Best practices for tracking page depth metrics such as pageviews on infinite scroll website [on hold]

I have an infinite scroll website where a user can scroll very deep into content archives. Essentially they could scroll 50 pages if they wanted to.

Initially when I created the site I tracked "pageviews" on both the initial site load, but then each time a user scrolled down and loaded more content, a virtual pageview was triggered.

One of the problems here is that in some cases the amount of items loaded is less than other cases. For example, mobile pages load less content for the sake of bandwidth, and desktop pages load more content.

Because of this, the actual "page" size is not the same and a mobile site could trigger more pageviews... what I'm saying is that it doesn't give a great baseline metric across the site.

Pageviews are important because I run CPM based ads that rely on knowing how much traffic is available to be sold. Pinterest is a lot like my website so it makes me wonder how they go about tracking the infinite scroll feeds.

Is there a better way to track virtual scroll pageviews? Perhaps using a depth metric instead or measuring the height of the browser and using that height as 100%, then as a user scrolls, incrementing the percentage?

Document height = 600px => set baseline as 100%
User scrolls down 300px more, now scroll is at 150%

This is just one thought, but I'm open to others. Any ideas?