Minneapolis officially launched its travlink "Magic Bus" advanced traveler information system to provide commuters with real time information on arrival times of GPS equipped buses.
Georesearch Inc., (Vienna, Virgina) wants to use its new generation of technology incorporating GPS hardware to expand into real time vehicle tracking and fleet management markets, including emergency 911 and military command and control.
LaSalle Ambulance Service in Buffalo, New York teamed GPS with desktop mapping software to track and monitor its fleet of 42 ambulances and three aircraft. As a result, LaSalle's vehicles have logged response times of less than eight minutes for 96-98 percent of its emergencies.
These are some of the notable points referring to the impact that he GPS technology has made on the Vehicle tracking industry. With the kind of advantages, features and pricing of the GPS modules available today, a sluggish industry is awakening with full vigour to flood the market with reliable, low cost, compact and multi-featured equipment. The requirement in India is no less compared to the situation abroad.
This paper provides a brief overview of a tracking system developed by Advanced Micronic Devices Ltd. using GPS and GIS to track any dynamic platform.
AMDL has developed the GPs based tracking system with 50% financial contribution from Department of Electronics (DOE), under the FANS Program. DPTIS is a general purpose system that can be easily customised for a wide range of applications such as airport vehicle monitoring, cargo vehicle monitoring, ocean vessels monitoring etc.
DPTIS Principle
Dynamic Platform Tracking and Information System (DPTIS) employs and combines well suited technologies for positioning, mobile communication and geographical information to bring out a flexible surveillance of mobile units on ground, water and in air, The basic function is the tracking of all mobile units on ground, water and in air. The basic function is the tracking of all mobile unit and the control center.
Exact positioning of mobile units is obtained by using Differential Global Positioning System, to an accuracy of better than 10m.
The Positioning Element
Global Positioning System (GPS) is a satellite based, all weather, worldwide precise positioning system. It basically consists of 3 segments.
The Space segment which comprises of a constellation of specific GPS satellites launched in specific orbits with orbital periods of 12 hours.
The Control segment consists of the master control station at Colorado springs along with few other stations positioned around the globe to monitor and maintain the health and orbits of the GPS satellites.
User segment Consists of the military and the commercial users who use the GPS receivers to track signals from GPS satellites and use the triangulation technique to find out their positon on the surface of the earth. A standalone GPS receiver is capable of giving accuracies of about 100m RMS.
An upgradation of the GPS is Differential GPS (DGPS) which is capable of giving acuracies better than 10m. For this a special GPS reciever known as the reference receiver is placed in a known presurveyed location and by tracking the GPS satellites is able to compute the errors in the system. Using wireless communication links the error corrections are transmitted to the mobile GPS receiver s to enable them to apply these corrections in their algorithms and enhance their position accuracy.
- DPTIS components
- The system basically consists of 2 principal elements
IN-Vehicle unit (IVU): The IVU consists of the GPS receiver, a control Display Unit (CDU) and a communication system.
Control Centre The control centre consists of high a high end PC optionally in a network environment along with the communication system and a
The communication link is a two way wireless link that caters to data exchange between the control centre and the vehicles.
In-Vehicle unit (IVU): The GPS receiver used in the vehicle will have 8 or more tracking channels with parallel satellite tracking capability. Research continues to show that such receivers provide the ideal coverage for maximum GPS performance.
The "urban canyon" creates a special problem for the automotive application. Large buildings and structures made of concrete, steel and glass from canyon-like walls which interfere with incoming signals transmitted from GPS satellites. GPS receivers operating in these heavily-structured areas are subject to signal interruption and the multipath effects of signal reflection. The degree to which a GPS receiver is able to handle these anomalies is a strong function of the receiver's signal tracking strategy. Additional channels allow the receiver to continuously track more visible satellites, which increases overall performance and reliability.
For application which require a high update rate and operate in a hostile "urban canyon" environment it becomes necessary to add a dead reckoning sensor to IVU. This will consists of a self contained heading sensor and a speed sensor to sustain the position updates during GPS outages until such a time that GPS comes back online.
The CDU serves as a link between the GPs, the user in the vehicle and the communication system. Its functionallity includes obtaining and storing the currrent position fixes computed by the GPS receiver for eventual commanded or regular interval transfer back to the control centre. Data messages originating from the control centre are displayed on an LCD screen and if required the CDU will also generate Audio-visual alarms to attract the attention of the operator. The CDU will also allow the user in the vehicle to select and convey messages back to the control centre. Entry keys are designed depending on the type of application. The options can be to have just browse and select keys or full fledged alphanumeric keys allow access to these messages and the browse and select keys allow the required message to be picked up from the available ones for transmission back to the control centre. On the other hand alphanumeric keys allow freeform entry of messages.