NEW YORK: Nielsen is to change the way it measures ad reach and frequency across media by combining its TV and online metrics into a single score.

The new system will measure "cross-platform campaign ratings" by merging the research firm's principal systems of measurement for both media. This follows Nielsen's launch of its standalone online rating in August 2011.

Global media agency GroupM will be the first company to use the system.

Cross-platform campaign ratings are designed to improve ad effectiveness measurement for advertisers who launch integrated campaigns across online and TV. It could also assist these firms in allocating budgets more accurately across media.

Speaking to the New York Times, Steve Hasker, president for media products and advertiser solutions at Nielsen, said: "This measure will show you the reach of your campaign on TV, the reach of your campaign online, and will show you the overlap between the two." 

Rino Scanzoni, GroupM's chief investment officer, added: "Our advertiser clients increasingly recognize that traditional television advertising and online video advertising must work together.

"It's vital that we have consistent measurement."

Since launch, Nielsen's online ad ratings system has gained traction among advertisers. Hasker told the New York Times that the ratings have been used to measure around 600 campaigns so far.

Last month, FMCG giant Unilever also announced that it would use the online ratings for all of its US digital campaigns going forward.

Data sourced from New York Times/Nielsen; additional content by Warc staff