That’s how much area it would take to lay out all 900,000 of the digital signs expected in the market by the end of 2009 if each were a 40-inch display.

“That’s 6.3 million square feet of dynamic digital display area,” marveled Dale Smith, senior director of business development at Peerless Industries Inc.

Size isn’t the only thing that matters, however, among a number of factors fueling the growth of the networks. Proof-of-performance has improved dramatically, more ad space is available to sell, planning and placing the ad content has never been easier, and an increasing number and diversity of media-buying divisions are writing checks, taking money from pockets typically emptied into TV and Internet buys.

Proof of the boom: the Out-of-home Video Advertising Bureau, whose members include many of the largest DOOH networks, reports that video advertising networks are a $1.01 billion industry now and growing at 25.4 percent annually. The Bureau predicts the industry will be at $3.2 billion before 2012.

Buyers, sellers tuning in

NBC, ABC and CBS have been promoting DOOH ad placement to their advertising clients, often bundled with TV network proposals. Cable system and billboard ad sales organizations have been ramping up their efforts, and print media is expected to engage DOOH ad sales as a way of leveraging their sales organizations.

But some media buyers and planners are looking for a different way. Brand managers, agencies, creative houses and others have become frustrated with the high amount of effort it takes to place ad campaigns that take fullest advantage of the medium. Here, network operators have an opportunity to capitalize on the sharpening of their own marketing kits, proposals and analytics.

“A fact of modern life and commerce is that better approaches will be used,” said Shelley Palmer, media guru and author of the best-seller “Television Disrupted,” when addressing a packed house at the NEC Digital Solutions Summit in late August. “Digital out-of-home is powerful because of its placement at point-of-event such as purchase, decision or attention. As an addressable media, it exploits the digital communications supply chain to provide better message targeting capability – the holy grail of the advertising.”

DOOH network account execs easily could fill a media buyer’s calendar, and ad placement is becoming increasingly easy. Industry associations such as OVAB and www.OOHDigital.ca offer direction to many networks.

And DOOH ad sales agencies such as Adcentricity, SeeSaw Networks, Charter Media and MediaPlace offer convenience to media planners and buyers. New entrants to this service area such as rVue, UnSoldSpace.com and AdSemble suggest that the administration in using DOOH for advertising will become more streamlined.

Not only are placement options becoming more sophisticated, so is the understanding of the medium’s potential. Rocky Gunderson, vice president of SeeSaw Networks, said he is seeing companies using DOOH in ways more sophisticated than ever before, and believes the model is moving beyond place-based advertising into more strategic communications.

“That’s really exciting, particularly when from a creative perspective you see how effectively digital-signage can deliver a relevant, timely message,” he said. “When you add to that the explosive growth in digital-signage companies, increasing the venue choices brands have to advertise in, this media now has the reach of TV with the target-ability of the Internet. Planning teams are beginning to stand up and take notice.”

Rob Gorrie, president of Adcentricity, agrees.

“Today there’s a better understanding of the digital OOH medium, and folks are more comfortable with how to use it,” said. “This is what’s driving demand for digital OOH. And it’s about time.”

Lyle Bunn is a commentator, contributor and consultant to North America’s DOOH industry.