1. Are indoor positioning systems mature
for cartographic tasks?
Evaluating the performance of a commercial
indoor positioning system
Terje Midtbø
Norwegian University of Science and Technology

2. View of the world?

3. When we move indoor....

4. Overview
• Indoor maps
• Indoor navigation
• Testing the WiFi positioning system at NTNU
• Measurements
• Results
• Discussions and conclusions

5. Do we need indoor navigation?
• Localization of persons and equipment at
for example hospitals
• Find your way in large complex and
unknown buildings
• Find products in large shopping areas
• Most efficient shopping based on shopping
list
• Tourists at a museum
• Alternative emergency exits
• Localization of firefighter
• …….

6. Indoor maps

7. Indoor visualization

8. Indoor maps

9. Floor plans

10. Map made by Jaan Tarmak

12. Floor plans

13. Indoor tube

15. Indoor navigation

16. GPS-”repeaters”

17. RFID-system
- Present?

18. Systems based on ultrasound
- Need free line of sight

19. Infrared signals
- Present?

20. Bluetooth

21. Location by phone signals

22. WiFi positioning systems

23. WiFi positioning systems
• Time for signal one way
• Time for signal both ways
• Time for signal in combination with angle
to the access points
• Phase measurements
• Signal strength

24. Indoor navigation

25. Cisco positioning system at Norwegian
University of Science and Technology (NTNU)

26. Investigation of the Ciscosystem at NTNU

27. Network of control points

28. Measurements
• Accurate measurement of control points by
surveying equipment and methods
• New measured coordinates for the access
points
• Coordinates measured in UTM, Zone 32N
• Transformed into local system used by the
Cisco system. Units in feet.

29. New coordinates for the access points
• Average 2D differences: 11.7 feet
• Min: 3.7 feet
• Max: 19.2 feet

30. Measurement of positions
by using WiFi

31. Measurement application
• Web-based interface
• Measured data stored in SQLite database
• Both UTM and local coordinate systems

32. Equipment for the measurement
• Laptop with external antenna
• Fixed height over the floor
• Easy to move to next position

33. Measurements based on 4 configurations
• Old coordinates for access points – no
fingerprinting
• Old coordinates for access points with
fingerprinting
• New coordinates for access points – no
fingerprinting
• New coordinates for access points with
fingerprinting

34. Measurements based on 4 configurations
• 10 points were measured in the 1st floor of
Lerkendalsbygget
• 5 measurements for each point in each
configuration

35. Results

36. Differences from
true values

37. Measured point and access points

38. Correlation coefficients
X-components, 1- 4
Y-components, 1- 4

39. Variances

40. Differences from
true values

41. Discussion and
conclusions

42. • More accurate coordinates for access points gave no
significant improvement for measured position
• Fingerprinting as it is used today shows no significant
improvement in the measured position. Lower variance
is still observed.
• Correlation between different types of measurements in
the same control points indicate that geometry and
obstacles are the dominating sources of error
• Further research: include obstacles in the model

44. • More accurate coordinates for access points gave no
significant improvement for measured position
• Fingerprinting as it is used today shows no significant
improvement in the measured position. Lower variance
is still observed.
• Correlation between different types of measurements in
the same control points indicate that geometry and
obstacles are the dominating sources of error
• Further research: include obstacles in the model
• Still too poor precision and accuracy for turn-by-turn
navigation
• Acceptable for localize equipment
• Acceptable for overview of peoples position in social
applications