Application Of City Digital Traces

APPLICATION OF CITY DIGITAL TRACES
José Manuel Bermejo Ruiz
Madrid - Spain

ABSTRACT
This paper describes a proposal for Madrid City Council presented for the Smart Cities Contest. The system uses a platform for the real-time evaluation of urban dynamics based on the anonymous monitoring of mobile phones. In addition, data are generated based on the instantaneous positioning of buses andtaxis to provide information about urban mobility in real time, ranging from traffic conditions to the movements of pedestrians throughout the city. This system will allow understanding and optimizing urban dynamics, compile information to enhance public services in metropolitan areas and attend much better visitors and foreigners in tourist areas.
KEYWORDS
GPS, real-time control systems,wireless location.
1. INTRODUCTION
Core Engine of the application is a software-only location system that quickly determines device location with 10 to 20 meters accuracy. To quickly and reliably arrive at accurate location results, the database collects raw data from Wi-Fi access points, GPS satellites and cell towers with advanced hybrid positioning algorithms. By leveraging the strengths of morethan one underlying position technology, can provide the best possible location available in any environment.

A mobile device with this application collects raw data from each of the location sources. Then the client sends this data to the Location Server and a single location estimate is returned. The client is optimized so that it communicates with the Location Server only when the locationcannot be determined locally. This behavior minimizes the user's data cost while maximizing battery life.

There are three types of mobile signal sources:

• Wi-Fi positioning performs best where GPS is weakest, in urban areas and indoors.
• GPS provides highly accurate location results in "open sky" environments, like rural areas and on highways. But in urban areas and indoors, tall buildingsand ceilings block GPS' view of satellites, resulting in serious performance deficiencies in time to first fix, accuracy and availability. GPS or A-GPS alone cannot provide fast and accurate location results in all environments. GPS receivers are used inside vehicles and periodically transmit information on a vehicle’s location and speed, together with the associated GPS time, to a centralsystem. These receivers are composed of a control unit and a transmission system, which is based on text messages and/or the transmission of data packets. As a result of communication delays and data packet losses, GPS data need to be carefully processed to extract accurate location data that correspond with the coordinated universal time. If vehicle density within a specific area is quite high, anappropriate processing algorithm in the central system is capable of generating an excellent estimation of automobile traffic.
• Cell tower triangulation provides generalized location results with only 200 - 1000 meter accuracy. It serves as a coverage fallback when neither GPS nor Wi-Fi is available.

This paper is related with a proposal applied for Madrid Smart City Contest 2010 that will takeplace in March 2011. It is performed by José Manuel Bermejo (URJC) and Paula Lema (Telecommunication Engineer).

2. MADGRID - MADRID SMARTCITY

MADGRID allows giving specific answers to the following questions.

• How is the social navigation over the course of the day?
The intensity of mobile phone signal is compared it to the previous day’s data. It is based on a geographic interpolationof the served traffic intensity provided by each monitored antenna.
• How is the pattern of the people during special events?
The application can show the concentration of people during important event thru intensity of mobile phone.
• How Do the Movement Patterns of Buses, Taxis, and Pedestrians Overlap in different areas?
Monitoring of connectivity the software shows the changing...