Social Networking

Applications
Title	Social Networking
Author(s)	Rui Barradas Pereira.
Level	Basic
Year of Publication	2011

Social Networking as become a part of our daily life and millions of user use social network to interact with its social and professional contacts. The concept of posting information about "what are you doing" very rapidly progressed to post "where are you".

Location enabled Social Networking allows you to post your current location or to check into places or venues. This allows the user's friends to know where the user is and the user can know what other user are at the same location where he is.

Application Architecture

Social Network applications depend normally on an architecture that includes a user mobile device and an information server accessible through the internet.

The user mobile device is usually a mobile phone with internet access, localization capabilities and a multimedia interface running the social networking application.

There are two types of operation for these applications:

• The application periodically sends automatically the user position to a server. The user's location is available to its friends in the social network.
• The user posts its position by posting its coordinates or by checking in nearby locations or venues. The user location is available to its friends and the list of other users present at the location is available to the user.

Variants to this architecture are:

• The more basic pedestrian navigation applications support only outdoor pedonal movements not supporting public transportation.
• These applications can be combined with Location based Information Streams to provide additional information to the user.

These applications are considered non-critical applications.

The precision required by these applications is medium. The current accuracy provided by civilian GPS enough in most situations but not in all since pedestrian are more often in situations with less visible satellites. To support indoor navigation these applications would need a much higher availability than normally given by civilian GPS that might require the use of inertial sensors or other indoor localization techniques.

Application Characterization

Pedestrian Navigation as been wrongly seen as a mode of Road Navigation. But the fact is that the environments where pedestrians move around are generally more difficult than the road environment. Pedestrians normally move in sidewalks where the buildings shadow the GNSS signals, in tree shadowed environments and in indoor three-dimensional environments.

At present, satellite navigation based on GNSS and without the use of inertial systems, is not accurate enough to guide pedestrians, especially around cities. When few satellites are in view because of tall buildings, positioning accuracy can be little better than 30 to 40 m. Satellite based augmentation systems (EGNOS, WAAS), however, improves the accuracy of GNSS positions to a few meters, making it sensitive enough to locate obstacles in the street.

These environments are much more difficult than Road Navigation that even in urban environments will have better satellite visibility. To support indoor navigation these application would have to support inertial sensors integration or other indoor navigation techniques.

In simplified pedestrian applications the maps used for road navigation can be reused but this limits the degree of functionality that the application can provide. Pedestrians move in the sidewalks, not in the roads and can move more freely in the environment since they can use pedestrian streets or pathways and go across open areas.

The mapping of indoor environments is also much more complex and dynamic requiring tridimensional mapping that is not generally required for road applications.

Also to support public transportation, the routes and the frequency or the timetable of the public transports must be supported making the database and the routing algorithms more complex.

Currently the interface for these applications is supported by the graphical and audio interfaces of mobile phone but these applications would benefit significantly from the used of augmented reality technologies.

Application Examples

Applications and services that fit in this category are:

• Journey Pro by Navitime: Journey is pedestrian navigation application for iPhone and Android.
• Ovi Maps: Nokia free navigation solution that supports pedestrian navigation in the Walk mode.
• Google Maps: Google free map solution that supports pedestrian navigation including public transportation.
• Personal Navigation Devices: Most road oriented personal navigations devices support pedestrian modes although usually the same maps and routing algorithms as for road navigation are used.