Aursee · method

How detections become fires

The rule Aursee uses to turn individual satellite pixels into fires you can open, name and follow.

The problem

A single fire front lights up many neighbouring pixels, and several satellites see it in the same day. Listing pixels would turn one fire into dozens of entries. On 21 September 2026, grouping turned 150,469 detections into 26,397 fires.

The rule

Every detection in a complete 24-hour UTC window is placed on a grid of 0.02 degree cells, about 2.2 km at the equator and narrower towards the poles. Cells that contain detections and touch each other, including at the corners, are joined into one fire. The fire's position is the power-weighted centre of its detections.

The window is a full 24 hours rather than the current calendar day. A partial day would contain the afternoon pass for some longitudes and the night pass for others, and the share of detections seen at night would then describe the query rather than the fire.

What follows from it

Two separate fires closer than about 2 km merge into one. A long fire line broken by a gap wider than a cell becomes two fires. The span shown on a fire page is the width of the group, not a mapped perimeter.

Each fire is given the nearest settlement of at least 1,000 people from GeoNames, with the distance and bearing, so it has a name a reader can recognise.

More on the method

• What a satellite fire detection isHow VIIRS finds active fires from orbit, what a 375 m detection means, and when a fire is not seen.
• Fires in the dark: how satellites find them at nightWhy a fire is easier to see from orbit at night, how VIIRS picks a flame of a few dozen square metres out of a 375 m pixel, and what “burning in darkness” means on the map.
• Fire radiative power (MW)What fire radiative power measures, how Aursee adds it up, and how to compare two fires.
• The burn archive, 2012 to todayHow Aursee remembers where fire has been detected since 2012, and what the history figures on each page mean.
• Lightning near a fireHow Aursee checks for lightning before a fire was first seen, and where that check is possible.
• Land cover and roads under a fireWhat kind of ground a fire is burning on, and how many roads are around it: sources and resolution.
• Weather at a fireWhere the wind, humidity and temperature on a fire page come from, and at what time and resolution.
• Data sources and licencesEvery dataset Aursee uses, who publishes it, and the licence it is used under.