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Location Based Services: A Gentle Introduction

Location Based Services: A Gentle Introduction. Presented to: Computer Science 1001 By Shashi Shekhar Computer Sc. Faculty University of Minnesota May 2 nd , 2007. Source: http://www.northwoodssurvival.com/content/navigation_class.jpg. Outline. Introduction What are LBS?

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Location Based Services: A Gentle Introduction

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  1. Location Based Services: A Gentle Introduction Presented to: Computer Science 1001 By Shashi Shekhar Computer Sc. Faculty University of Minnesota May 2nd, 2007 Source: http://www.northwoodssurvival.com/content/navigation_class.jpg

  2. Outline • Introduction • What are LBS? • How are LBS useful? • How does it work? • What’s special about it? • Where to go next?

  3. Introduction • Q? watched any of the following movies? • Batman, Mission Impossible, • Spy Kids 2: The Island of Lost Dreams • Minority Report • GPS • … • Ex. What LBS are featured in these movies? • GPS – The Movie • A group of adventure seeking college kids • embark on a GPS treasure hunt in the • Northwest wilderness. • http://www.gpsthemovie.com/

  4. LBS - Examples • Q? Have we used the following ? • E.g.: MapQuest, Google Maps, … • Q? Are these location-based services ? Courtesy: Microsoft Live Search (http://maps.live.com)

  5. Navigation Devices • Cell-phone, watch, custom • For in-vehicle or portable use

  6. Outline • Introduction • What are LBS? • How are LBS useful? • How does it work? • What’s special about it? • Where to go next? Source:www.gamma-project.info/images/lbs.jpg

  7. What is LBS? - Wikipedia Perspective

  8. What are LBS? • Cell-phone-centric definition • a way to send custom advertising and other information to cell-phone subscribers based on their current location (Wikipedia) • Generalized definition • Service customized to given locations • It begs 3 questions! • Which Location? • Individual’s current location • Or favorite locations, e.g. home, work, … • Or Specified location, e.g. a travel destination • Group of individuals and their locations (?) • What implicit spatial relationship to given location? • Identify service instances near given location(s) • Neither far nor near given location(s) • Which Service?

  9. Suspenseful, terrifying, full-length film about a 30' trimaran's capsize due to poor seamanship in a big storm while on its way from Vancouver, Canada to Costa Rica. The 74-day survival efforts … Based on a true story. (Source: www.multihullsmag.com) Outline • Introduction • What are LBS? • How are LBS useful? • How does it work? • What’s special about it? • Where to go next?

  10. Measuring motion and deformation of Earth Source: wwwrses.anu.edu.au/~anya/polenet/science_gps.htm Source:www.where2getit.com/products/ Outline • Introduction • What are LBS? • How are LBS useful? • How does it work? • What’s special about it? • Where to go next?

  11. How are LBSs useful? • Numerous Applications • Emergency Service • Public Safety – E911, Crime Mapping • Security – Reverse 911, Evacuation Routes • Information Services • Location-based Search – nearest facility • Routing, Navigation – commuters, travellers • Social Networks • Location-based friend search • Smart mobs • Commerce • Location based billing, content-push, … • Asset tracking, Facilities Management • Science • Tracking animal habitat, migration, … ?Future? GPS Collar, Implantable GPS chip Sources: www-research.ge.ucl.ac.uk/bear/htm/prtns/va.html , www.gpsworld.com/gpsworld/article/articleDetail.jsp?id=360842

  12. Source: http://people.hofstra.edu/geotrans/eng/ch7en/meth7en/hufflaw.html Business Applications • Business Questions • Predicting consumer spatial behaviors • Delineating trade / service areas • Analyzing market performance by regions • Locating retail and service facilities • Huff model [1963] : utility = f ( square footage / distance )

  13. Location Based Patterns and Scientific Discoveries • The 1854 Asiatic Cholera in London • Precursor to germ theory

  14. Location based service in Public Health • Sample Local Questions from Epidemiology [TerraSeer] • What’s overall pattern of colorectal cancer • Is there clustering of high colorectal cancer incidence anywhere in the study area • Where is colorectal cancer risk significantly elevated • Where are zones of rapid change in colorectal cancer incidence Geographic distribution of male colorectal cancer in Long Island, New York (Courtesy: TerraSeer)

  15. Critical locations in Climatology • Teleconnection • Find (land location, ocean location) pairs with correlated climate changes • Ex. El Nino affects climate at many land locations • Precursor to global warming theories Global Influence of El Nino during the Northern Hemisphere Winter (D: Dry, W: Warm, R: Rainfall) Average Monthly Temperature (Courtsey: NASA, Prof. V. Kumar)

  16. Location brings context and aids understanding! • Location helps bring rich contexts • Physical: e.g., rainfall, temperature, and wind • Demographical: e.g., age group, gender, and income type • Problem-specific, e.g. distance to highway or water • Understanding of a physical phenomenon • Though, final model may not involve location • Cause-effect e.g. Cholera caused by germs • Discovery of model may be aided by spatial patterns • Many phenomenon are embedded in space and time • Ex. 1854 London – Cholera deaths clustered around a water pump • Spatio-temporal process of disease spread • => narrow down potential causes • Ex. Recent analysis of SARS

