On a busy day, nearly 400 large vessels -- ships and tows -- navigate through the port of Houston. Until recently, the US Coast Guard's Vessel Traffic Service had used a system of analog video cameras that were networked and controlled via microwave transmissions to monitor traffic in the channel. This Shell Oil facility in Deer Park, Texas, is one of the many ship and barge terminals under closed-circuit television surveillance by the Vessel Traffic Service, Houston/Galveston. Courtesy of the US Coast Guard.The service encountered several problems with regard to transmission reliability and image quality. After evaluation of several other systems, the Coast Guard in Houston elected to purchase a networked digital-video system from Optivision Inc. The system is based on MPEG-2 technology, which is the same high-quality video compression standard being used for Direct-TV. Numerous advantages"The system we were using wasn't MPEG technology, and it wasn't going down in price," said Lt. Michael Johnston in Norfolk, Va. "We selected Optivision based on a combination of factors, including its cost, reliability and sharper resolution." Here, cost and reliability are closely linked. Part of the savings was in replacement of broken parts that previously had to be custom-manufactured. But Optivision's system also helped reduce costs associated with network downtime caused by the unreliability of microwave transmission of images. Optivision's upgrade replaced cameras at the 10 sites the Guard operates between Galveston and Houston. Monitoring is supported further with 11 video compression units and five decompression units to enable images and programming to be sent via regular telephone lines rather than microwave. Microwave transmissions are especially hindered by storms, when the monitoring of traffic is most critical, pointed out Mike Galli, director of marketing for Optivision. More for less"We're monitoring traffic 24 hours a day, seven days a week. We need gear that's reliable and can stand up over extended use," said Lt. j.g. Tristan Todd in Houston. "We replaced $7000 cameras with $600 units that did the same thing with better resolution," he added. The resolution of the new system, he said, allows staff at the station to zoom in and check a vessel name or pick out a particular ship in congested traffic. Both Todd and Galli said this is a step toward a generation of MPEG technology that will allow the Guard eventually to create a central database of ships to enhance surveillance of US coastal waters. "Once images can be sent to a computer, the Coast Guard can catalog and retrieve pictures of certain ships," said Galli. "They can say, 'Here's a boat we saw in Miami last week that's now in Houston.' Digital imaging facilitates this."