Nearly half of national advertisers reported that at least 25 percent of their online marketing budget goes to local targeting. Yet national brands remain confused about how to accurately measure ROI for their local online ad efforts.

That confusion is driving companies to test a hodgepodge of measurement techniques in an effort to find out if in-store sales are being driven by online ads, said Greg Sterling, principal of Sterling Market Intelligence.

"There was a surprisingly large percentage that were doing some sort of geo-targeting, and they were using lots of different traffic sources, different ways of measuring success and different tracking terminologies," said Sterling. "I interpret that to mean they're struggling."

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