inf245 mobile applications location based services
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Molde University College INF 245 Fall 2007 OBø
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INF245 Mobile applications Location Based
Services
H 2007
Ola Bø
Molde University College INF 245 Fall 2007 OBø
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Location based services Introduction Uses information about the
users position to deliver a service
Valuable for the mobile user Possible services
Emergency services Finding the route Advertise local events and
services Driving force
USA – FCC requires an improved 911-service
Europe E-112 Europe and Asia m-commerce
What if the service will be used somewhere else than current position
1. generation: The user registers position information himself – postal code or city/street Position-dependent content:
driving directions, restaurants, shops, weather
2. generation: Can find position with no user assistance. – low accuracy Similar to 1. generation
3. generation: Accurate positioning with no user assistance Starting services, updated
information from nearby shops and detailed maps, fleet mgmt.
Molde University College INF 245 Fall 2007 OBø
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The E911-service 911 is the US emergency number FCC requires positioning of emergency calls
Position as important as type of emergency Phase 1: done
What tower received the call and caller’s number Phase 2: to be completed by 1.10.2001:difficult
Positioning accuracy 124 m in 67 % of the cases should be 95 % finished by 2005
Consequences Accurate positioning of mobile phones available in the US Many possible applications – will they become reality – Cost,
Privacy legislation Similar initiative in Europe: E112
Molde University College INF 245 Fall 2007 OBø
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Applications using positioning information
Emergency services Traffic information Navigation Service personnel
management Fleet management
Tracking Packages Cars
Wireless advertising Finding services Map services Weather information
Molde University College INF 245 Fall 2007 OBø
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Mobile positioning techniques
Accuracy vs. cost Network based solutions
Cost effective, but inaccurate ~1000 m Works for all handsets
Handset based solutions More expensive and more accurate ~10 m
Mixed solutions
Molde University College INF 245 Fall 2007 OBø
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Network based positioningCell identity The cell is identified But where is the user in the
cell? Accuracy ~1 km
Dependent upon cell size Unusable for many purposes Can be improved
Cell divided into sectors Distance from tower measured
in Timing Advance Combined method: Cell global
Identity-Timing Advance (CGI-TA) Accuracy ~100m
Applications get information from MPC (Mobile Positioning Center)
Higher accuracy in cities than in the countryside – Why?
Molde University College INF 245 Fall 2007 OBø
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Network based positioningTime of Arrival Uses information from three or more
base stations Time for arrival of signal from phone
to base stations is measured Base stations with accurate and
synchronous clocks (expensive) Distance from phone to base
stations is measured With three or more base stations
position can be accurately determined
No handset modification necessary Accuracy ~50 m
30m/300 000 000m/s=0,000 000 1 s maximum deviation between base station clocks
Molde University College INF 245 Fall 2007 OBø
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Hand set based positioningEnhanced Observed Time Difference (E-OTD)
Same solution as for Time of Arrival, but on the handset
The base station sends accurate and synchronized clock signals
Time difference is measured Position is calculated in handset or by
network Requires special handsets
Molde University College INF 245 Fall 2007 OBø
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More possibilities for network/handset- based positioning
Signal strength Relative time difference supported by a
database for the area
Molde University College INF 245 Fall 2007 OBø
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Handset based positioning GPS
Global positioning system 24 satellites in orbit Limitations
requires free sight to at least 3 satellites
trees and buildings block No GPS inside buildings But up to the building
entrance Heavy calculations Takes time to find first
position (20-40s)
Molde University College INF 245 Fall 2007 OBø
