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

View of the world?

When we move indoor....

Overview

• Indoor maps • Indoor navigation • Testing the WiFi positioning system at NTNU

• Measurements • Results

• Discussions and conclusions

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 • …….

Indoor maps

Indoor visualization

Indoor maps

Floor plans

Map made by Jaan Tarmak

Floor plans

Indoor tube

Indoor navigation

GPS-”repeaters”

RFID-system

- Present?

Systems based on ultrasound

- Need free line of sight

Infrared signals

- Present?

Bluetooth

Location by phone signals

WiFi positioning systems

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

Indoor navigation

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

Investigation of the Cisco-system at NTNU

Network of control points

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.

New coordinates for the access points

• Average 2D differences: 11.7 feet • Min: 3.7 feet • Max: 19.2 feet

Measurement of positions by using WiFi

Measurement application

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

Equipment for the measurement

• Laptop with external antenna • Fixed height over the floor • Easy to move to next position

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

Measurements based on 4 configurations • 10 points were measured in the 1st floor of

Lerkendalsbygget • 5 measurements for each point in each

configuration

Results

Differences from true values

Measured point and access points

Correlation coefficients

X-components, 1- 4 Y-components, 1- 4

Variances

Differences from true values

Discussion and conclusions

• 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

• 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