Reading satellite hotspots

What the fields mean

Point

A detection has source coordinates. A marker locates that observation; it does not trace a fire perimeter or show the full affected area. Nearby or repeated detections can relate to the same incident.

Count

The matched count follows your selected circle, observation window and confidence filter within the retrieved file. It is a detection count, not a count of confirmed wildfires. If rows were rejected, only validated matches can be counted.

Observed at · UTC

This is satellite acquisition time. It does not tell you when a fire started or whether it is still burning. UTC is a shared time reference, which may differ from your local calendar date.

FRP · MW

Fire radiative power is a source measurement in megawatts. It does not give burned hectares, a fire’s perimeter, its cause or a spread forecast. An absent FRP value means the measurement was not provided.

Detection confidence

This VIIRS product uses low, nominal and high categories. Confidence concerns the detection, not danger to people or property. Unknown means no recognized category is available; high does not mean high wildfire risk.

For the product’s fields and qualifications, see NASA’s VIIRS Collection 2 Active Fire 375 m user guide (PDF). Numeric MODIS confidence scores are a different product convention.

Separate observation time from retrieval time

Last fetched records when this app retrieved the source file. For a hypothetical example, a point observed at 12:00 UTC in a file fetched at 12:20 UTC is a 12:00 observation. Fetching that same file again at 13:00 does not make the point a 13:00 observation.

Read the visible source state too. A snapshot retains older data after a failure; a historical replay uses a fixed past analysis clock and an incomplete sample. Neither becomes live because you open the page today. A retrieval failure is distinct from a valid selection with no matches.

Know which observations you are seeing

WildfireAgent.si retrieves one public Suomi NPP VIIRS Collection 2 global 24-hour file. It does not merge every satellite. The selected 6, 12 or 24 hours filter actual acquisition timestamps; the file’s name does not establish freshness.

The map, list, hourly chart and CSV use up to the newest 1,000 matching observations. A larger qualified matched count can therefore exceed the plotted and exported subset. Narrow the area or time window to examine a more focused selection; check the matched and plotted labels before quoting a total.

For example, eight plotted points would not establish eight separate wildfires. Likewise, a hypothetical 15 MW reading would not establish 15 hectares burned. These examples describe interpretation, not current observations.

Missing points do not establish absence or safety

A fire can occur between satellite overpasses, or its detection can be obscured by clouds, heavy smoke or tree canopy. NASA describes these gaps in its FIRMS acquisition and missed-detection notes. An empty selection only describes matching records in this app’s retrieved data.

Check the issuing source

In the explorer, open Sources & data limits for the exact dataset, fetched time and observation range. Compare with the official NASA FIRMS viewer and check NASA’s current downloads and source notices; available sensors and dates can differ between views.

For incident status and local instructions, consult the responsible authorities. Try the California workflow or Brazil workflow for a practical starting point.