Frequently Asked Questions

What do the fire hotspot symbols mean?

A fire symbol on the map indicates the approximate location of a “Hot Spot” detected by NASA’s MODIS or VIIRS satellites. A “Hot Spot“ is an area of the Earth’s surface that is radiating a large amount of heat, thus indicating a fire.

What do the different colors mean?

  • Yellow hotspots have been detected in the past 12 hours. Fires here are likely still burning strongly.
  • Orange hotspots were detected in the past 12-24 hours.
  • Grey hotspots were detected in teh past 48 hours – 7 days. Firers here are likely extinguished or smoldering.

Where does the hotpot data come from?

Hot Spots are detected by three NASA Earth Observing satellites. The Terra and Aqua satellites are equipped with MODIS sensors, while the Suomi NPP satellite carries the more modern VIIRS sensor. MODIS and VIIRS collect radiometric data about Earth’s surface, oceans, and atmosphere as they orbit the planet. Areas of intense heat are detected as Thermal Anomalies, i.e. fires.

What is MODIS?

“MODIS (or Moderate Resolution Imaging Spectroradiometer) is a key instrument aboard the Terra (originally known as EOS AM-1) and Aqua (originally known as EOS PM-1) satellites. Terra’s orbit around the Earth is timed so that it passes from north to south across the equator in the morning, while Aqua passes south to north over the equator in the afternoon. Terra MODIS and Aqua MODIS are viewing the entire Earth’s surface every 1 to 2 days, acquiring data in 36 spectral bands, or groups of wavelengths (see MODIS Technical Specifications).” Source: NASA

What is VIIRS?

VIIRS is a multi-disciplinary sensor providing data for the ocean, land, aerosol, and cloud research and operational users. VIIRS spectral coverage allows for data products similar to those from SeaWiFS as well as SST, a standard MODIS product. SST is an Essential Climate Variable (ECV) and, through validation with instruments traceable to NIST standards, is a Climate Data Record. Also, as with SeaWiFS and MODIS, the VIIRS scan and orbit geometries will provide global coverage every two days.” Source: Raytheon

How do I toggle between MODIS and VIIRS?

Click on the Legend Icon icon at the far left of the toolbar located in the blue section directly above the map. Click on “MODIS Hotspots” to toggle MODIS on and VIIRS off; click on “VIIRS Hotspots” to toggle VIIRS on and MODIS off.

How frequently are the hotspots updated?

Terra, Aqua, and Suomi NPP satellites each collect data from nearly every location on Earth approximately twice every 24 hours. Thus, there are generally 6 total hot spot updates for any given fire every day. We update our map hourly, meaning that if any of the three satellites make a pass over a location it will be on our map in no more than an hour.

Why are the MODIS and VIIRS hotspots different?

VIIRS collects data at a higher “spatial resolution” than MODIS. VIIRS gathers data with a spatial resolution of approximately 375 meters, whereas MODIS gathers data with a spatial resolution of approximately 1KM. MODIS, however, gathers data at a higher “temporal resolution.” MODIS data is updated twice as frequently as VIIRS, as it is on board two satellites (Terra and Aqua) to VIIRS’ one (Suomi NPP). Thus, the most complete model of fire conditions comes from a combination of VIIRS and MODIS data.

How accurate is the hotspot data?

Hotspots on will always be near the approximate real-world location of fires. VIIRS Hot Spots are no more than approximately 300 meters away from real world fire location, and MODIS Hot Spots are within approximately 800 meters of real world fire location.

How current is the hotspot data?

Hotspots on will always be near the approximate real-world location of fires. VIIRS Hot Spots are no more than approximately 300 meters away from real world fire location, and MODIS Hot Spots are within approximately 800 meters of real world fire location.

Why is the fire near me not on the map?

The fire may not be big enough to be detected by MODIS or VIIRS. Alternatively, there may not have been a satellite pass over the location since the fire began.

Why are there so many small fires in agricultural areas?

Throughout the year, farmers will burn off their old crops in order to remove old vegetation and prepare soil for new. If a single Hot Spot appears to be on or near cropland, it is likely nothing to be concerned about.

How do I find a specific fire?

If the fire has been assigned a GEOMac Perimeter:

Click on the Zoom Icon icon on the far right of the tool bar located on the blue strip above the map. A “Zoom to Perimeter” sidebar will appear. Simply scroll dwon the alphabetical list of current perimeters to find your targeted fire. Click the fire’s name to be zoomed to that perimeter. A GeoMAC sidebar will open with technical data about the selected fire.

If the fire has not been assigned a GEOMac Perimeter:

Use the zoom and pan tools to navigate to the approximate geographic location of the fire.

Where do the fire perimeters come from?

Fire perimeters are courtesy of GeoMAC, a USGS data service.

Why doesn’t the fire perimeter match the hotspots?

GeoMAC perimeters are usually updated once a day. Our hotspots  are generally more current than the perimeters.

General Terms


The measurement of distance north or south of the Equator at the earth’s surface.


The measurement of distance east or west of the Prime Meridian at the earth’s surface.

Map Interface

The collection of data layers and tools with which a user can interact.

Map View

The current representation of geographic datasets compiled by a user in the map interface.


A defined area of land owned by a legal entity.


Means by which a MapPort user creates map views or manipulates data.The visual representation of a geographic dataset.

Tool Bar


Keyboard Shortcuts

  • L – Layers/Legend panel
  • O – Zoombox
  • B – Back to previous map view
  • F – forward to previous map view
  • G – Google Street View
  • M – Metrics tools
  • D – Map Download
  • P – Print
  • S – Live URL Share
  • R – Refresh map
  • I – Information panel
  • Z – Zoom to perimeter

Mapport Tools


The visual representation of a geographic dataset.

Live Share

Map Download




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