location-aware applications: an overview 12.3.2013
TRANSCRIPT
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