Apple has quietly been working to rebuild its Maps application with self-gathered data, and will begin to roll out changes starting with the next beta of iOS 12, TechCrunch reports today. The process will apparently proceed slowly, starting only with data for San Francisco and the Bay Area, expanding to the rest of Northern California by fall 2018. It’s expected to continue across the United States for a full year, section by section.

Arriving as a replacement for iOS’ integrated Google Maps app, Apple’s Maps had a famously turbulent launch six years ago, complete with conspicuously missing and inaccurate third-party POI data, limited and poor directions, and other issues. Responding to complaints, Apple continued to refine the app annually, cleaning up its database and improving the UI. But the latest round of changes will go deeper.

According to today’s report, Apple’s new maps have been in the works for four years. They’re based upon data the company has gathered using both sensor-equipped vehicles and iPhones, and promise to provide markedly enhanced levels of detail. They will apparently acknowledge roadway and construction changes while offering more visibility concerning details like ground coverage, sporting areas, swimming pools, and walkways.

After remaining quiet on the topic, Apple acknowledged today that its sensor-laden Apple Maps vans have been gathering data for the project for years. They have been using a combination of eight high-resolution cameras, four lidar arrays, GPS, and a physical measurement tool to gather imagery and positional data.

What’s particularly new is the mention that “hundreds of millions of iPhones” will be gathering traffic information. Apple says that its approach has placed a premium on user privacy and that it’s effectively anonymizing data by not gathering start and endpoint data for individual users — just segments of what’s in the middle, so that a specific person’s overall trip and destinations can’t be viewed. Data will only be gathered when the Maps app is already in use, so the impact on battery life will be “near zero.”

By using that data, however, Apple will be able to gather real-time information on road conditions, road systems, new construction, and changes in pedestrian walkways. And the Maps team will now be able to make adjustments to roads and road conditions in near-real time, said Apple senior VP Eddy Cue, who is now in charge of the feature. He told TechCrunch:

For example, a road network is something that takes a much longer time to change currently. In the new map infrastructure, we can change that relatively quickly. If a new road opens up, immediately we can see that and make that change very, very quickly around it. It’s much, much more rapid to do changes in the new map environment.

Other improvements are coming as well, including a redesigned search feature, which currently routinely suggests irrelevant results that may not even be on your current continent. The report also says that Apple will be enhancing pedestrian guidance and navigation generally, as well as including parking areas and building details appropriate to your destination.

What’s unclear is the deadline for global completion, if there is any. While the United States will be updated over the next year, Apple apparently has not committed to launch dates for the map enhancements outside of its own home country, though it’s fair to assume that Maps’ international updates will overlap at least somewhat with the domestic ones.