01 / Detection
Does a satellite detection mean there is a fire?
No. A detection marks a satellite pixel where an algorithm found a thermal anomaly. It needs further verification.
The heat source may be a wildfire, agricultural burning, industrial activity, or another strong source of heat. One point does not show a fire perimeter, burned area, or an official warning. NASA FIRMS describes a point as the center of a pixel containing one or more active fires or thermal anomalies.
02 / Time
How quickly does the data appear?
The data is near real time, not instant. Global NASA FIRMS products are generally available within three hours of the satellite observation.
Delays can be longer because of processing, transmission, or a temporary source outage. The map shows the last source check and the newest available detection so that users can judge data freshness.
What time period does the map show?
The dataset covers the previous 24 hours. Selecting 1, 3, 6, 12, or 24 hours changes which detections are treated as new. It does not extend the dataset beyond the previous 24 hours.
03 / Space
How accurate is a point location?
A point is the center of a satellite pixel. The actual heat source may be elsewhere inside that pixel.
A VIIRS pixel has a nominal size of 375 m. A MODIS pixel has a nominal size of 1 km. The observed area changes with viewing angle. A point should not be treated as an exact coordinate, a fire perimeter, or an estimate of burned area.
04 / Visibility
Why might a fire be missing from the map?
Satellites do not observe every place continuously. A fire may start and end between two overpasses. Other conditions may also prevent a detection:
- cloud, dense smoke, or vegetation obscures the heat signal;
- the source is too small or cool for the algorithm threshold;
- the satellite did not pass at the relevant time;
- data processing or delivery is delayed or temporarily unavailable.
05 / Instruments
What are VIIRS and MODIS?
VIIRS and MODIS are satellite instruments that measure energy in several parts of the electromagnetic spectrum. NASA FIRMS uses their products to identify active fires and thermal anomalies.
Its finer nominal resolution helps detect smaller heat sources and show more detail in larger fires.
A long-running observing program that adds continuity and more satellite overpasses.
What does FRP mean?
FRP is Fire Radiative Power. It is reported in megawatts and estimates the rate at which a heat source emits radiant energy at the time of the satellite overpass. FRP is not the size, diameter, or burned area of a fire. Values from different sensors need context before comparison.
06 / Grouping
How is a possible group formed?
At least three new detections are connected into a possible group within a 5 km radius during the selected period.
Groups with the most detections appear first. Grouping is only a fast way to review nearby points. It does not prove that the points belong to one fire and it is not an alert.
07 / Safety
How should the map be used?
The map is an informational view of public satellite data. Do not rely on it for decisions that affect people or property. Use official notices and instructions from the responsible authorities.
08 / References
Sources and further explanations
OSMATRAC does not change the meaning of NASA data. The following NASA Earthdata pages describe the products, latency, and limits used here.
- 01 NASA FIRMS — Fire Information for Resource Management System
- 02 What an active fire detection means on the ground
- 03 Available FIRMS products and typical latency
- 04 Reasons why a fire may not be detected
- 05 Active fire caveats and interpretation of FRP