Guide
What a fire detection is
Each dot is a place a satellite saw heat. It is useful, and it is easy to over-read. Here is what we show and what we do to it.
Where the detections come from
The data is NASA's FIRMS, which publishes the last 24 hours of detections from three satellites carrying the VIIRS instrument: Suomi NPP, NOAA-20 and NOAA-21. NASA's LANCE page says near real-time users usually need data within three hours. We measured the newest detection in the files to be about two and a half hours old at the time we looked. We could not confirm the exact latency of these files from a NASA page.
What we leave out and what we group
- Detections marked low confidence are left out. On the day we checked, that was about 12 percent of rows. The app shows how many were left out. The class definitions are NASA's; we could not read NASA's own description of them, so we make no claim about what they mean beyond the label.
- Nearby detections are grouped into cells of a quarter of a degree, so a screen shows places, not individual pixels.
- The same fire seen by two satellites, or on two passes, counts twice. The screen says so.
What the dots do not tell you
A detection means a satellite instrument reported heat at that spot at that time. The app does not measure or estimate how large a fire is, and we have not verified how often each place is observed, so a place with no dots is not proof of no fire. For safety information, follow your local authorities.
NASA asks anyone using the data to follow its acknowledgement: we acknowledge the use of data and imagery from NASA's Land, Atmosphere Near real-time Capability for Earth observations (LANCE), part of NASA's Earth Science Data and Information System (ESDIS). NASA provides the information as is.
Sources
- NASA LANCE: FIRMS active fire data. Latency, terms and the acknowledgement text
- NASA FIRMS. The active fire files