ComScore will merge with Rentrak in an effort to challenge Nielsen in the media measurement market, the companies announced Tuesday.

ComScore measures consumer web activity while Rentrak measures set-top box data. The two combined companies will create a more robust competitor for Nielsen, which is trying to expand beyond its traditional television ratings to a broader suite of products measuring viewership across multiple plartforms.

ComScore CEO Serge Matta will serve as CEO of the new company. Rentrak CEO Bill Livek will serve as executive vice chairman and president. ComScore board chairman Magid Abraham will assume the same role for the new company

Also Read: Nielsen Chief Lynda Clarizio Knows How Many People Are Watching Netflix's Shows, But She Isn't Telling

“With the advent of digital technology, the time has come to offer the cross-platform measurement systems of the future: through which content owners will ultimately be able to quantify their entire audience, and agencies will have access to the cross-platform metrics needed to effectively plan and execute campaigns,” Matta said in a statement.

“This merger also recognizes the critical importance of combining digital and TV assets for next generation media measurement, which requires a higher degree of precision at both a national and local market level,” Matta continued.

Pursuant to the terms of the stock-for-stock merger, which has been approved by the boards of directors of both companies, Rentrak will merge into a wholly-owned subsidiary of comScore, and each share of Rentrak will be converted into the right to receive 1.15 shares of comScore.

Also Read: Nielsen Entertainment SVP: Music's Global Street Date Change Won't Stop Piracy

Upon completion of the merger, comScore shareholders are expected to own approximately 66.5 percent and Rentrak shareholders are expected to own approximately 33.5 percent of the combined company on a fully diluted basis.

In the shifting TV landscape, Nielsen has already been feeling pressure from competitors like Rentrak and comScore. Nielsen president of U.S. media Lynda Clarizio recently told TheWrap that the company welcomes competition, however.

“Rentrak’s biggest challenge is that they don’t have the core television data, which you need as you move to total audience,” Clarizio said, adding of the viewr panels that form the core of Nielsen’s business, “And they don’t have the panels that we do.”

Also Read: Nielsen to Measure Viewership on Roku

“Those panels are a perfect demographic representation of America,” she continued. “I think five years ago, if you were at Nielsen, we would have said we’re only doing panels. We’ve moved beyond that. We know now that we have to bring in all these other data sets. But the panels are a key competitive advantage for us.”

The comScore-Rentrk transaction is subject to shareholder approval of both companies, along with customary regulatory closing conditions, and is expected to be completed by early 2016.