SmartCampusAAU APP

- Enabling Ubiquitous Positioning and Navigation Through Crowdsourcing

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Motivation• GPS positioning and navigation has become commonplace, but

GPS has severe problems inside buildings:– GPS positions estimates are very coarse. – There is no semantic information, i.e., information about rooms,

escalators, printer facilities, etc. – There is no indoor navigation.

• The SmartCampusAAU app addresses these shortcomings by providing indoor positioning based on user contributions and Wi-Fi technology:– Positioning accuracy can be as good as three meters, depending on a

variety of factors, including the amount of data supplied by users. – There is semantic information (if users have supplied this)– There is indoor navigation (if users have enabled this)

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Indoor Positioning via Wi-Fi• SmartCampusAAU uses Wi-Fi technology when GPS signals are absent. • Wi-Fi infrastructures are ubiquitous and Wi-Fi is available in modern Smartphones• This means that indoor positioning and navigation can be made available in any

building to any user (carrying a Smartphone).• However, indoor positioning is hard: When Wi-Fi signals are transmitted from an

access point, they are attenuated, scattered and reflected by obstacles like walls, furniture and even people.

• The result is highly unpredictable signal propagations which means that traditional lateration techniques have difficulties in providing accurate position estimates

• Instead, the most accurate technique is called location fingerprinting. • The location fingerprinting technique is based on measuring actual signal strengths

from access points. • The location fingerprinting technique is able to provide location estimates within 3

meters of a user’s actual position.

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How Location Fingerprinting works

• Location fingerprinting is split into two phases:– Offline:

• In order to make indoor positioning possible, a so-called radio map must first be built.

• A radio map is a database that contains signal strength information for different coordinates throughout a building.

• A radio map is incrementally built in the following way: – A user stands at a certain location and marks her location on a map. – The user then starts measuring signal strengths for about 10 seconds. – Finally, the <location, measurement> information is saved in a server-side radio map.

• This process is repeated at different locations until the entire indoor environment has been covered by measurements.

– Online: • If a radio map has been built, indoor positioning is now enabled. • A user can be estimated by the system to be at any of the locations where users

have measured signal strengths in the offline phase.

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Location Fingerprinting- The Offline Phase

AP1

AP3

AP3

AP1 = -40AP2 = -70AP3 = -95

(x1, y1, z1)

AP1 = -45AP2 = -60AP3 = -85

AP1 = -65AP2 = -55AP3 = -75AP1 = -80AP2 = -45AP3 = -60

(x2, y2, z1)

…

(x3, y3, z1)

(x4, y4, z1)

(…)

Radio MapSignal strengths are measured at the starred locations

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Location Fingerprinting- The Online Phase

AP1

AP3

AP2

AP1 = -55AP2 = -40AP3 = -80

(x1, y1, z1)

AP1 = -40AP2 = -60AP3 = -95AP1 = -40AP2 = -70AP3 = -85AP1 = -35AP2 = -90AP3 = -55

(x2, y2, z1)

…

(x3, y3, z1)

(x4, y4, z1)

(…)

Radio Map

AP1 = -50AP2 = -40AP3 = -85

The user can be estimated to be at any of the starred locations

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SmartCampusAAU

• The SmartCampusAAU app implements the location fingerprinting technique as described on the previous pages.

• In the offline phase, the SmartCampusAAU app can be used to build a radio map.

• Moreover, in the offline phase users can build a graph of the indoor environment (establishing links between locations).

• The graph can be used to enable indoor navigation. • (The graph is also used to improve the positioning accuracy) • In the offline phase, users can also supply semantic

information about locations.

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Walkthrough of the SmartCampusAAU app

• The SmartCampusAAU app can be used to enable indoor positioning in a building via the location fingerprinting technique.

• The remaining pages details how this is accomplished. • First, we describe the offline activities that are required to enable the

online positioning and navigation functionality: 1. Add a building and building floors (this only needs to be done once)2. Build a radio map – to enable indoor positioning3. Supply semantic (i.e., human readable) information. 4. Build a graph – to enable indoor navigation

(The ”Offline Mode” is accessed by choosing MENU->Offline Mode when the app starts)

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1-a) Add new building

(1) (2) (3)

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1-a) Add a new building

• The very first step is to add a new building to the system

• This is only needs to be done once (when no radio map exists) by the very first contributor.

