Google on Wednesday showed off new features of its digital maps ahead of Apple's annual developer conference next week, where Apple is expected to roll out its own mapping service as a default on its devices.

Google plans to model the world in 3D, by adding 3D models to entire metropolitan areas to Google Earth on mobile devices. This is possible thanks to a combination of the company's new imagery rendering techniques and computer vision that let Google automatically create 3D cityscapes, complete with buildings, terrain and even landscaping, from 45-degree aerial imagery.

By the end of the year Google aims to have 3D coverage for metropolitan areas with a combined population of 300 million people.

Google will be also deploying a fleet of small, camera-equipped airplanes above several cities in order to shoot 3D pictures. The company declined to name the cities, but it showed a demonstration of a 3D map of San Francisco, in which a user can navigate around an aerial view of the city.

Google also announced that in the next few weeks it's debuting offline maps to Android phones. By preloading maps to mobile devices, users will be able to navigate to places without a data connection and without a paper map.

Apple is expected to announce its own mapping service at the company's annual developer conference. That could deal a significant blow to Google, since currently more than 90% of U.S. iPhone users use Google Maps.

Google's Street View is also getting an update. Luc Vincent, Google's Street View engineering director said that Street View cameras will be going off-road to capture images. The cameras are backpack-sized and can wornd by users and capture 360-degree images anyplace they can hike.