Google's Maps team has made fantastic advances in surveying and mapping seemingly every square inch of navigable ground on the planet. But for mobile users, those maps have always stopped just short of indoor spaces – until now.

Google Maps 6.0 for Android launched Tuesday with a bold initiative: indoor mapping. Partnering at launch with a selection of businesses and public service structures, the new mobile Maps version allows users to see the entire layout of a mapped building, switch between floor plans if the structure has multiple levels, and locate indoor points of interest like retail stores, bathrooms and ATMs.

Obviously, indoor mapping is only useful when the building you're navigating is big enough to warrant it. To this end, Google has partnered with more than 25 major businesses that handle large crowds on a regular basis – major travel sites like San Francisco International and Chicago's O'Hare airports, as well as giant retailers like Macy's and Bloomingdale's.

Considering the layers of thick concrete and steel holding up some of these buildings, it's been difficult for Google to get its location-aware technology up to snuff. "GPS is unreliable and doesn’t work well indoors," said Maps project manager Steve Lee in an interview. "We used similar information to how we've implemented the navigation 'blue dot' feature in the past, and we’ve been able to improve the accuracy indoors, at an accuracy of about 5 to 10 meters."

While half of the initiative begins in U.S. structures, Google is simultaneously launching in Japan, covering Tokyo's massive underground subway network and retail shopping centers (an area where new visitors definitely need a map). While version 6.0 isn't covering U.S. transit, Lee says the Japanese transit coverage "can give us a sense for what's in store for the future."

While it's just a beginning, Google has also launched a beta tool that allows businesses to upload their own floor plans to the Maps database. Slowly but surely, Google hopes to entice more businesses and major indoor areas of interest – both small and large – to opt in for indoor mapping. Of course, these are private spaces, not freely accessible public roads, so it's an initiative for the long haul.

The update is currently available in the Android Market for phones and tablets running Android version 2.1 and up.