Posts Tagged ‘web application’

Find a Parking Space Online: Street-embedded sensors monitor parking availability

Sunday, July 27th, 2008

Carspotting: Part of a mesh network, this sensor node embedded in a San Francisco street can detect when a car parks in the spot beside it. It also monitors passing traffic. See following image credit to Streetline.

This fall, San Francisco will implement the largest mesh network for monitoring parking to date. Around 6,000 wireless sensors from the San Francisco company Streetline will be fixed alongside as many parking spots, monitoring both parking availability and the volume and speed of passing traffic. The city hopes that displaying information from the sensors on Web maps, smart phones, and signs on the street will reduce the traffic and pollution caused by circling cars.

A mesh network differs from a typical wireless network in that there’s no central transmitter: every node can transmit to every other node. Mesh networks have generally been used for environmental monitoring, or to grant wireless devices Internet access.

When sensor networks have been deployed roadside, it’s usually been to monitor traffic, not parking. In urban areas, traffic-monitoring systems have been used for congestion pricing: during business hours in downtown London, for instance, the license plates of cars are photographed, and the drivers are sent a bill. Some parking garages also have signs that tell drivers where the available spaces are, but such systems generally rely on manual car counting, not sensors.

In San Francisco, however, clusters of plastic-encased, networked sensors are embedded in the surface of the street. The main sensor in the cluster, which is commonly used to detect cars, is a magnetic one, says Jim Reich, the vice president of engineering at Streetline. Magnetic sensors detect when a large metal object locally disrupts Earth’s magnetic field. One challenge with magnetic sensors is avoiding false positives. “We rely on the magnetometer the most, but in order to fix errors, we use other types of sensors [that] give you much higher reliability,” says Reich. He won’t elaborate on the supporting sensors, but he says that the Streetline system has a high ninety percent accuracy in recognizing parked cars. (more…)