Apple's big announcement in San Francisco, where the company is expected to reveal the iPhone 5 and a number of other surprises, is less than one day away. Alongside Wednesday's announcement of Apple's next-generation smartphone, a possible iPad Mini and a refreshed line-up of iPods, Apple is also expected to release date for iOS 6, the newest version of the company's mobile operating system.

Apple's iOS 6 was unveiled during the Cupertino, Calif.-based company's Worldwide Developer's Conference in in June, and a release date for the OS is expected to be announced with the iPhone 5. Upon launch, iOS 6 will be a free download compatible with iPhone 3GS, iPhone 4, iPhone 4S and iPod Touch devices. The update will also come to iPad 2 and the new Retina Display iPad as well.

iOS 5 brought new features to the mobile platform such as Twitter integration, camera access from the Lock Screen, wireless syncing, a Notification Center, and more. Apple is expected to bring even more innovations and improvements to its newest iOS, and below is a recap of the six top features to launch with iOS 6.

1. Apple Maps. Ever since Apple announced that it will not be integrating Google Maps into iOS 6, users have wondered how the Apple-branded alternative would pan out. The upcoming navigation app will come with turn-by-turn navigation for both drivers and walkers, and will implement vector graphics to add a more lifelike feel to the digitized version of one's town. However, one aspect that could give Apple Maps a boost over Google Maps, and that the integration of third party apps. Apple no longer has its exclusivity contract with Google, meaning that the company will be drawing from places such as GPS and map provider TomTom. According to Apple Insider, Siri will be available to guide users to their destination once a given route is selected, and users can toggle between 2D and 3D views.

2. Passbook. This upcoming feature is designed to act as a digital wallet that owners of iOS devices can use to organize their shopping loyalty cards, coupons, tickets and other printed materials. It was recently announced that two major U.S. airlines, Delta and American Airlines, are on board with Apple for new iOS 6 app, as PCMag reported. This would open up possibilities for users, such as connecting a flight directly to Passbook. This would enable a user's iPhone to bring up a boarding pass on the lock screen once the device realizes that a user is in the airport.

3. iCloud Tabs in Safari.  Many people use their smartphones to surf the Web while on the go, and Apple looks to make the task of tying the desktop and mobile experience together and making it easier and more convenient in iOS 6. When using Safari in iOS 6, links to pages that users have already opened on other iOS devices will appear from a dropdown menu, which will allow users to pick up their browsing exactly where they left off.

4. Better Facebook Integration. Users will now have more ways to share content to Facebook without having to launch the app. Owners of iOS devices can upload from Photos, Safari, Maps, the App Store, iTunes and the Game Center. When iOS 5 rolled out Apple made this same move with Twitter, enabling users to send tweets directly from Safari, Photos, Camera, YouTube or Maps.

5. Panorama Photo Mode. On Tuesday, iOS developer Will Strafach posted on Twitter that the iPhone 5 and iPod Touch will feature a new panorama photo mode, according to MacRumors. This would enable users to capture multiple photos that can automatically be stitched together to form a single panoramic image. The developer has deleted his tweet, saying that the information was already known. He did not say that the Twitter post was taken down due to inaccuracies, but fans will have to wait until tomorrow to see if Apple truly unveils this feature.

6. Siri Improvements. Siri was the flagship feature to come with the iPhone 4S one year ago, and it only makes sense that Apple's digital voice assistant will see a major refresh one year later. With iOS 6, Siri will be able to retrieve sports scores, stats, rosters, game schedules and more. Other features such as OpenTable reservations and move listings per theater will also be available, and Siri will now be available on the iPad with iOS 6. When Siri initially rolled out on the iPhone 4S, users complained of connectivity issues and bugs, with users complaining that the voice activated assistant was not able to understand their requests. Now, a year later, users are likely to see a smoother more enhanced Siri with fixed bugs and glitches.

Apple has not officially announced the release date for its iOS 6 operating system beyond a launch window in the fall. It is likely that the next-generation software will debut with the upcoming iPhone 5, which is rumored to be available for purchase on Sept. 12. Last year iOS 5 arrived on Oct. 12, the same day the iPhone 4S rolled out. Apple is likely to announce the release date of iOS 6 at its press event on Wednesday along with the news on the iPhone 5, iPad Mini and new iPod Touch.