Location-aware applications:
an overview
12.3.2013
Content
Part I:
What are Location-Aware Applications?
Examples of LAAs
Part II:
Mapping
Positioning
Part I
Location-aware applications
Background
Key components
Example 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 locationbased 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
alarm unit
Multi-usage
PDA
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
Localization
Locating yourself
Navigation
Navigating through space, planning a route
Identification
Identifying and recognizing persons or objects
Event check
Checking 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 systems
Mapping
Positioning 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
National Land Survey
of Finland
National
mapping
European Union
Continental
mapping
Finland
ETRS89 Europe
Projected coordinate systems
Defines a flat, two-dimensional surface
based on a GCS
Transforms ellipsoid coordinates to flat,
planar coordinates
Three basic techniques
Azimuth
Preserves directions from a central point
Not used near the Equator
Conical
Preserves shapes
Sizes distorted
Used for mid-latitude areas
Cylindrical
Preserves shapes
Sizes distorted
Used for world maps
Projected coordinate systems
Projection
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
References
Part 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