Google is experimenting with a new way of collecting face data involving public places and gift cards.

As ZDNet reports, Google is sending out "many teams in many cities" armed with a modified smartphone and gift cards in an attempt to collect as much facial data as they can. If approached, the person will explain they are working for Google and collecting data to "improve the next generation of facial recognition phone unlocking." If you agree to help, an unknown smartphone in a large case will be handed to you with an instruction to move it around in selfie mode to capture your face from lots of angles.

Once the facial capture is over a waiver is signed and a gift card offered to the participant worth $5 for either Amazon or Starbucks. It seems likely that by agreeing to take part, signing the waiver, and accepting the gift card, participants are giving up their face data for Google to use as they want.

As to why Google is collecting this data, all the evidence points to the Pixel 4 which, as Android Police discovered last month, is expected to have a face authentication system just like Apple offers using Face ID on iPhone. Such a system needs to be trained, though, and that requires faces to train with. Clearly Google thought hitting public places with gift cards would be the best way to gather fresh data, and it seems to be working.

The latest Pixel 4 leak was for screen protectors sporting a new cutout expected to be for Google's Soli chip, which would allow for touchless interactions. There's also cutouts for two cameras, allowing for a Face ID-like system for securely unlocking your phone as long as it can recognize your face.

With the Pixel 4 expected to launch in October, Google still has a number of months to better-train its facial recognition system as long as it can gather enough training data. With that in mind, I suspect Google will end up being one of Amazon's and Starbucks' biggest customers for gift cards this year.

This article originally appeared on PCMag.com.