[OSM-talk] Google Maps maps most of Europe

Simon Hewison simon at zymurgy.org
Tue Apr 25 14:45:09 BST 2006

Paul Neave wrote:
> As far as competition goes, that's a lot of it:
> http://googlemapsmania.blogspot.com/2006/04/big-news-google-maps-street-maps-for.html
> Also on a similar note, how does Tele Atlas/Navteq gather their street
> map data? Do they use satellite imagery, draw on the map and copy the
> road data into a database or is every single road surveyed in some
> other way?

For the UK, Tele Atlas licenced data from Ordnance Survey, and then 
tweak it to suit their needs, supposedly adding information. They then 
sell their resultant dataset on to people like Google, Route 66, TomTom, 

Google then supplement the data with a licenced copy of the PAF data 
from Royal Mail (to allow postcode lookup), and a licenced copy of 
various aerial photography datasets.

> I'm curious because although OSM is a fantastic initiative, simply
> drawing roads onto a copy of a satellite map seems to be a much
> simpler option that riding round every road on a bike with a GPS ;)

Spot how many times I've used the word "licenced" in the above reply.
Now try and define a way to do what Google Maps do without using the 
word "licenced".

A satellite photo / aerial photo needs accurate aligning with real 
features on the ground, and factors like the focal length of the lens 
need correcting, which is all quite a lot of work, and companies like 
getmapping.com spend a lot of time making their aerial photography 
dataset align nicely with the real world, so they can licence it to 
other companies (like Multimap). The only freely distributable satellite 
photography dataset that we know about is the NASA LANDSAT dataset, 
which openstreetmap already uses, and is often up to 50m out of 
alignment with reality, and isn't really good enough for urban streets.

Simon Hewison

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