Indoor orientation and navigation in buildings and underground public transport is still a challenge. A key problem is the determination of the levels, e.g. floors and platforms, especially in environments with large amount of balconies and more or less levitating escalators, lifts and stairs. Another desired application is navigation or at least orientation in public undergrounds, which is missing due to missing common available sensors. GPS is not available in tunnels. Wifi cells are very unusual at least in the Berlin underground environment. Infrastructure based sensors and communication would be able to solve a personal navigation, but requires investments. With the introduction of barometer as a sensor in the Android 2.3 API and the first available Android mobile phones with build-in barometer sensors (Xoom and Galaxy Nexus), pressure can be used to calculate altitudes or even more relevant to measure pressure differences, e.g. between building levels and stations. This talk is intended to give and get a feeling about the given accuracy and robustness in relation to indoor positioning for buildings and undergrounds and should report about the ongoing, but already promising experiments.

1. Indoor and underground
orientation and
navigation
by using the barometer
sensor
Elizaveta Karpakova, 3. Sem.
Geoinformation Master mit Kaatz,
Richter und Zimmermann (Geoality
GbR), … und
Prof. Dr. Roland-M. Wagner
Droidcon 2012, Berlin, Urania, 14.3.2012

2. Overview
1. Problem statement for indoor orientation & navigation
2. Application example: (Berlin) Underground
3. Approach with Barometer
4. Data-collection
5. Analysis
6. Conclusion
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3. Problem statement for indoor orientation
 Do you need an (outdoor) navigator?
 1992: no
 2012: yes
 GPS is not usable for indoor orientation and positioning, other
sensors are needed
 Challenge: Change!
 More Change in indoor environment, e.g. fairs, cons
 Some privacy aspects, e.g. indoormaps only for welcomed
visitors and not for everybody in the net; => local infrastructure
 Additional indoor information needed, e.g. pics, contact, time,
location => e-flyer
 An early project is: openfloormap.org
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4. Application example: (Berlin) Underground
 Undergrounds are used by
million people every day
 Many are tourists and need
permanent orientation &
navigation
 Orientation needed also
between stairs and stations
 Frequent users might be
interested e.g. for a wake-
up app
 Only a few underground CC-At-By Ingo http://www.flickr.com/photos/30184910@N06
operators offer an (open)
interface
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5. Approach with Barometer
 Cell-id Positioning in Undergrounds allows to define the line
and a position between 4-6 stations
 Underground stations have different altitudes due to crossings
and surface
 Barometer / pressure measurement is robust and does not
require much energy
 Moving train
pressure change
for station counting
 Only deltas are
needed
 Absolute altitude
calculation with
weather service
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6. Data-collection
Specialized app to
capture the
context
Which line?
Which direction
Walking / Stairs
Train movement
Capturing of all
smartphone
available sensor
data
https://play.google.com/store/apps/details?id=de.geoality.activitys
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7. Analysis: Characteristics I
 Multiple underground train stations with filter
Sensor Pressure
Filtered Pressure
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8. Analysis: Characteristics II
Underground Station
Pressure changes
due to tunnel effects
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9. Conclusion
 Cellid positioning offers the underground line and an interval
between 4-6 stations, which is not suficient
 Acceleration and pressure changes are characteristic enough
to count stations
 Pressure Delta between (multiple) stations can additional be
used for absolute positioning
 Very robust for determination of levels (underground stairs,
buildings)
 Currently only two android devices available (Xoom, Galaxy
Nexus)
 Apps, Data and Bachelor Thesis available
Beuth Hochschule für Technik Berlin – University of Applied Sciences 9