Apple and its iPhone operating system may still dominate the smartphone ad space market but Google is fast gaining ground, according to a survey by Millennial Media, an independent ad network.

Millennial Media reports that Google and its Android OS matched Apple’s iOS in smartphone ad space in October. Both popular operating systems had 37 percent shares of the smartphone ad space market whereas back in June, Apple dominated with a 56 percent share compared with Android’s 17 percent.

Android’s gain comes at a cost to Research In Motion, whose BlackBerry only had a 20 percent share in October. Nokia, which dominates the international market with Symbian, had only a two percent share in the USA, as did Microsoft.

Yet despite Google’s encroachment on Apple’s market share, Millennial found that the iPad tablet is making inroads in mobile advertising, growing more than 100 percent in October over September. In the meantime, Motorola has been enhancing its image thanks to Android, and is now the No. 3 phone maker, as Droid 2 and Droid X are now in the Top 30 of mobile devices. RIM had six of the Top 30 devices.

Google’s ad space success should come as no surprise. The Android OS is now officially the second most popular operating system in the world, according to a recent report by the research firm Gartner. In fact, Google's mobile platform now accounts for a whopping 25.5 percent of the worldwide smartphone market, up from only 3.5 percent in the same quarter last year.

Symbian still remains the most utilized operating system in the world with 36.6 percent of the market; although that is down 10 full percentage points from the third quarter of 2009. Apple's iOS and Research in Motion's Blackberry platform finished third and fourth respectively, accounting for 16.7 percent and 14.8 percent of all smartphone purchases.

Meanwhile, Microsoft's Windows Mobile operating system plummeted from 7.9 percent to 2.1 percent of the market over the last year.

Edited by Tammy Wolf