Structure: Overview Geocoding Coordinate System Overlays Conclusion Questions November 07 Computational Aspects of GIS Oliver Walzer Analyzing Google Maps Oliver Walzer Computational Aspects of GIS Fall 2007,

Structure: Overview Geocoding Coordinate System Overlays Conclusion Questions November 07 Computational Aspects of GIS Oliver Walzer Analyzing Google Maps Structure Introduction Overview Geocoding Coordinate System Overlays Conclusion Questions

Structure: Overview Geocoding Coordinate System Overlays Conclusion Questions November 07 Computational Aspects of GIS Oliver Walzer Analyzing Google Maps Overview Announced February 8 th, 2005 Beta until October 6 th, 2005 Second API version released April 3 rd, 2006 Geocoding service added June 11 th, 2006 User friendly Fast Public available API

Structure: Overview Geocoding Coordinate System Overlays Conclusion Questions November 07 Computational Aspects of GIS Oliver Walzer Analyzing Google Maps API Overview Cross browser compatible JavaScript based Object oriented Well structured Extensible Comprehensive documentation Key is required

Structure: Overview Geocoding Coordinate System Overlays Conclusion Questions November 07 Computational Aspects of GIS Oliver Walzer Analyzing Google Maps Geocoding Maps an address to a geographic coordinate Interpolation method Limited accuracy Easy to use Used technology hidden Alternatives to Google's Geocoder available

Structure: Overview Geocoding Coordinate System Overlays Conclusion Questions November 07 Computational Aspects of GIS Oliver Walzer Analyzing Google Maps The Coordinate System Datum: WGS84 Projection: Mercator Unit system: Pixels Axes: East, South Origin: International date line, north pole

Structure: Overview Geocoding Coordinate System Overlays Conclusion Questions November 07 Computational Aspects of GIS Oliver Walzer Analyzing Google Maps Mercator Projection Projection of the earth onto a cylinder Invented 1569 by Geradus Mercator Preserves directions Distorts the size

Structure: Overview Geocoding Coordinate System Overlays Conclusion Questions November 07 Computational Aspects of GIS Oliver Walzer Analyzing Google Maps Tiles and Origin Fixed size of 256x256 pixels 2 z tiles per zoom level z Maximal pixel space: 256 * 2 19 Origin shift Invert y

Structure: Overview Geocoding Coordinate System Overlays Conclusion Questions November 07 Computational Aspects of GIS Oliver Walzer Analyzing Google Maps Pros / Cons Prerender tiles Effective caching Easy implementable Simple map overlay Bad accuracy when far north / south Uncommon

Structure: Overview Geocoding Coordinate System Overlays Conclusion Questions November 07 Computational Aspects of GIS Oliver Walzer Analyzing Google Maps Web Map Service OGC standard –Map retrieval –Feature information –Map types Very flexible On the fly map generation Public available map servers

Structure: Overview Geocoding Coordinate System Overlays Conclusion Questions November 07 Computational Aspects of GIS Oliver Walzer Analyzing Google Maps Conclusion User friendly Flexible Great API Easy to integrate into existing applications Capable of being extended Lack of open standards

Structure: Overview Geocoding Coordinate System Overlays Conclusion Questions November 07 Computational Aspects of GIS Oliver Walzer Analyzing Google Maps References Elson, J., Howell, J., & Douceur, J. R. (2007). MapCruncher: Integrating the world's geographic information. SIGOPS Oper.Syst.Rev., 41(2), Gibson, R., & Erle, S. (2006). Google maps hacks Google maps. (2007). Retrieved , 2007, from Google maps deconstructed. (2006). Retrieved , 2007, from deconstructed

Structure: Overview Geocoding Coordinate System Overlays Conclusion Questions November 07 Computational Aspects of GIS Oliver Walzer Analyzing Google Maps References OnEarth. (2006). Retrieved , 2007, from Podnar, H., Gschwender, A., Workman, R., & Chan, J. (2006). Geospatial visualization of student population using google\™ maps. J.Comput.Small Coll., 21(6), USGS earth resources observation and science (EROS). (2005). Retrieved , 2007, from Weisstein, E. W. (2004). Mercator projection. Retrieved , 2007, from

Structure: Overview Geocoding Coordinate System Overlays Conclusion Questions November 07 Computational Aspects of GIS Oliver Walzer Analyzing Google Maps Questions?