Developer Robert Levine once traveled every 10 days to construction sites across the country, lugging his bags and racking up thousands of frequent flier miles. These days he monitors all of his projects from the comfort of his office, using a computer that continuously receives high-resolution images of the construction sites.

“I’m constantly watching the screen to keep an eye on developments,” Mr. Levine, the president of RAL Companies, said. “Sometimes I pick up my BlackBerry and am on the phone with contractors in a minute.”

The camera system is “a true evolution of the business,” he added.

The use of live Web cameras by New York City and national developers has skyrocketed over the last several years, as air travel after the attacks of September 11, 2001, became more challenging and technology more reliable. Developers now monitor construction projects around the world from small command centers in their high-rise office towers in Manhattan.

Two of the privately held companies that provide the camera systems, EarthCam and OxBlue, said they have contracts with hundreds of developers and construction companies, including Forest City Ratner, Sherwood Group, and Turner Construction Company. EarthCam has been operating since 1996, while OxBlue was started in 2001.

“This is a key technology for a developer in New York that is using an architect in Miami, a design team in Los Angeles, and the project is taking place in Dallas,” the chief executive of EarthCam, Brian Cury, said. “And it’s just getting started in terms of the potential.” The images produced by some of the cameras allow developers to zoom close enough to see a construction worker’s lunch, he said. Mr. Levine said he can pick up his BlackBerry only a few minutes after concrete is poured at his company’s $200 million hotel project in Telluride, Colo., to make a correction.

“It has been even more effective when contractors in the field did not know we had the cameras and would be on the phone telling us something about work we could actually see and take them to task on,” Mr. Levine said. “This has happened with portions of sites that were supposed to have been excavated, equipment supposed to be on site, and concrete being formed or poured.”

One of RAL Companies’ biggest projects is One Brooklyn Bridge Park, a 449-unit residential building in Brooklyn Heights.

The technology also allows developers to create time-lapse films of the total construction on their projects for marketing purposes, as well as to keep lenders and other investors apprised of their progress. Since the images include the time and date, they have become the deciding factor in several legal and contract disputes, developers said.

“It used to be that you’d get an invoice from a crane operator who said he was there on February 1, and you’d have to argue about it,” Mr. Cury said. “Those days are over when you have a camera with a time-date stamp.”

Fisher Development Inc., which has an office in New York, used the cameras during the construction of the Williams-Sonoma Home in Missouri and of a pop-up store in Times Square for the Academy Awards in 2006.

“This industry is using cameras everywhere,” the vice president of marketing and a co-owner of Fisher Development, Sydney Bernier, said. Her company uses OxBlue, which sets up the equipment and maintains it for developers.

“Many more developers are using this now,” Mr. Cury, who said the images are of increasingly higher quality and are available more quickly, said. “And it’s only going to get better.”