Colorado city switches protocols to keep vehicles on track
When AT&T Wireless Services Inc. dropped its Cellular Digital Packet Data service, the city of Aurora, Colo., faced a tough choice.
Aurora's public works division, which relies on a wireless automated vehicle locator for its fleet of about four dozen vehicles, had to switch to another provider, build its own infrastructure or convert to AT&T's new General Packet Radio Service.
The city chose GPRS. The switch also spurred the city to make better use of data received from the vehicles, via new software from CompassCom Inc. of Centennial, Colo.
Using wireless modems, vehicles automatically report their Global Positioning System coordinates over the commercial wireless network. The whereabouts of street sweepers, de-icing tankers, snowplows and other vehicles appear on the city's geographic information system maps, supplied by ESRI of Redlands, Calif.
Lynne Center, project engineer for the city of 290,000, said the tracking system has been in place since 1998. Aurora decided against building its own network of radio towers. The vehicle locator data could have piggybacked on the public safety voice network, but those airwaves were already near capacity, Center said.
Then AT&T offered to upgrade Aurora to the carrier's Global System for Mobile communications network using the GPRS data protocol. Dominant in Europe and Japan, GSM only recently became available in the United States from carriers such as AT&T and Cingular Wireless LLC.
Support for the city's vehicle locator software was being dropped as well. The vendor, Orbital Sciences Corp., was moving its AVL offering to a hosted Internet service. The city did not want its vehicle location data posted in a public forum.
'We had a feeling there might be some legal issues about who had control and access to the data, so we wanted to maintain control,' Center said.
AT&T Wireless promised the city lower overall cost, and the average 40-Kbps throughput of GPRS is far greater than CDPD's maximum throughput of 19.2 Kbps, said Ritch Blasi, director of media relations for AT&T Wireless.
Aurora's vehicles are getting Sierra Wireless MP 750 GPS rugged wireless modems. The city expects the entire fleet to have GPRS modems by the end of 2004, Center said. And the automatic vehicle location system from CompassCom has a reporting module for trend analysis.
'The reporting module will help us look at some productivity numbers, such as miles per snowstorm or per shift,' Center said. The AVL software will run under Microsoft Windows 2000 Server.