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Handset based positioning GPS GPS as a separate unit Now starting to be embedded Falling prices, augmenting
use One Way communication
from satellite Built upon triangulation Accurate ~10 m improved
using D-GPS Can be combined with other
positioning services Assisted GPS (A-GPS)
Calculations performed on server
Satellite information already collected – quicker positioning
Differential GPS solutions can improve accuracy to 10 cm
Molde University College INF 245 Fall 2007 OBø
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Data stream from a GPS
$GPRMC,121430.839,A,6244.1787,N,00706.6071,E,0.12,67.71,041104,,*3C$GPGGA,121431.839,6244.1788,N,00706.6064,E,1,04,3.2,92.9,M,42.7,M,0.0,0000*45$GPGSA,A,3,05,09,30,04,,,,,,,,,4.6,3.2,3.3*3A$GPRMC,121431.839,A,6244.1788,N,00706.6064,E,0.14,136.60,041104,,*05$GPGGA,121432.839,6244.1791,N,00706.6061,E,1,04,3.2,92.4,M,42.7,M,0.0,0000*46$GPGSA,A,3,05,09,30,04,,,,,,,,,4.6,3.2,3.3*3A$GPRMC,121432.839,A,6244.1791,N,00706.6061,E,0.11,144.76,041104,,*0C$GPGGA,121433.839,6244.1788,N,00706.6059,E,1,04,3.2,92.9,M,42.7,M,0.0,0000*49$GPGSA,A,3,05,09,30,04,,,,,,,,,4.6,3.2,3.3*3A$GPRMC,121433.839,A,6244.1788,N,00706.6059,E,0.15,143.11,041104,,*0C$GPGGA,121434.839,6244.1786,N,00706.6055,E,1,04,3.2,93.6,M,42.7,M,0.0,0000*42$GPGSA,A,3,05,09,30,04,,,,,,,,,4.6,3.2,3.3*3A$GPRMC,121434.839,A,6244.1786,N,00706.6055,E,0.18,149.46,041104,,*0C$GPGGA,121435.839,6244.1788,N,00706.6056,E,1,04,3.2,93.5,M,42.7,M,0.0,0000*4D$GPGSA,A,3,05,09,30,04,,,,,,,,,4.6,3.2,3.3*3A$GPGSV,3,1,10,05,71,213,41,09,47,144,36,14,44,281,00,30,40,242,40*7B$GPGSV,3,2,10,07,22,048,00,04,19,086,28,01,13,330,00,20,09,010,00*73$GPGSV,3,3,10,31,08,040,00,24,05,117,00*72
Sentence GGA
Function: Global Positioning Fix Data
Example: $GPGGA,120757,5152.985,N,00205.733,W,1,06,2.5,121.9,M,49.4,M,,*52
Synopsis: time of fix (hhmmss), latitude, N/S, longitude, E/W, Fix quality (0=invalid, 1=GPS fix, 2=DGPS fix), number of satellites being tracked, horizontal dilution of position, altitude above sea level, M (meters), height of geoid (mean sea level) above WGS84 ellipsoid, time in seconds since last DGPS update, DGPS station ID number, checksum
fra http://www.scnt01426.pwp.blueyonder.co.uk/Articles/GPS/NMEA.htm
Molde University College INF 245 Fall 2007 OBø
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EGNOS European Geostationary Navigation Overlay Service
Satellite based augmentation system Supplements the GPS and Galileo*
positioning system reporting their errors to improve accuracy
Started July 2005 2m accuracy, 99% availability
Certified for life critical applications from 2008*Galileo is an European parallel to the GPS
system to be completed by 2011.
Molde University College INF 245 Fall 2007 OBø
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Proximity based positioning
If you are connected you are there! Built upon short range technology
RFID BT WLAN (proprietary solutions to identify the base
station being used)
Molde University College INF 245 Fall 2007 OBø
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Geographic Information Systems GIS Coordinates is not enough GIS gives position information a context GIS can contain a wealth of information
What is where Patterns
Applications What is near by m-commerce Driving directions Emergency messages
In Norway GAB (Grunneiendommer, Adresser og Bygningsmasse) is a developed GIS
GIS a study in it’s own right!
Molde University College INF 245 Fall 2007 OBø
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Geographic information systems Demonstration and Discussion Demonstration
Norgesglasset http://ngis2.statkart.no/norgesglasset/default.html
Visveg http://www.visveg.no/ Gule sider www.gulesider.no Finn http://www.finn.no/finn/map Mappoint http://www.mappoint.com
Drøfting What generation of LBS do the presented services
represent How can the services exploit position information Can the services be interesting in a mobile context as well What must be changed to permit mobile use of the
services?
Molde University College INF 245 Fall 2007 OBø
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Development of location based services
A Market in development A Complex situation Proprietary API for access
Network based API Mobile Positioning Center MPC
Hand set based API Standardization
Location Interoperability Forum under OMA Open Gis Consortium ISO/TC211
Molde University College INF 245 Fall 2007 OBø
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Other solutions
http://www.mapsolutions.no/mapengine.html http://www.opengeospatial.org Ugland IT Statkart
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