• by Mark Walsh  @markfwal, March 13, 2012

Even before the release of the new iPad, Apple’s iOS managed to surge further ahead of Android as the top platform on at least one mobile ad network in February. New data from InMobi shows iOS’ share of ad impressions increased from 28.1% in November to 35.2% last month, while Android slipped from 34.5% to 30.9%.  

The Google platform also dropped from a 32.7% share in January, while iOS held at the same level from the prior month.

The figures reflect market share on InMobi’s ad network covering North America, reaching a mobile audience of about 57 million.

The company attributed iOS' expansion, in part, to growing tablet adoption, which disproportionately benefits Apple, since the iPad is easily the bestselling device in the category. The company sold a record 15 million iPads in the last quarter of 2011. 

Apple overall had the top three devices on the InMobi network in February, with the iPhone 4 accounting for 10.9% of impressions, the iPod, 6% and the first-generation iPad just behind, at 5.7%. The ad network expects the release of the third-generation iPad on Friday, along with the price reduction of the iPad 2 from $499 to $399, to further propel iOS’ growth.

Pre-orders of the upgraded iPad have already sold out. The latest version features a faster processor, a sharper display, and 4G wireless capability. Gartner estimates iPad sales will increase from 47 million to 69 million this year and that overall tablet sales will grow from 63.6 million to 103.5 million worldwide.

A new survey from ChangeWave Research suggests the iPad will also get a boost from the corporate market in 2012. It found more than one in five companies plan to buy tablets for their employees in the second quarter, and 84% say they’ll buy iPads.

Android is also likely to broaden its tablet presence through sales of Amazon’s Kindle Fire, which runs a version of the Google platform and has quickly established itself as the No. 2 contender behind the iPad. When it comes to handsets, Android is now the dominant player, used by nearly half (48.6%) of U.S. smartphone subscribers, compared to 29.5% for the iPhone in January, according to comScore.

That difference is reflected in recent data from Millennial Media, showing that Android accounted for 47% of impressions on the ad network versus 33% for iOS. Millennial’s network reaches about 100 million unique users in the U.S. -- almost double the reach of InMobi’s.

Research in Motion’s BlackBerry OS is losing ground to iOS and Android on both ad networks. It had a 13.1% share of impressions on the InMobi network in February, down from 17.2% in November. RIM’s failure to crack the tablet market with its PlayBook device launched last year hasn’t helped offset its shrinking share in the smartphone market. 

InMobi said impressions on its network overall have grown 58% in the last three months.