7.3 Technical Background of Determining Position 1937.3 Technical Background of Determining Position
If you access the website http://www.google.com from abroad, you may be
surprised to find that you are automatically redirected to the relevant Google
domain of the country you are in. This works even if your browser is not geolo-
cation capable: Google uses a simple trick and locates your whereabouts via the
IP address.
Browsers supporting the Geolocation API can achieve a significantly greater ac-
curacy by making use of other technical options. The following four methods are
currently in use:
- In PCs with wired Internet connections, the position is located via the
IP address. This way of determining position is rather inaccurate, as you
would expect. - The position can be determined much more precisely if there is a wireless
LAN connection. Google has collected data worldwide from public and
private WLANs. - If the hardware has a mobile communications chip (for example, in
a smartphone), it tries to calculate the position within the mobile
communications network. - If the hardware also has a GPS sensor, the position can be determined
even more accurately. GPS is a satellite-based positioning system and can
achieve accuracy to the meter range even with cheap sensors, provided the
conditions are favorable (outside of buildings, unobstructed horizon, etc.).
Only the GPS sensor works offline; methods 1–3 require Internet access and
are implemented through a server location service. These services are available
from Google (Google Location Service, used in Firefox, Chrome, and Opera) and
another American company, Skyhook Wireless (used in Safari and early versions
of Opera).
But how do the service providers get the location information of wireless and
mobile networks? In parallel with the photos taken by Google for the service
Street View, the Google Street View vehicles also save information on public and
private WLANs. The revelation, in spring 2010, that these vehicles collected not
only the MAC address and SSID of the WLAN, but also user data, shed a bad light
on Google, resulting in several public apologies.
But that is not all: If the browser has access to the information on a mobile net-
work or wireless LAN router, this data is sent with every call of the service. For
Google, this concerns mainly mobile communication devices with the Android
operating system; Skyhook profits from the iPhone users. The combination of
the described methods leads to a very large data set of geodata available to these
two service providers and is continuously updated through crowdsourcing (even
if the users as data providers do not know anything about it).