  17. Technology Risks Source: http://archive.salon.com/comics/tomo/2001/07/09/tomo/index.html, www.gpsworld.com/gpsworld/article/articleDetail.jsp?id=360842

  18. Outline • Introduction • What are LBS? • How are LBS useful? • How does it work? • What’s special about it? • Where to go next? Navstar ii GPS Satellite Navigation System using Timing And Ranging (Source: www.spacetoday.org/Satellites/GPS.htm)l

  19. How does GPS work? • GPS Receiver • listens to 3 or more satellites • Uses triangulation algorithm • To estimate position • Challenges • Multi-path reflections • Obstructions • overbridges, skyscrapers • Leads to errors • Typical accuracy • Basic GPS - Few meters • Differential GPS – sub-meter Source: GPS Explained www.kowoma.de/en/gps/positioning.htm

  20. How does it work? • How does GPS determine locations ? • How does LBS software work ? • What if need more sophisticated spatial reasoning ?

  21. How does LBS Software work ? • Buy or Build? • Reusable Libraries are becoming available • Open standards emerging • Ex. Open Location Services – Core Services • Directory Service • online directory (e.g., Yellow Pages) to find the location of a specific or nearest place, product or service. • Gateway Service • fetches the position of a known mobile terminal • Location Utility Service provides • Geocoder : place name  coordinates • Example: Street address  (latitude and longitude) • Reverse Geo-coder: coordinates  place name • Presentation Service portrays a map • a base map derived from any geospatial data • and a set of Abstract Data Types as overlays • Route Service • determines travel routes and navigation information between two or more places

  22. Standards: OGC • What if my application needs more spatial sophistication? • Ex. Reasoning with extended geographic features • Q? List restaurants in Minneapolis near rivers or lakes. • Open GIS Consortium – Simple Features Model • Basic spatial data types: e.g. point, line, polygons • Several spatial operations on these spatial data types Examples of Spatial Operations in OGC Model

  23. Mashups: Location Based Web-Services

  24. Mashups: Location Based Web-Services • Simple APIs • Google Earth – KML • Microsoft Virtual Earth SDK • Example Code: KML (Source:http://www.econym.demon.co.uk/googlemaps/kml.htm) <?xml version="1.0" encoding="UTF-8"?> <kml xmlns="http://earth.google.com/kml/2.0"> <Document> <name>KML Example file</name> <description>Simple markers</description> <Placemark> <name>Marker 1</name> <description>Some stuff to put in the first info window</description> <Point> <coordinates>-122.1,37.4,0</coordinates> </Point> </Placemark> </Document> </kml>

  25. What is special about LBS? • Introduction • What are LBS? • How are LBSs useful? • How does it work? • What’s special about it? • Where to go next? Source:http://ssnds.uwo.ca/sscnetworkupdate/2006winter/images/gis.jpg

  26. Data in Location Based Services • Non-spatial Information • Same as data in traditional data mining • Numerical, categorical, ordinal, boolean, etc • e.g., city name, city population • Spatial Information • Spatial attribute: geographically referenced • Neighborhood and extent • Location, e.g., longitude, latitude, elevation • Spatial data representations • Raster: gridded space • Vector: point, line, polygon • Graph: node, edge, path Raster Data for UMN Campus Courtesy: UMN Vector Data for UMN Campus Courtesy: MapQuest

  27. Spatial Relationships • Relationships Categories • Set-oriented: union, intersection, membership, etc • Topological: meet, within, overlap, etc • Directional: North, NE, left, above, behind, etc • Metric: e.g., Euclidean: distance, area, perimeter • Graph-based: shortest path • Shape-based and visibility • … • Granularity

  28. Mathematical Foundations – Topological Operations • Topology • 9-intersections using • Interior • boundary • exterior Q? Define 9-intersection for following operations: inside.

  29. Spatial Autocorrelation (SA) • First Law of Geography • “All things are related, but nearby things are more related than distant things. [Tobler, 1970]” • Spatial autocorrelation • Nearby things are more similar than distant things • Traditional i.i.d. assumption is not valid • Measures: K-function, Moran’s I, Variogram, … Pixel property with independent identical distribution Vegetation Durability with SA

  30. Location Prediction – Spatial Statistics vs. Classical Statistics! Nest Locations Vegetation Water Depth Distance to Open Water

  31. Spatial Discontinuities may be anamolous • Spatial Outliers • Traffic Data in Twin Cities • Abnormal Sensor Detections • Spatial and Temporal Outliers

  32. What is special about LBS? • Introduction • What are LBS? • How are LBSs useful? • How does it work? • What’s special about it? • Where to go next? Source: http://qcpages.qc.cuny.edu/career/Career/pictures/assessments/newRoadmap5.jpg

  33. Where to go next? • Books • Courses at the U • Web-sites • www.spatial.cs.umn.edu • www.geog.umn.edu/umucgis/ • www.opengis.org

  34. Spatial Thinking Across Disciplines

  35. Courses at U of M

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