Google (GOOG) today unveiled a new tool that promises to measure Internet usage more precisely. Called AdPlanner, it combines search engine and audience measurement data to create a richer, more intelligent picture of Internet usage, one that may prove far more useful to advertisers looking to identify the best places to buy ads that will reach their target audiences. Slap it together with the recently announced Google Trends for Web Sites and what use is there for traditional advertising-research suppliers?

Great news for media buyers and advertisers who’ve long relied on comScore (SCOR) and Nielsen/Netratings and their shallow, inconsistent metrics. Ugly news for comScore and Nielsen/Netratings, which now seem destined to be disintermediated by Google in much the same way the company disintermediated the rest of the online advertising industry. Sadly, they’ve no one to blame for this but themselves. It’s not like they haven’t been hearing complaints about discrepancies in audience measurement for nearly a decade now (some, presumably, from Google itself).

“We in the marketing-media ecosystem have spent too many years trying to clean up the residue of flawed media-research methodologies,” Randall Rothenberg, president & CEO of the Interactive Advertising Bureau wrote in a scathing letter to comScore and Nielsen//NetRatings back in 2007. “We simply cannot let the Internet, the most accountable medium ever invented, fall into the same bad customs that have hindered older media and angered advertisers for decades–customs such as inadequate samples, accepted out of begrudging convenience; or phantom metrics, like ‘pass-along readers,’ that add shadowy bulk to audiences that cannot be measured directly; or metering technologies and processes that are easy to game.”

Why the sudden change? The increasing popularity of AJAX (Asynchronous JavaScript and XML), which allows a Web site to refresh content without reloading an entire page, demanded it. “It is not that page views are irrelevant now, but they are a less accurate gauge of total site traffic and engagement,” said Scott Ross, director of product marketing at Nielsen/NetRatings. “Total minutes is the most accurate gauge to compare between two sites. If [Web] 1.0 is full-page refreshes for content, Web 2.0 is, ‘How do I minimize page views and deliver content more seamlessly?’ “

Yeah, that or how do I inflate my page views and capitalize on the resulting publicity.

Anyway … one possible result of Nielsen’s adoption of time onsite as its primary metric of audience measurement will be a decline in rank for Google. After all, no one really spends much time on the site. We visit, conduct our search, and then we’re off. That said, the company could probably care less about such things. If Google has taught us anything, it’s that the most meaningful metric for success on the Web is not page views, but profitability.