quantcastQuantcast, an analytics firm specializing in data about how to expand audiences for digital advertising, has just landed a $27.5 million round of capital led by Cisco Systems and Polaris Venture Partners. Based in San Francisco, it says it will use the money to build out its Quantcast Media Program, a marketplace to buy and sell advertising space based on real-time measurement.

The move is interesting for Cisco, which has taken a greater interest in online content and advertising delivery as of late. It already works closely with consumer electronics makers, IP service providers and content publishers. Quantcast’s technology could help it expand its offerings for all of these customers, allowing them to deliver ads tailored to specific audiences.

It’s not enough to gauge impressions garnered by internet ads. The measurement tools of the future will need to be able to collect data from and personalize content for digital television, set-top box programming, mobile phones and more. And Cisco wants to be at the forefront of this shift.

Quantcast grew steadily in 2009. Last April, it launched a new service called Quantcast Marketer, which slices and dices impressions data to give advertisers an in-depth look at how consumers are interacting with their brands. The idea is to give them the intelligence they need to better plan and buy advertising campaigns.

Instead of just providing how many people viewed a campaign, when and where, Quantcast uses the data it gathers to build elaborate profiles of audiences, detailing their interests and how they are best reached by marketing. This distinguishes it from many of the other marketing and measurement firms in the field.

So far, its unique services have garnered an impressive clientele. It has worked with NBC Universal, Time Inc., Hulu, CBS, Fox, ABC and Bloomberg, among many others, to collect audience data for some of the biggest properties on the web. It also counts ten of the most prominent online media advertising agencies among its top users.

Founders Fund and Revolution Ventures also contributed to the recent round of funding. Quantcast has now raised $53.2 million to date.