Structure: Overview Geocoding Coordinate System Overlays Conclusion Questions November 07...

Structure:

Overview

Geocoding

Coordinate System

Overlays

Conclusion

Questions

November 07Computational Aspects of GIS

Oliver Walzer

Analyzing Google Maps

Analyzing Google Maps

Oliver WalzerComputational Aspects of GISFall 2007, 12.11.2007

Structure:

Overview

Geocoding

Coordinate System

Overlays

Conclusion

Questions

November 07Computational 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 07Computational Aspects of GIS

Oliver Walzer

Analyzing Google Maps

Overview

• Announced February 8th, 2005• Beta until October 6th, 2005• Second API version released April 3rd, 2006• Geocoding service added June 11th, 2006• User friendly• Fast• Public available API

Structure:

Overview

Geocoding

Coordinate System

Overlays

Conclusion

Questions

November 07Computational 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 07Computational 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 07Computational 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 07Computational 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 07Computational Aspects of GIS

Oliver Walzer

Analyzing Google Maps

Tiles and Origin

• Fixed size of 256x256 pixels• 2z tiles per zoom level z• Maximal pixel space: 256 * 219

• Origin shift• Invert y

Structure:

Overview

Geocoding

Coordinate System

Overlays

Conclusion

Questions

November 07Computational 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 07Computational 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 07Computational 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 07Computational Aspects of GIS

Oliver Walzer

Analyzing Google Maps

ReferencesElson, J., Howell, J., & Douceur, J. R. (2007). MapCruncher: Integrating the world's geographic information. SIGOPS Oper.Syst.Rev., 41(2), 50-59.

Gibson, R., & Erle, S. (2006). Google maps hacks

Google maps. (2007). Retrieved 12.11.2007, 2007, from http://docs.codehaus.org/display/GEOSDOC/Google+Maps

Google maps deconstructed. (2006). Retrieved 12.11.2007, 2007, from http://cfis.savagexi.com/articles/2006/05/03/google-maps-deconstructed

Structure:

Overview

Geocoding

Coordinate System

Overlays

Conclusion

Questions

November 07Computational Aspects of GIS

Oliver Walzer

Analyzing Google Maps

ReferencesOnEarth. (2006). Retrieved 12.11.2007, 2007, from http://wms.jpl.nasa.gov/

Podnar, H., Gschwender, A., Workman, R., & Chan, J. (2006). Geospatial visualization of student population using google\™ maps. J.Comput.Small Coll., 21(6), 175-181.

USGS earth resources observation and science (EROS). (2005). Retrieved 12.11.2007, 2007, from http://gisdata.usgs.gov/

Weisstein, E. W. (2004). Mercator projection. Retrieved 12.11.2007, 2007, from http://mathworld.wolfram.com/MercatorProjection.html

Structure:

Overview

Geocoding

Coordinate System

Overlays

Conclusion

Questions

November 07Computational Aspects of GIS

Oliver Walzer

Analyzing Google Maps

Questions?