Point an industrial line-scan camera — built to inspect fast-moving conveyor belts, reading its single-pixel-wide sensor almost 19,000 times a second — out a moving train’s window, and each read becomes one column of a photograph. An onboard accelerometer clocks the train’s actual speed so consecutive columns stretch or compress to match reality before thousands of them stitch into one continuous slit-scan image. One ferry crossing alone produced a 56,894-by-2,048-pixel scan of San Francisco Bay.