EmberStrike

Usually, yes — but read it as "no satellite pass recorded anything hot here recently", not as "nothing is burning". An empty map at four in the afternoon can be followed by a dozen detections at six, when the next pass comes over.

The instruments see heat, not fire. Industrial flares, steel works, burning stubble, landfill fires and occasionally a sun-glint on a metal roof all land in the feed. That is exactly why the card shows you the confidence level: low-confidence pixels are the ones most likely to be something other than a wildfire.

Three ordinary reasons: the satellite has not passed over since it started; thick cloud or dense smoke hid the ground from the instrument; or the fire is smouldering under a canopy and too cool to stand out. The feed is a record of what was seen from orbit, not a register of fires.

They come from the instrument's own assessment of the pixel. The two instrument families report confidence in different ways, and the app folds both onto one three-step scale so a mixed map stays comparable. In Profile you can set the minimum confidence that is allowed to raise an alert.

Fire radiative power — how much energy the instrument measured leaving that pixel. Bigger generally means a more intense fire, and it is why some dots are drawn larger than others. It is not a measure of the burnt area.

The map stamps the age of its data on itself. A recent answer is reused instead of being fetched again — panning, switching tabs and coming back from the background all reuse it — and Profile lets you set how often a new one is pulled: every 15, 30, 60 or 180 minutes. The filter above the map chooses whether you see the last day, two days or week.

Four things have to hold at once. The detection must be one the app has not shown you before; it must fall inside the radius of one of your places; its confidence must be at or above your threshold; and it must be newer than the period you are filtering by.

If any one of them fails, no banner is raised. The Log still records the detection, so you can look back and see what was inside the radius without being woken for it.

Work down this list: permission actually granted in iOS Settings; alerts switched on in Profile; the place has a radius you have not set larger in your head than on screen; the confidence threshold not raised above what the nearby detections carry; and quiet hours, which default to 23:00–07:00.

Quiet hours never delete an alert. It waits and arrives when the window ends — a fire alert that is silently thrown away would be worse than a late one.

Pick the distance at which you would start doing something: packing, calling a neighbour, moving the car. For a house in the woods that tends to be five or ten kilometres; for a valley you drive through, twenty-five or fifty. A wide radius means more alerts, and a stream of alerts you stop reading is worse than none.

A route is up to five stops, and the corridor between them is watched as well as the stops themselves. It reports the riskiest leg, which is the thing you want before setting off rather than a list of points.

Yes. A notification carries a "Mute 2h" action alongside "Open map". The mute is temporary and applies to that alarm, not to the app.

A detection is announced once. The pixel keeps showing on the map and in the Log for as long as the feed carries it, but the same detection does not raise a second banner. A new pass producing a new detection does.

Heat detections come from NASA's FIRMS feed — the VIIRS instruments on Suomi NPP, NOAA-20 and NOAA-21, plus MODIS on Terra and Aqua. The danger forecast layer comes from the European Forest Fire Information System. Profile has a "Where the data comes from" screen that names them and links out. Everything the app prints — distance, bearing, which leg of a route is worst — is arithmetic on those feeds, calculated on your phone.

No. Places, radii, the log, your profile name and picture and all settings are stored on the device. There is no account to create and no server of ours holding a copy. Asking the satellite feed for a region means asking about a rectangle on the map, not about you.

The access key for the satellite feed is missing from that build. Nothing you can fix from inside the app — write to us and say which version you have. The rest of the app, including your saved places, is unaffected.

Partly. The last successful answer is kept on the device, so the map opens with what it had, clearly stamped with its age. Nothing new arrives until there is a connection again. After a failure the app waits and retries, spacing attempts further apart up to half an hour, and never throws away the map you already have.

None. The app is free and complete; there is no paywall anywhere in it and nothing is held back.

Only to let you choose a profile picture. It is optional, the picture is stored on the device, and skipping it changes nothing about the map or the alerts.

It concerns attribution: whether we can tell which campaign led to an installation and how that campaign performed. It has no effect on the fire data, your places or your alerts, and declining it leaves the app working exactly as before.

Profile → Reset data clears places, routes, the log and your settings in one action. Deleting the app removes everything as well, since nothing is stored anywhere else.