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GPS finds out
the location based on the concept of Trilateration, a fundamental
geometric principle that allows people to find one location if its
distance from other known locations is known.y7yhn
Figure
2
: GPS Concept of
Trilateration
Picture Courtesy: how stuff works.com
GPS is proved
to be accurate and useful enough for many years. However, it is not
good enough for LBS uses. The main problem is that to use GPS, the
mobile device should be in sight of those satellites. This is hardly
possible in indoor environment or urban areas with tall buildings,
where LBS is mainly used. GPS is not accurate and fast enough for
demanding LBS uses. Since it cannot provide locations as precise as
street level, and it could take several minutes to achieve an
accurate location under undesirable environment.
Network based
Cell ID
In a mobile
network, each base station has a cell ID. Whenever a mobile phone is
switched ‘ON’, the phone gets connected to one of these cells to
register itself with the cellular network. By knowing the phone’s
current cell an approximate location of the phone can be calculated.
However many
question the usefulness of cell ID in LBS applications since the
accuracy of the location is very low. Patrick Bossert (2002) for
example argues that, “In urban areas, cells are no more than half
a mile in radius, which means a short walk to any venue. In the
countryside, the cells are larger, up to five miles in radius”;
therefore such accuracy may give false location.
GIS
Among many
definitions of GIS, the gis.com definition is ‘Geography is
information about the earth's surface and the objects found on it,
as well as a framework for organizing knowledge. GIS is a technology
that manages, analyses, and disseminates geographic knowledge.’
Simply put,
GIS is a database of the world. So in layman terms, a GIS database
can provide a map and related data such as the road name, building
name etc on any surface on the earth. Therefore if an X, Y is given
to this database, a map related to that X, Y could be generated with
the graphical representation of the X, Y in terms of country,
district, road name etc.
The client device
The client device can be a PDA, Mobile phone, a
notebook laptop etc. This is the device which has the GPS receiver
embedded in it. So this device when carried out can get its GPS
coordinates from the satellites and transmit back this location
information back to the system for further processing.
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