ComScore and Rentrak have long been companies that were known largely to wonks, the sort of people who love to sort through reams of data about what kind of audience is tuning into a cable network or web site. Now the two are poised to gain significantly more recognition.

ComScore, which measures consumer web activity, and Rentrak, which monitors set-top box data to determine how consumers are watching television, said Tuesday that they would merge, with Rentrak becoming a subsidiary of  ComScore. The combination could give rise to a strong competitor to Nielsen, which has long been the dominant company providing audience measurement to media companies and the advertisers who support them.

Under terms of the deal, ComScore shareholders would own approximately 66.5% of the combined company, while Rentrak shareholders would own about  33.5%. Each share of Rentrak will be converted into the right to receive 1.15 shares of ComScore. Serge Matta, currently ComScore’s CEO, will lead the combined company. Bill Livek, Rentrak’s current vice chairman and chief executive, will serve as the new company’s executive vice chairman and president.

“What we are going to be creating is a cross-platform currency product” that will help media companies and advertisers find a new way to determine the value of audiences who watch video across traditional TV and new forms of video, said Matta, in a brief interview Tuesday night. The new company intends to unveil more details about that after regulators consider their intend to merge, he said.

The two join forces as more media companies have been vocal about their desire for new ways to measure video consumers who use mobile devices, streaming video and subscription-on-demand services as easily as they do so-called “linear” television. Philippe Dauman, the chief executive of Viacom, which has seen ratings for cable networks like MTV, Nickelodeon and Comedy Central tumble, has made it clear he expects the company to generate significantly more advertising revenue from deals that are not based on Nielsen ratings. Leslie Moonves, chief executive of CBS Corp., has said in recent remarks that Nielsen ratings measuring overnight viewing are of less value to TV networks because they do not count the growing audience that watches TV programs days after their on-air debut.

The two companies were already linked. WPP, the large U.K.-based advertising conglomerate is an investor in both concerns. Martin Sorrell, WPP’s chief executive, told Variety in May that the two measurement companies could be important in an effort to create an alternate system for measuring media consumption

“The world has started migrating to other screens, whether they be tablets or smartphones. There clearly is a change in consumption. In that environment, clients want to know whether they are getting the best out of their investment. The question is what is the best way to do it?” Sorrell said. “What we are going to do is set up this standard — bring the metering and bring the sampling to cover those parts of the media which are not covered or under-covered, and come up with a better mousetrap.”

WPP will own up to 19.9% of the new company, according to Maata and Livek, but will remain a passive investor without a board seat. The two said each of the two companies currently does business with a host of parties that are not part of WPP, and expected to continue to do so. “The ad agencies that we talk with today that aren’t related to WPP are incredibly energized” about the prospect of the combinatoin of the two companies, said Livek, during the interview.

The deal is subject to  approval of shareholders from both companies, and is expected to be completed by early 2016.

Joining together is no guarantee the companies will slow Nielsen’s plans. Devising new measurements for U.S. TV viewers is no easy task, as it requires the agreement of hundreds of advertisers, media-buying agencies, TV networks. Even the choice of technology used to count eyeballs on programs can foment debate.

During a presentation Monday, Nielsen executives said the company intended to have a measurement system in place to count viewers across linear and digital venues by the end of 2015.

“There are myriad analytics options for the media industry, but Nielsen’s focus is on delivering the actual currency ratings data used for trading billions of dollars in advertising,” Nielsen said in a statement. “This requires superior quality, industrial-strength delivery, and gold-standard audited processes and methods.”

The two executives said Nielsen is not on their mind as they consider their company’s future. “When we wake up in the morning, we don’t think about them,” said Livek. “We think about what our customers want and where they are going.”

[Updated, 4:01 PM PT]