Portable and Mobile Systems in Assistive Technology - GPS and Inertial Measurement Unit (IMU) as a Navigation System for the Visually Impaired - Zegarra, Jesus (s)

1. GPS AND INERTIAL
MEASUREMENT UNIT AS
A NAVIGATION SYSTEM ICCHP 2012
FOR THE VISUALLY
IMPAIRED
Author s:
Jesus ZEGARRA
René FARCY
Laborator y Aimé
Cotton ( France)

2. OBJECTIVES
-To develop a device which can give to the visually
impaired the possibility to navigate to new places
in the cities; as a consequence, give a better
quality of life.
- To provide the instantaneous direction of the
blind person even if stopped
-To compensate GPS echoes and magnetic field
perturbations in urban areas
- Show the advantages and limitations of the whole
system relatively to standard GPS devices.

3. PROBLEMS
 GPS signal deficiencies (SIRF 3 - last generation): do
not give a right heading when they are in the cities
(hard reception conditions).
Real way
urban environment Antenne GPS SIRF 3
GPS Smart Phone
Samsung OMNIA
GPS SIRF 3

4. PROBLEMS
 The GPS devices do not give the right heading
when the user does not move (It is necessary a
minimum of speed for updating the heading)
 15 Km/h in average for having a right heading
 Basic solution : the use of one IMU for giving the
right heading in magnetic field perturbation
conditions.
 Objective: To update a correct heading every
second for a speed less than 15km/h.

5. HOW TO GIVE THE VOCAL INFORMATION
TO THE NEXT POINT?
 The unit system is :
 - meters for the distances
 - time dial for the directions i.e. : from 1 o’clock to 12 o’clock
with one hour of precision
 for instance, “12 o’clock, 40 meters” means go straight, 40
meters, “9 o’clock, 90 meters” means turning left and walk 90
meters

6. INFORMATION TO THE NEXT POINT
For improving the information
-We have done extra information about the next point « Way to»:
-For instance:
<<Way to 2 hours>>, means that the next point n+ 1 turn to the
right taking into consideration the orientation of the person
-
-

7. SOLUTION
 Use of an IMU (Inertial Measurement Unit),
developed in the laboratory containing : a 3 axis
accelerometer, a 1 axis gyroscope, a 3 axis compass
and a module Bluetooth transmitter to merge
information with the GPS. The device is placed on
the right side of the person.
GPS IMU

8. MAIN DESIGN
Module
3 axis Bluetooth
compass Filter
sensor Rx-
Tx Bluetooth Internet
1 axis Smart
Filter
gyroscope dsPic Phone
3 axis
accelerometer Filter GPS
sensor

9. HOW TO USE THE DEVICE?
 There are three ways of saving the GPS coordinates
(latitude and longitude) of the destination point.
 Saving using the GPS antenna –used in the
Navigation Window
 Saving the coordinates by writing
the adress of the destination
 Saving the coordinates by writing
directly the coordinates GPS
Keyboard 12 bottons
Window

10. NAVIGATION WINDOW-BRAILLE SYSTEM
Chosing the point Boutton for saving
of destination the current
coordinates GPS
Close the
Navigation
window
The user can chose the
points around him
between 2km, 5 km
and all the points
closer to him
Heading and
Information about
distance to the
the current adress
point of
destination

11. TEST TECHNIQUE (IMPROVEMENT OF
HEADING)
Heading
(°) Heading (°)
Heading
POIINTS Cartograp GPS 3,6
(IMU)
hique km/h
P1 291 280 330
P2 56 65 43
P3 109 110 100
P4 21 25 0
P5 50 55 25
P6 27 30 55
P7 32 30 25
P8 108 100 140
Average Error 5,375° 21,75°
Max Error 11° 39°

12. TESTS ABOUT THE USE OF THE WHOLE
SYSTEM
-The tests were conducted in Paris in the
thirteenth, fourteenth and tenth neighborhood
in bad GPS reception conditions : high buildings
in small streets and bad magnetic conditions :
walking along the Senna river (electrical
cables), crossing metallic bridges, etc.
-Six points of destination were chosen (the
distance between the destination can vary from
3 to 5 km). Ten visually impaired people tested
the system (in category 3, 4 and 5 according to
the World Heath Organization) .
-

13. RESULTS
 All the subjects arrived to the destination points
alone (except one who was not confident enough
after training to make the tests).
 The benefits about the use of GPS seem to be
proportional to the initial autonomy of the visually
impaired.
 Teaching the way of using the device is faster for the
subjects in category 3 than for those in category 4
and 5.
 The main problem is keeping the security for the user
that suddenly increased his autonomy in unknown
environments. The risk was the same for the three
categories.

14. CONCLUSIONS
 The GPS system coupled to IMU is better because the
heading is more stable in the pedestrian navigation
and, the person does not have to walk for knowing the
direction to go.
 The information about heading and distance is important
because it lends us to arrive to the final destination with
only the coordinates GPS of the final destination . It also
works even when the cartography of the place is not well
elaborated because the person can take any direction
and the system can guide him until the destination . It
seems to be one reliable guiding system option for the
blind people in the cities .
 Good autonomy of the whole system (6 hours enough
for arriving one destination of 7 km)

15. THANK YOU FOR YOUR
ATTENTION