Location-aware applications: an overview

12.3.2013

Content

Part I:What are Location-Aware Applications?Examples of LAAs

Part II:MappingPositioning

Part I

Location-aware applicationsBackground Key componentsExample apps

Location-aware application

Location

Determines user's location

Information

Provides information spatially related to user's location

Interaction

Offers two-way interaction with the information

Location-aware application

Location

Determines user's location

Information

Provides information spatially related to user's location

Interaction

Offers two-way interaction with the information

Location-aware application

Location

Determines user's location

Information

Provides information spatially related to user's location

Interaction

Offers two-way interaction with the information

Terminology

Location-Based Service (LBS)

Conceptually same as LAA

Used in less technically oriented context

Geographic Information System (GIS)

A system for storing and manipulating location-based data

Are used for building LAAs

GIS vs. LBS/LAA

GIS LBS/LAA

Evolution during several decades quite recently

User groups experienced users non-professional users

Functionality wide collection of functionality limited functionality

Requirements extensive computing resources restrictions of mobile computing environment (computational power, small battery run time)

LBS as an intersection of technologies

Devices

Single-usage

Multi-usage

tolling unit

PDA

alarm unitnavigation

system

smart phone

tablet

Limitations

Computing and memory resources

- Top tablets and mobile phones have 1.5-2.0 GHz dual-core or quad-core processor

- Average devices have approx. 1 GHz single core processor and 512 MB / 1 GB RAM

- Mobile architecture is optimized for low power consumption

- Modern mobile operating systems allow applications to run in background, but with a lot of limitations

Limitations

Battery power

- Intensively using internet (3G or WLAN) along with GPS discharges a full battery in 3-5 hours

- Intensively using battery heats up the device

Limitations

Small displays

- Smartphone have 3”-4.5” displays

- Tablets have 7”-10” displays

- Most of the displays are difficult to read in sunlight

Limitations

Access to communication networks

- 3G/4G coverage is not everywhere

- Even GSM is not available everywhere

- WLAN access for positioning lacks outside bigger cities

Limitations

Weather influences on usability

- Most of the devices are not waterproof

- Most of the displays are difficult to read in sunlight

- Touchscreen devices are difficult to use in low temperatures (touchscreen gloves are not warm enough for -20°C)

Photo: www.leavemetomyprojects.com

Communication networks

Positioning technologies

Content providers

How to use?

Where am I? Where are my friends? What is here around me?

User actions

LocalizationLocating yourself

NavigationNavigating through space, planning a route

IdentificationIdentifying and recognizing persons or objects

Event checkChecking for events; determine the state of target

Categories of LAAs

Navigation (automotive routing systems)

Information (location-based yellow pages)

Tracking (wildlife tracking)

Games (capturing the flag)

Emergency (personal alarm units)

Advertising (location-based SMS)

Billing (automotive tolling units)

Management (inmate tracking systems)

Navigation

GoogleMaps(link)

Nokia Transport

(link)

Services and recommendations

TripAdvisor(link)

Yelp(link)

Tracking

Sports tracker

(link)Endomondo

(link)

Social networking

Facebook places(link)

FourSquare(link)

Games

Shadow Cities(link)

O-Mopsi(link)

Augmented reality

Layar(link)

Nearest Subway

(link)

Part II

Coordinate systemsMappingPositioning technologies

Coordinate systems

Used to pinpoint a location on the Earth

A set of numbers or letters

Geographic or projected

Spherical or planar

Geographic coordinate system

Uses a three-dimensional ellipsoid surface

Ellipsoid defines the size and shape of the Earth model

A point is referenced longitude and latitude (angles measured from the earth's center to a point on the earth's surface)

Reference ellipsoid

The shape of the Earth is not symmetric A reference ellipsoid can be used as an approximation

International and national standards used

Geographic coordinate systems (GCS)

Different ways to fit an ellipsoid to the surface of the Earth → many different GCSs

Name Context Organization Usage

WGS84 Global US Department of Defense

GPS

KKJ Finland National Land Survey of Finland

National mapping

ETRS89 Europe European Union Continental mapping

Projected coordinate systems

Defines a flat, two-dimensional surface based on a GCS

Transforms ellipsoid coordinates to flat, planar coordinates

Three basic techniquesAzimuthPreserves directions from a central pointNot used near the Equator

ConicalPreserves shapesSizes distortedUsed for mid-latitude areas

CylindricalPreserves shapesSizes distortedUsed for world maps

Projected coordinate systemsProjection Type Property

Mercator Cylindrical Preserves directions

Used in most applications: • Google Maps• OpenStreetMaps

Gall-Peters Cylindrical Preserves areas

Azimuthal equidistant

Azimuthal Preserving distances

Equirectangular Cylindrical Compromises

http://en.wikipedia.org/wiki/List_of_map_projections

Distance

The Haversine formula

Positioning technologies

Cell tower triangulation and cell ID databases

Satellite navigation

Wireless positioning systems

Cell tower triangulation

More cell towers available = better accuracy

Low accuracy where are few cell towers (1-20 km)

Accuracy in cities approx. 50-200 meters

No altitude information

Cell ID databases

Each base transceiver station has an unique ID

Mobile device gets associated with the BTS it is connected to (usually the nearest one)

Approx. of the location can be known by using a database for BTS IDs

Satellite navigation (GPS)

De facto standard for positioning in LBS

Controlled by US Department of Defense

Can be enhanced by additionally using Glonass (Russia) or Galileo (EU, in development)

Accuracy 5-50 meters

Does not work indoors

GPS accuracy test (2009)

Nokia 6110 2.73m

Nokia N95-2, cover open 3.13m

Nokia N95-1 + external (Pretec) 3.61m

Garmin wrist-GPS (1s.) 3.69m

Garmin wrist-GPS (8s.) 3.75m

Nokia E72 3.76m

Nokia E66 5.10m

Nokia N95-2, cover closed 6.05m

Nokia N95-2 + external (Fortuna) 6.44m

Assisted satellite navigation (aGPS)

Combines GPS with cell tower triangulation and other techniques

Speeds up the process, especially time to first fix

Improves accuracy

Uses additional data downloaded from a server to improve accuracy

Still does not work indoors

Wireless positioning systems

Same logic as in cell ID positioning

Uses wireless routers, corresponding IDs and databases

Popular before GPS chips became common

Example: Google Maps cars record positions of wireless networks with recording Street View data

Comparison of positioning technologies

Method Pros Cons

Cell tower triangulation

- works indoors- works globally (western world)- pretty accurate in cities (100 m)

- inaccurate in rural areas (1-10 km)

Cell ID database

- no receiver needed on device- works globally (western world)- good accuracy in cities

- 3rd party database needed for IDs- inaccurate in rural areas

Global Positioning System

- works globally (rural & city)- good, consistent accuracy (10 m)- commonly supported

- doesn't work indoors- weak accuracy in cities ('canyon effect')- consumes battery life- slow initialization (30-60 s)

Assisted GPS

- speeds up initialization- improves accuracy

- not commonly supported on devices other than smart-phones- lack of standards- requires internet connection

Wireless positioning

- works indoors- accurate in cities

- WiFi receiver needed on device- doesn't work in rural areas or areas without WiFi- 3rd party database needed for IDs

ReferencesPart I:S. Steiniger, M. Neun and A. Edwardes:Foundations of Location Based Services (link) Used with permission from the authors

Part II:ICSM: Fundamentals of Mapping (link)CC BY 3.0 AU