I'm not sure of the exact sensor. There is a little more info on it here for example (https://www.mazdausa.com/static/manuals/2021/mazda3/contents...) but I can confirm the sensor placement is the same behind the windscreen, the lower one I think is by the badge. I wish they'd just made dashcam a standard feature instead and forget about trying to throw me through the windshield for shits and giggles.