Google is rolling out four new ad metrics to help clarify the position of the ads displayed in Google search. The new ad metrics are Impression (Absolute Top) % and Impression (Top) % and Search (Abs Top) IS and Search (Top) IS.

The purpose is because the old ad position metric didn’t show where you ad was literally positioned in the search results. Position one did not mean you were at the top of the page, rather just the first ad on the page. So Google came out with new ad metrics to clarify this. Here are the definitions:

Impr. (Absolute Top) % – the percent of your ad impressions that are shown as the very first ad above the organic search results.
Impr. (Top) % – the percent of your ad impressions that are shown anywhere above the organic search results.
Search (Absolute Top) IS – the impressions you’ve received in the absolute top location (the very first ad above the organic search results) divided by the estimated number of impressions you were eligible to receive in the top location.
Search (Top) IS – the impressions you’ve received in the top location (anywhere above the organic search results) compared to the estimated number of impressions you were eligible to receive in the top location.

Here is a visual:

Here is how Google summarized it:

Ginny Marvin has a good summary as well at Search Engine Land.

Forum discussion at Twitter.