EMarketer is out with its latest mobile forecast revision, projecting U.S. mobile ad revenues to grow from $743 million last year to $4.4 billion in 2015.

This is right in line with the forecast we released in February, especially in the early years. The firm’s 2011 figure of $1.23 billion is particularly close to our $1.19 billion.

When two different sources, models and input methodologies come up with similar final numbers, it’s probably a good sign. It’s also a good sign when they are separated by eight months in what is a fast-paced sector.

Admittedly, eMarketer’s breakdown of ad formats (search, display SMS and video) differs from ours though. You can read more about our methodology and details of the last forecast here.

Our own biannual forecast revision was just completed and should publish next week. The numbers are similar to the last forecast above, with some tweaks based on numbers we’ve collected over the past six months.

These include things like the IAB actuals, and baseline usage inputs from ad networks and market leaders like Google. The complex formula remains the same for the most part, but the inputs differ as more data become available.

More to come next week.