MacRumors today reports that 4^th generation iphone field test is going on in San Francisco, which is Apple Inc’s head quarters. This conclusion is based on the iBART’s app analytics, which showed an usage record of iPhone identifier 3,1. The current iPhone 3GS hardware identifier is 2,1 and 3G’s is 1,2. The original 2007 iPhone 2G was internally classified by Apple as 1,1.

iPhone developer Pandav has informed MacRumors that they have spotted usage records for an unreleased iPhone in their app’s analytics. The app used was iBART [Free / Paid], a public transportation guide for the San Francisco train system.

PinchMedia provides iPhone applications’ analytics break down by customer usage that includes device’s unique identifier to the developers. Pandav’s app’s November month logs showed up with iPhone3,1 identifier, which clearly would be the new 4^th generation iPhone. Similar kind of logs were found for the iPhone 3GS (iPhone2,1) in October of 2008 about 8 months before it’s release to public.

It’s expected that new iPhone device, with major hardware update, would be announced at WWDC 2010, just like its predecessors.