by Terry Smythe Secretary & General Manager Manitoba Taxicab Board Winnipeg, Manitoba, Canada September 1992
INTRODUCTION
On 27 September 1989, Winnipeg taxi driver Paramjit Singh was murdered by David Warriner, later convicted of the crime. It is now known that Mr. Singh was alive for some 15 minutes after he successfully triggered his emergency alarm. His dispatcher, colleagues and police all knew he was in trouble, but nobody could find him. His last known location was at the bus depot in the heart of the city, from where he accepted a trip from David Warriner who directed him to take a certain route out of town, but without a destination. He died beside his taxi.
The circumstances of his situation, seemingly insurmountable at the time, are now being presented with a fine opportunity to summon help most immediate with the help of satellite navigation, otherwise known as (G)lobal (P)ositioning (S)ystem (GPS).
WHAT IS GLOBAL POSITIONING SYSTEM?
For a number of years, the U.S. Department of Defense has been lofting a series of navigation satellites in orbit around the earth, at an altitude of approximately 11,000 miles. When fully deployed, 24 satellites will be on station. 19 are now in orbit, and they are equally spaced in three orbital planes such that at least 3 are in line of sight to a specific location anywhere on the face of the earth.
Each of these satellites continuously transmits a uniquely coded navigation signal. The process is entirely passive. No signal is needed from a ground based receiver to make use of it. This passive approach can therefore accommodate an unlimited number of worldwide users, at no cost to each of the users of the signal.
The GPS black box mounted in the trunk, no bigger than a good book, has the ability to receive these navigation signals from the array of satellites in line of sight and instantaneously calculate its position by triangulation in terms of precise latitude and longitude on the face of the earth. To be useful to the taxi industry, this signal must be transmitted to a base computer, typically riding on the carrier of the vehicle's voice radio. The base computer then takes over by translating the latitude/longitude signal into a specific location on city streets, displaying it as a moving miniature vehicle (icon) on a computer screen.
A single location signal is of limited value, but a stream of these signals flowing into the base computer, provides the ability to track the precise movements of a taxi with a driver at the wheel in fear of his life, following the commands of his assailant in the back seat.
For a number of years, the U.S. Department of Defense has been lofting a series of navigation satellites in orbit around the earth, at an altitude of approximately 11,000 miles. When fully deployed, 24 satellites will be on station. 19 are now in orbit, and they are equally spaced in three orbital planes such that at least 3 are in line of sight to a specific location anywhere on the face of the earth.