inf245 mobile applications location based services

Molde University College INF 245 Fall 2007 OBø

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INF245 Mobile applications Location Based

Services

H 2007

Ola Bø


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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.


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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


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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


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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


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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?


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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


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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


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More possibilities for network/handset- based positioning

Signal strength Relative time difference supported by a

database for the area


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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)


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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

http://www.finn.no/finn/map


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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


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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.


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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)


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Telenor’s positioning product


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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!


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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?

http://ngis2.statkart.no/norgesglasset/default.html

http://www.visveg.no/



http://www.gulesider.no/




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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


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Other solutions

http://www.mapsolutions.no/mapengine.html http://www.opengeospatial.org Ugland IT Statkart

http://www.mapsolutions.no/mapengine.html

http://www.mapsolutions.no/mapengine.html

http://www.opengeospatial.org/

http://www.opengeospatial.org/

inf245 mobile applications location based services

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