Microsoft has bought TV ad targeting company Navic in a move to build out an ad platform that extends across all media. Terms of the deal were not disclosed. Navic creates interactive TV ads and, through its Admira network, works with cable companies to deliver ads targeted to specific audiences. Navic says its technology runs on roughly 35 million TV set-top boxes.

Navic is the latest in a string of acquisitions that augments and expands the company’s ad targeting capabilities. In 2006, Microsoft acquired video game ad network Massive, and in 2007 it acquired mobile ad network Screentronic.

The Navic purchase sets up a new front in the Microsoft / Google war. Google is trying to get its own TV ad buying service off the ground, though its service is only through satellite company DISH Networks right now. But Microsoft faces other competition in the race to make TV ads more targeted and trackable like web ads. Spot Runner offers ad targeting services and recently raised $51 million, and the cable companies are banding together to create their own ad network, dubbed Canoe Ventures.