Instrumentation & Measurement Magazine 23-4 - 10

commands to the foot-based interface via Bluetooth (Fig. 8a).
The four instructions were translated to actuator commands
as shown in Fig. 5. A fifth pattern representing 'stop' (S) was
displayed as the well-known pattern for SMS alerts in mobile
phones: two consecutive vibrations, then a pause, and again
two consecutive vibrations. Fig. 8b shows the corresponding
instrumentation.
A research assistant walked 5 to 10 m ahead of the subject
with the sole purpose of previewing/intervening in any unexpected risky situation.

Experimental Procedure
Method: Before the test, both subjects completed the navigational instruction recognition (static) test in their own homes
to get used to the interface. The results were considered satisfactory. The subjects were then transported by car from their
respective homes to the chosen environments.
Subjects were totally unaware about the locations. They
were asked to move according to the pattern felt. Subjects were
asked to use the white cane as they would do normally on a
common walk. They had no time restrictions in which to complete the test. They were aware that an assistant was nearby
and that they could terminate the test at any time if they felt
uncomfortable. For both subjects, GPS coordinates and navigation times were registered in the GIS.

Fig. 8. Wearable electronic device for assisting blind travelers: (a) Schematic
architecture of the system. The smartphone incorporates the GIS and the
route planner and sends the direction commands to the tactile display. (b) The
smartphone coupled with the foot-based third interface prototype.

impairment in tactile sensory or cognitive functions. Both are
considered expert white cane users as they reported more than
10 years of experience.
Two urban environments in the city of Aguascalientes,
Mexico were chosen for the experiment. For safety reasons,
they were carefully selected for exhibiting low vehicle traffic. Static and dynamic obstacles caused by objects and other
people were present in both locations. Starting and finishing
points representing 380-420 m distances were fixed prior to
the test.
For the experiment, a smartphone (Samsung Galaxy S5
running Android 4.4.2) was used for GPS coordinate and
orientation acquisition. Real-time GPS coordinates were locally processed in the mobile device using OpenStreetMap
[21], an open source geographic information system (GIS) devoted to locate the user in the map, and YOURS [22], an open
source route planner to compute the shortest pedestrian route
to a chosen destination. The smartphone sent instruction
10

Results: The proposed environments and the paths followed
by the blind subjects are shown in Fig. 9. Both subjects successfully completed the task with no errors.
The task in environment 1 (E-1) consisted of guiding the
subjects along a 380 m pathway from a random street point
to a church (Fig. 9a). A set of 11 directions was communicated
for this purpose. The task in environment 2 (E-2) consisted of
guiding the subjects along a 420 m pathway from a close road
to a park's corner (Fig. 9b). A set of 17 directions was communicated regarding the route. The subjects' navigation was
performed on sidewalks except when crossing streets. Typical urban obstacles, such as trees, street poles, trash bins, and
other people, were encountered and overcome using the white
cane.
Fig. 10 compares the average walking speeds of the subjects
during the test. Speeds from 1.08 to 1.19 m/s were observed.
The average walking speed of a normally sighted person is 1.4
m/s [23], which suggests that the navigation system does not
reduce walking pace.
An approximate 2-4 m resolution of the GPS longitude/
latitude data provided by the smartphone was observed during the test. During the experiments, we could observe that
subjects were initially confused by the GPS imprecisions, but
with the aid of the white cane, they quickly learned to manage the situation fairly well. A natural fearless walking could
be perceived during navigation together with firm doubtless
movements.
During a post-test interview, the subjects stated the intuitiveness of the information displayed and the low cognitive

IEEE Instrumentation & Measurement Magazine

June 2020

Instrumentation & Measurement Magazine 23-4

Table of Contents for the Digital Edition of Instrumentation & Measurement Magazine 23-4