In March, Matt Bratlien saw something odd in the spacious suburb of Silver Firs, north of Seattle. A six-wheeled robot with the Amazon Prime logo on its sky-blue carapace was driving up and down the sidewalks and curbs, watched by a company representative. “I was surprised, excited, and very curious,” says Bratlien, a partner at Net-Tech, an IT services company in nearby Bellevue.

Bratlien had encountered Scout, a delivery robot Amazon is testing in the area, including by ferrying real orders to customers. Here’s what he didn’t see: Countless digital clones crawling through a virtual copy of the neighborhood that Amazon created with scans of the area collected by lasers, cameras, and aircraft.

Amazon knows a lot about the world thanks to data from its vast retail business and cloud computing platform. It knows a 2-square-kilometer zone of Snohomish County in unusual detail—down to the position of weeds sprouting through the drainage grates. The company’s digital copy mirrors the position of curbstones and driveways within centimeters, and textures like the grain of asphalt within millimeters.

That synthetic suburb allows Amazon to test Scout thousands or perhaps millions of times under varying weather conditions without swarming the neighborhood with bright blue rovers until they become a nuisance. “The bots can run 24/7 in simulation,” says Sean Scott, the executive leading the project. The practice resembles how Waymo and others working on autonomous cars invest heavily in simulations to supplement miles driven on real roads.

Amazon wants Scout to help it deliver more packages, more promptly. The company recently said it would offer US members of its Prime service free next-day delivery. In January, Amazon said it was testing six of the robots somewhere in Snohomish County. It now says the fleet has grown, but declines to say exactly where they roam. County Executive Dave Somers says Amazon consulted him and the sheriff’s office prior to launching, and says he supports the project but doesn’t know exactly where Amazon tests.

Bratlien’s Facebook post geotagged Scout in Silver Firs, a community of 21,000 with curving streets branched with cul-de-sacs; another person posted a photo of Scout in the same neighborhood. Months after Amazon announced Scout was in testing, Washington Governor Jay Inslee signed a bill that regulates delivery robots, limiting their speed and weight and barring them from jaywalking.

Matt Bratlien posted this image on Facebook after encountering an Amazon robot in March.

Amazon’s mapping and simulation technology is not just a research tool. It could also help Amazon deploy the robots to new neighborhoods when they’re ready for general use, by first testing them in simulations. “We've built it such that we can scale up to an entire city,” Scott says. By the time Scout rolls into a new town for the first time, its control system will have likely “seen” every seam in the pavement thousands of times before.