(AP) -- Two of the largest companies involved in tracking and analyzing Web traffic are joining forces to measure digital audiences more comprehensively.

The partnership involves comScore Inc. and Omniture Inc., which announced Tuesday that it agreed to a $1.8 billion takeover by Inc.

ComScore and Omniture plan to announce Monday they are launching a unified digital audience measurement system. It will combine Omniture's method of analyzing by looking at data collected by Web servers with comScore's estimates of what's happening across the Web using panels of Internet users recruited for the task.

This, the companies say, will give Web sites and advertisers a single source for measuring how many visitors they attract, how often and who those visitors are.

The two companies often came up with different sets of numbers because they had disparate goals and used different ways of collecting data.

Omniture CEO and co-founder Josh James said operators sometimes would read a report on their traffic going down, even as their own server data showed an increase.

The two companies hope to address that by giving creators and advertisers a consistent set of numbers.

By joining forces, Omniture and comScore could also shed new insights into digital audiences. For example, comScore's panel may not fully represent the proportion of Macintosh users out there, and those users tend to visit video Web sites at a higher frequency than their PC counterparts, comScore CEO Magid Abraham said. Omniture's server-based data collection could track a visit regardless of the computer or device used.

Omniture, meanwhile, doesn't have demographic data on the users visiting, and it couldn't tell that the same person visited both Facebook and MySpace, for instance. That's where comes in.

James said the timing of the announcement near the Adobe acquisition was just a coincidence. The deal, which is expected to close by November, will combine Omniture's services for figuring how to best deliver messages and Internet advertisements with Adobe's tools for creating these Web sites and ads.

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