacle, bump to a person).
I would like to always check whether it is walking correctly to a course.
I was not able to memorize guidance to the destination, however I have imagined it.
In this section, we will discuss the indoor navigation system, particularly the positional information and the travel direction functions. We will also discuss the results of the interviews after the test.
5.1 The positional information and the travel direction
In addition, although this was not an issue with this experiment, there is the possibility of situations occurring where the magnetic field changes and the correction does not function because of floor alterations or the presence of magnetic materials in the actual space. To solve this problem, geomagnetic values need to be obtained on these occasions, which is a hurdle in actually applying the system practically.
5.2 The results of the interviews
Because an error in the direction equivalent to a one-hour difference in the clock position is a big problem for visually impaired people and especially the blind, we concluded that a higher directional accuracy is needed. In addition, because there is an individual variation in the guidance methods for the travel direction, a significant improvement could be made by employing a configuration that allowed the user to choose, apart from clock positions, modes for guidance using, for example, eight directions or angles.
On the other hand, as some visually impaired people walk fast, the timing of the spoken navigation needs to be matched as closely as possible to the travelling speed. We need to consider a configuration where guidance is given not at a bend, but approximately 1–4m before the bend. Moreover, a feedback sound is played when an LED light is correctly passed, but, because blind people usually feel uneasy about whether they are walking a route accurately, we also want to consider a configuration that provides a continuous feedback sound while travelling.
We developed and tested an indoor navigation system for visually impaired people using visible light communication that makes use of LED lights and a geomagnetic sensor integrated in a universally used smartphone. To support travel for visually impaired people, accurate guidance for the positional information and travel direction are needed, and we have confirmed that the positional and directional accuracy improves through visible light communication and geomagnetic value correction. Therefore, we have concluded that our approach will be effectual system for the visually impaired people. An issue to consider in the future is the need to establish an azimuth accuracy detection method.
The authors would like to thank Osaka Urban Industry Promotion Center, Panasonic Corporation and Osaka Municipal Association for the Welfare of the Visually Impaired.
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