You may occasionally notice that the acreage or containment shown in Watch Duty differs from a number reported somewhere else.

Watch Duty does not independently estimate a fire's acreage or containment. We rely on official incident information and fire perimeter data, which can be updated at different times and using different methods.

Where does fire acreage come from?

Acreage displayed in Watch Duty can come from official incident reports, including information provided by a fire's Public Information Officer (PIO), or from fire perimeters uploaded to the National Interagency Fire Center (NIFC).

When an active fire perimeter is available through NIFC, the acreage shown in Watch Duty is calculated directly from the mapped perimeter.

Why might the acreage be different from another source?

There are several reasons acreage figures can differ:

• The information was updated at different times. A fire can continue to grow after an acreage estimate or perimeter was created.
• A mapped perimeter may be older than the latest reported acreage. Fire perimeters are mapped and uploaded periodically, so they may not reflect fire growth that occurred afterward.
• A newer perimeter may become available before other official reporting is updated. In this case, the acreage calculated from the perimeter may differ from a previously reported figure.
• Early acreage figures are often estimates. Incident Command or Air Attack may provide an initial estimate before more precise mapping becomes available.

Because of these differences, two official sources can temporarily show different acreage figures for the same fire.

Where does containment information come from?

Watch Duty reports containment figures from official incident sources. We don't estimate or calculate containment ourselves.

If officials haven't provided a containment percentage, Watch Duty won't guess what it might be.

Containment figures can also change as new information becomes available, so another source may show a different percentage if it was updated at a different time.

For more information, see What Does Fire Containment Mean?.