1. A building should be given a readable name, e.g., ”Empire State Building” and an optional (official) url.

2. The building should then be positioned globally by marking its location on Google Maps.

3. The system will suggest an appropriate address.

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1-b) Add/Edit building floors

Edit Floor

New Floor

(1) (2)

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1-b) Add/edit building floors

• The second step is to add floors to the building• Even if a building only has one floor it must still be added

to the system. • In the Offline Mode, choose MENU -> Edit Graph -> Edit

Building Floors. This will bring up screen (1). 1. This shows the floors that have been added to the

system. You can now either: 1. Add a new floor2. Edit an existing floor

2. When adding or editing a floor it must be given a floor number as well as a floor name.

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2-1) Add measurement (extend or update the radio map)

Add measurement to new location Add measurement to existing location

(1) (2)

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2-1) Add measurement (extend or update the radio map)• When you are in the Offline Mode you can see a number of icons –

these icons represent the places where other users have measured signal strengths (and hence, locations where the system can estimate users to be).

1. You can add a new location to the radio map by clicking a location on the map and choosing MENU-> Measure. • You can fine-tune the location by choosing MENU->Enable D-pad. This will

give you a little joystick to nudge the location up, down or sideways. • Make sure that you have choosen the correct floor (MENU-> Change

Floor)

2. You can also update an existing location by clicking its icon and choosing ”New Measurement”. Updating existing locations will help to continuously improving the positioning accuracy of the system.

• IMPORTANT! Make sure you stand in the location you marked on the map.

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2-2) Measuring signal strengths

(1) (2) (3)

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2-2) Measuring signal strengths• When you have opted to measure signal strengths at a location you are brought to

screen (1) on the preceeding page. • It is important that you remain in the position that you marked on the map during

the measurement process. 1. You start a measurement by clicking the ”Start” button.2. This will will up a dialog that shows the number of Wi-Fi scans that have

currently been performed. – The measurement process is stopped by clicking ”Stop”.– The more scans you take before click ”stop” the better. We recommend a

minimum of 10 scans, but even more scans will have a beneficiel effect on the positioning accuracy of the system.

3. When the measurement process is done a list of access points that could be heard is shown. – If you know that some access points do not belong to the building, please

unmark them. Otherwise, just leave all access points marked. – The final step is to save the measurement by clicking the ”Upload Selected”

button.

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3) Add semantic information

(1) (2) (3)

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3) Add semantic information• When a new location has been added to the radio map you will notice that it is

represented by a ?-icon on the map. • This means that the system is now able to position users at that location. • You can also associate semantic information (i.e., human readable information) by

clicking on the location and choosing ”Edit Location”. This will bring you to screen (1) on the preceeding page.

1. You can specify the following details for a location: Title, description and url for the location. You should mark the field ”Is Entrance” if the location represents an entrance into the building

2. You can specify some properties for the location (e.g., whether the location is an office, lecture room, etc.). This will be reflected in the icon that is shown for the location

3. This shows an example of having added semantic information to a location. The location’s title is ”Canteen”, the description says ”Open 11-13” and there is a URL which will show further details for canteen. The location was marked as ”Food” which shows in the icon.

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4) Add links

(1) (2) (3)

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4) Add links• In order to enable indoor navigation you need to add links between

neighbouring locations where it is physically possible to move between.• In the Offline Mode you choose MENU->Edit Graph->Edit Links. 1. You add a link by clicking on two neighbouring locations that are not yet

connected and then choose MENU->Add Link. This will bring you to screen (2)

2. On this screen you specify properties for the link. ”None” means that there are no special properties; otherwise you can indicate whether the locations are connected via an elevator or stairs.

3. This shows a link that is now connection two locations.

• The procedure for removing a link is identical except you should click on two locations that are already connected and then choose MENU->Remove Link.

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Online Mode

• Assuming the four steps in the Offline mode have been done, indoor positioning and navigation is now enabled in the building.

• When the SmartCampusAAU app starts up it is in the online mode where indoor positioning and navigation functionality can be used.

• The following pages demonstrate the online functionality.

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Indoor Positioning – Choose Provider

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Indoor Positioning – Choose Provider

• In MENU->Choose Provider you can choose between different location providers:– GPS: Uses GPS for positioning. Appropriate for outdoor

usage. – Wi-Fi: Uses Wi-Fi (location fingerprinting) for positioning.

Appropriate for indoor usage. • When switching to Wi-Fi, the system will detect and download an

appropriate radio map and then start positioning. The system will automatically change floors when the user’s current location changes floor.

– None: Turns off positioning. Appropriate for saving energy when positioning is not needed.

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Online Options

• MENU contains the available online options

• You can see which points of interest are available on the current floor, you can search for points of interest, and you can change floor.

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Tracking Position On/Off

Tracking enabled Tracking disabled

Tracking means that the the map will center around the user’s current position.Tracking can be disabled by panning on the map or changing floor from the menu. Also, the tracking button in top left corner can be used to enable/disable tracking

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Navigation

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Summary

• The SmartCampusAAU app relies on end user participation (aka crowdsourcing) to enable indoor positioning and navigation.

Users enable indoor positioning via location fingerprinting

Users enable indoor navigation by adding links between locations.

Users supply semantic information about indoor locations