Anonymous ID: 65b2c7 Jan. 18, 2019, 9:14 p.m. No.4815397 🗄️.is 🔗kun >>5472 >>4815313 >and a modern magnetometer based on radiation. What? >>4815348 >I know the phone ones are hall effect, but with thousands run through an algorithm, I'm sure you could make a solid map. If you combined it with accelerometer and GPS data then perhaps.