Colours the big number against a recommended trolling speed for whatever you're after — green inside the range, amber near it, red well outside. The starting numbers are a decent opening guess, not gospel: every species is editable, and you can add your own.

Roughly how long the big number takes to catch up after you change the throttle. Longer gives a calmer number you can trust at a glance; shorter reacts faster but wanders. Raw GPS at trolling speed is noisy enough that some smoothing always helps — watch the Live figure to see what the unfiltered reading is doing.

Feeds invented GPS fixes through the exact same filter as the real thing, so you can see how it behaves without leaving the dock. Real GPS is ignored while this is on.

Open source, and it collects nothing — no analytics, no accounts, no network requests. Your position is read, shown on screen, and discarded.

Accuracy is how precisely the receiver reports knowing your position. It is not reception strength — GPS is receive-only, so there is no connection to drop — and it is not speed accuracy, which the browser never exposes. Speed comes from Doppler shift and stays good even when this figure does not.

Those two differ while you are stopped: the receiver keeps reporting a position but declines to put a speed on it, because at a standstill it cannot tell real motion from its own noise. Long gaps when moored are normal — iOS throttles updates hard when nothing is moving.