-By Mike Shields, Mediaweek

NEW YORK Google has potentially increased its sizable influence over online ad spending by throwing its hat into the increasingly log-jammed world of Internet audience measurement.

The company has launched Google Ad Planner, a free product that promises to allow buyers to identify Web sites that match their desired target audiences -- and ultimately guiding them toward where they should spend their clients' dollars. The new tool puts Google in competition with established industry metrics players Nielsen Online (owned by Adweek and Mediaweek parent the Nielsen Co.) and comScore -- which charge agencies a fee to access their data -- as well as a host of upstarts, including Quantcast, Hitwise and Compete.

According to a post on Google's official AdWords blog, the tool enables buyers to cherry pick individual sites based on their client's specific target demographics and calculate the total audience for an individual media campaign. Buyers have the option of creating a spreadsheet to compile this planning data or exporting it to DoubleClick's MediaVisor tool.

While not mentioning other services by name, Google appears to be positioning Ad Planner as better suited to reporting the audience for smaller, long-tail sites whose audience data may not be as well captured by panel-based services offered by comScore and Nielsen. "If you're a media planner at an ad agency, you know that planning an online display buy can be challenging, particularly in scaling your campaign's reach while keeping it relevant for your target audience," reads Google's blog posting. "Plus, how do you keep track of the millions of sites out there that might be just right for your campaign?"

Nielsen and comScore's services have both taken some hits over the last few years, as publisher complaints over data discrepancies have grown louder, leading the Interactive Advertising Bureau to hammer both companies' methodologies and practices in an open letter issued in April 2007.

Thus, Google's reputation for innovation and data management may make Ad Planner an attractive alternative for buyers. Or, it may be greeted with increased suspicion, as Google, which already dominates search and ad serving, further widens its foothold in the online advertising industry. Advertisers may be wary of providing Google with more details, and particularly more data on their clients' media efforts.

As evidenced by a keynote address delivered by Tim Armstrong, the company's president, advertising and commerce, North America, last March at the American Association of Advertising Agencies' Media Conference, such agency suspicion is prevalent. The title of the speech: "Why Google Is Not Out to Disintermediate Agencies."