ABSTRACT
Location Based Advertising aims at delivering location-specific advertisements to be displayed in public transportation including buses, metros & cabs. The advertisers can reach their targeted audience easily and the users can find what they’re looking for wherever they are. GPS technology allows us to find the location and our system exploits this information to display advertisements of shops or services in that location. The advertisements change with the location and the user can get down at a particular location on finding an interesting advertisement.
PROJECT DESCRIPTION
The LBA system gets the location of the public transport system(from the GPS using the RS232 serial communication protocol), maps the location to the advertisements for that location(using a program) and finally display this content at the output(Dot Matrix Display) on the public transport.
To achieve the required functionality, we need to set up the following:
HARDWARE
GPS Module – Gives information in the NMEA format
The 8051 Microcontroller – Programmed to do everything between getting the location and showing the ads. Additional memory(64K) may be needed.
Dot Matrix Display – The output device – The best suited for our needs.
RS232 Interface for serial communication – Needs a MAX232 (converts the RS-232 signal voltage levels to TTL logic) & a DB9 connector.
SOFTWARE
We are making a software (in Embedded C) that gets data from the GPS and converts it into information we can use – which is a specific location. It then maps that location to the ads to show for that location. Displays this onto the output based on arguments decided by the program.
We intend to use Keil C and Flash Magic to write the code and to program the 8051 with it. The 8051, once programed with the code, needs to be interfaced with the GPS at the input and with the dot matrix display at the output.
The protocols and technologies involved are as follows:
GPS(Global Positioning System)
The system is actually a constellation of 27 Earth-orbiting satellites that circle the globe at about 12,000 miles (19,300 km), making two complete rotations each day. The orbits are arranged so that at any time, anywhere on Earth, there are at least four satellites “visible” in the sky. A GPS receiver’s job is to locate four or more of these satellites, figure out the distance to each, and use this information to deduce its own location. This operation is based on a simple mathematical principle called trilateration.
Suppose we know that a person is 10 kms from a satellite A in the sky, he could be anywhere on the surface of a huge, imaginary sphere with a 10-km radius. If we also knows that he is 15 kms from satellite B, he is somewhere on the overlap of the first sphere with another, larger sphere. The spheres intersect in a perfect circle. If we further know the distance to a third satellite, we gets a third sphere, which intersects with this circle at two points.The Earth itself can act as a fourth sphere and only one of the two possible points will actually be on the surface of the planet, so we can eliminate the one in space. We then knows his current location.
NMEA 0183
The National Marine Electronics Association (NMEA) has developed a specification that defines the interface between various electronic equipment.
GPS receiver communication is defined within this specification. Our program will understand data in NMEA format. This data includes the complete PVT (position, velocity, time) solution computed by the GPS receiver.
The idea of NMEA is to send a line of data called a NMEA sentence that is totally self contained and independent from other sentences. There are standard sentences for each device category. All of the standard sentences have a two letter prefix that defines the device that uses that sentence type. (For gps receivers the prefix is GP) which is followed by a three letter sequence that defines the sentence contents.
For instance, An NMEA sentence beginning with $GPGLL gives the Geographic Position, Latitude/Longitude and time.
We can then use the information about the position in our program to map the position to a particular location.
RS-232
The RS-232 is a popular communications protocol for connecting computers to modems and varied peripherals. The GPS module communicates with application system via RS232 (TTL level) with NMEA 0183 protocol.
Communication as defined in the RS232 standard is an asynchronous serial communication method. The word serial means, that the information is sent one bit at a time. And the word Asynchronous tells us that the information is not sent in predefined time slots. Data bits are sent with a predefined frequency called the baud rate. Both the transmitter and receiver must be programmed to use the same bit frequency for communication.
Dot Matrix Display
A Dot Matrix Display is a kind of an LED display with the LEDs arranged in a rectangular configuration in the form of a matrix. It is used to display information on machines, clocks, railway departure indicators and many other devices requiring a simple display device of limited resolution.
REFERENCES
BOOKS
[1] Muhammad Ali Mazidi, Rolin Mckinlay, Janice Gillispie Mazidi, “The 8051 Microcontroller And Embedded Systems Using Assembly And C”: Pearson, 2007.
ARTICLES
[2] Dr. Dennis D. McCrady. “The GPS Burst Detector W-Sensor”. Sandia National Laboratories.
[3] Daly, P.. “Navstar GPS and GLONASS: global satellite navigation systems”. IEEE.
[4] EIA standard RS-232-C: Interface between Data Terminal Equipment and Data Communication Equipment Employing Serial Binary Data Interchange. Washington: Electronic Industries Association. Engineering Dept. 1969.
MANUALS
[5] NXP P89V51RD2 datasheet
[6] LD-4W GPS Module Manual
INTERNET
[7] http://aprs.gids.nl/nmea/ – “GPS – NMEA sentence information”
[8] http://national.com/an/AN/AN-350.pdf – “Dot Matrix Display Interface”