As digital technology advances, not just online advertising but also the outdoor advertising industry is reaping the benefits.

Digital out-of-home networks are growing at a rate of about 10 new networks per month, according to a new report from Profitable Channels, MediaPost writes (via MediaBuyerPlanner).

The report, which estimates that about 700 digital out-of-home networks have launched since 2002, says the networks will account for $1.2 billion in national ad spending this year. That, the article points out, gives the medium the strength - at least in terms of ad spending - of a major TV network daypart.

These networks exist in venues such as high-rise elevators, public rest rooms, gas station pumps and stores such as Wal-Mart. The growth has spurred major media buying agencies to develop "shopper media" divisions within their out-of-home operations. Leo Kivijarv, VP of research at PQ Media, says it is one of the smallest segments, but is also one of the fastest growing.

The category now has its own trade association, the Out-of-Home Video Advertising Bureau (OHVAB), which is attempting to bring some structure to the marketplace.