What are the sources of excellent geo-location data as possessed by Google Maps ?
I am wondering that, even with large amount of volunteer work involved, why is OSM data not comparable to theirs in terms of quality ?
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Haklay, M. (2010), How good is volunteered geographical information? A comparative study of OpenStreetMap and Ordnance Survey datasets. Environment and Planning B: Planning and Design 37(4) 682 – 703.
for more rigorous assessment (in UK context).
This one for assessment (in comparison wth Google Maps & Bing Maps) in Ireland:
Ciepłuch , B., Jacob, R.,Mooney, P., Winstanley, A. (2010) Comparison of the accuracy of OpenStreetMap for Ireland with Google Maps and Bing Maps. Proceedings of the Ninth International Symposium on Spatial Accuracy Assessment in Natural Resuorces and Enviromental Sciences 20-23rd July 2010 . p. 337.
And this for assessment in France (paywall):
Girres, J.-F. & Touya, G. (2010) Quality Assessment of the French OpenStreetMap Dataset. Transactions in GIS, 14, 435-459.
Germany is covered in this paper:
Zielstra, D., Zipf, A. (2010) Quantitative Studies on the Data Quality of OpenStreetMap in Germany. Paper presented at GIScience 2010.
Very thorough comparison with TomTom data (in Germany as well) is covered here:
Helbich, M., Amelunxen, C., Neis, P. (2012): Comparative Spatial Analysis of Positional Accuracy of OpenStreetMap and Proprietary Geodata. Int. GI_Forum 2012. Salzburg. Austria.
German street network is also discussed in detail here:
Neis, P.; Zielstra, D.; Zipf, A. (2012) The Street Network Evolution of Crowdsourced Maps: OpenStreetMap in Germany 2007–2011. Future Internet 4, 1-21.
There also two Master's dissertations dealing with this topic: one from UCL:
Kounadi, O. (2009) Assessing the quality of OpenStreetMap data.
and one presented at GI_Forum:
Stark, H-J. (2010) Quality assessment of crowdsourced geocoded address-data within OpenAddresses
Also article from Cartographica (paywall) might be of interest:
Mondzech, J. & Sester, M., (2011) Quality Analysis of OpenStreetMap Data Based on Application Needs. Cartographica: The International Journal for Geographic Information and Geovisualization, 46, 115-125.
It depends how you define quality:
Quality as Currency - In many areas OSM is more current than commercial operations. However the level of currency is not necessarily known. Commercial mapping operations will typically publish periodic updates.
Quality as precision - The precision of data depends on what the mapping is intended to be used for. Large scale topographic mapping is likely to be of much higher precision than equivalent OSM data. The precision of OSM data is by its very nature more variable.
Quality as completeness - In some areas such as developing countries OSM is much more complete. Where commercial data is available it will typically be more complete than the equivalent OSM data, but only within the specification defined by the surveyors.
OSM and commercial mapping data can be compared in terms of objective measures. Quality is too broad a term, and always depends on what you want to do with the data.
Google do not produce geo-location data: they only publish these data. The data source is displayed at the bottom right corner:
Why these data are better compared to OSM data? Professionals products are usually more expensive but better than the amateur ones.
If you live in the US you will often find that now that Google has switched to using it's own data instead of Navtech's that the quality of Google maps is way behind OSM for the same area. Google's appears to be an import from US Govt sources (TIGER, USGS etc) but with out the volunteer fixes that that OSM has benefited from.
Actually I think in most places in the US Google us using their own data that they collected when making streetview. I've actually found it is the best source in a few places, position and address/routing. It's the only service that gets to my house....
Most street data started from the Census data, ex Navtec. Even OSM imported the census data. Had the census saw (in those days) that their data was to be used as it has been, I wonder if they would have done a better job.