Frequently Asked Questions

Active Fire Data

What is a MODIS hotspot/fire detection?
How are hotspots/fires detected?
What size hotspot/fires can be detected?
When were the Terra and Aqua Satellites launched?
What are the Terra and Aqua orbit tracks?
How do I know if a hotspot/fire detection was missed due to cloud?
What are the attributes of the hotspot/active fire data?
What is the detection confidence?
What does the confidence value mean?
What does scan and track mean?
What is the brightness temperature?
What are Collections?
What are the known improvements to Collection 5?
How appropriate are hotspot/fire detections for research?
Can you use the MODIS active fire product for detecting volcanoes?
What is the plan after MODIS?
What is NPP?
What is VIIRS?
What other types of hotspot/fire data are available?
Citation Information

MODIS Rapid Response System Status
MODIS Fire User Guide


Related Products

What other products are available?

Web Fire Mapper

What is Web Fire Mapper, and at who is it aimed?
If I see a hotspot/fire on Web Fire Mapper - what does that mean on the ground?
How often are the hotspots/fires updated on Web Fire Mapper?
Can I download the hotspot/fire data from Web Fire Mapper?
Why does Web Fire Mapper cover selected areas only?
Can I get information on burned areas from Web Fire Mapper?

Email Alerts

Can you notify me when a hotspot/fire occurs in my area?
How do I edit my subscription?
I can't see the administrative boundaries, where are they?
How do I add a CSV file as a layer in ArcMap?
How do I add a CSV file as a layer in ArcView?
Why do I receive more than one near real time alert in any given satellite overpass period?

Data Formats

Available Data Formats for hotspot/fire information

 

MODIS Rapid Response System Status

The MODIS hotspot/active fire data is provided by the MODIS Rapid Response System. For more information about MODIS Rapid Response, see http://rapidfire.sci.gsfc.nasa.gov.

For information on the system status of MODIS Rapid Response, see http://rapidfire.sci.gsfc.nasa.gov/status/

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MODIS Fire User Guide

For more information on the active hotspot/fire product and other MODIS fire products, please refer to the MODIS Fire User Guide. Click here to open PDF (2.5MB)

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What is a MODIS hotspot/fire detection?

A MODIS hotspot/fire detection is the location of a thermal anomaly that was detected by MODIS using data from the middle infrared and thermal infrared bands. In most cases, this thermal anomaly is a fire, but sometimes it is a volcanic eruption or the flare from a gas well. We have no way of knowing which it is based on the MODIS data alone.

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How are hotspots/fires detected?

The hotspot/fire detections are produced using the same algorithm as the standard MODIS MOD14 fire and thermal anomalies product. Fire detection is performed using a contextual algorithm that exploits the strong emission of mid-infrared radiation from fires. The algorithm examines each pixel of the MODIS swath, and ultimately assigns to each one of the following classes: missing data, cloud, water, non-fire, fire, or unknown.

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What size hotspots/fires can be detected?

In any given scene the minimum detectable fire size is a function of many different variables (scan angle, biome, sun position, land surface temperature, cloud cover, amount of smoke and wind direction, etc.), so the precise value will vary slightly with these conditions.

Stage 2 validation is nearing completion through analysis of a large number of ASTER (high resolution satellite) data for a wide range of conditions over selected regions and time periods, combined with simulation results. These results indicate that in many biomes the minimum flaming (~800-1000K) fire size typically detectable at 50% probability with MODIS is on the order of 100m². Under ideal conditions performance is somewhat better. Such conditions occur when a fire is observed at (or near) nadir on a fairly homogeneous surface, no other significant fires are nearby, and the scene is free of clouds, heavy smoke and sun glint. In these circumstances the smallest flaming fire that can be routinely detected (i.e. near 100% probability of detection) is approximately 50 m² in size.

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When were the Terra and Aqua Satellites launched?

Terra was launched 18 December 1999 and Aqua was launched 4 May 2002. High quality observations are avaliable from November 2000 onwards.

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What are the Terra and Aqua orbit tracks?

The Space Science and Engineering Center (SSEC) at University of Wisconsin-Madison provides daily Terra and Aqua global and regional orbit tracks.

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How do I know if a hotspot/fire detection was missed due to cloud?

An indication of cloud cover is not yet included in Web Fire Mapper. If you want to know whether the MODIS Rapid Response system may have omitted to detect some hotspots/fires due to cloud, you can look on the MODIS Rapid Response Real-Time website. There you can view the MODIS near-real-time level 2 browse images which clearly show cloud at the time of overpass.

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What are the attributes in the hotspot/active fire data?

Latitude and Longitude: The center point location of the hotspot/active fire within a 1 km pixel.
Brightness: The brightness temperature, measured (in kelvins) using the MODIS channels 21/22.
Scan and Track: The actual spatial resolution of the scanned pixel.
Acqdate: Acquisition date the hotspot/fire pixel.
Time: Time of the overpass of the satellite.
Satellite: Whether the detection was picked up by the Terra or Aqua satellite.
Confidence: The detection confidence is a quality flag of the individual hotspot/fire pixel.

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What is the detection confidence?

A detection confidence intended to help users gauge the quality of individual hotspot/fire pixels is included in the Level 2 fire product. This confidence estimate, which ranges between 0% and 100%, is used to assign one of the three fire classes (low-confidence fire, nominal-confidence fire, or high-confidence fire) to all fire pixels within the fire mask. In the Collection 4 fire product this confidence estimate does not adequately identify highly questionable, low confidence fire pixels. Such pixels, which by design should have a confidence close to 0%, are too often assigned much higher confidence estimates of 50% or higher. This will be corrected for Collection 5.

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What does the confidence value mean?

A confidence value for each hotspot/fire is stored in the attribute information and can be accessed using the Identify tool in Web Fire Mapper. The confidence value is based on a collection of intermediate algorithm quantities used in the detection process. The range of confidence is expressed between 0-100 (the values range from 0=very low to 100=very high). The confidence field is experimental and should be used with caution; it is likely that it will vary in meaning in different parts of the world. Nevertheless some of our end users have found such a field to be useful in excluding false positive occurrences of fire.

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What does scan and track mean?

It should be noted that the pixel size is not always 1km across the scan track. The pixels at the "Eastern" and  the "Western" edges of the scan are bigger than 1km. It is 1km only along the nadir (exact vertical from the satellite). Thus, the values shown for scan and track represent the actual spatial resolution of the scanned pixel. The scan value represents the spatial-resolution in the East-West direction of the scan and the track value represents the North-South spatial resolution of the scan.

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What is the brightness temperature?

The brightness temperature of a hotspot/fire pixel is measured (in kelvins) using the MODIS channels 21/22.

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What are Collections?

Reprocessing of the entire MODIS data archive is periodically performed to incorporate better calibration, algorithm refinements, and improved upstream products into all MODIS products. The updated MODIS data archive resulting from each reprocessing is referred to as a collection . Later collections supersede all earlier collections.

For the Terra MODIS, Collection 1 consists of the first products generated following launch.Terra MODIS data were first reprocessed for the first time in June 2001 to produce Collection 3. Note that this first reprocessing was numbered Collection 3, rather than Collection 2, as one would expect. Collection 3 was also the first produced for the Aqua MODIS products. Collection 4 reprocessing was initiated in December 2002 for the Terra MODIS, and somewhat later for the Aqua MODIS, and it forms the current archive of the MODIS products. Currently, Collection 5 reprocessing is scheduled to begin in early 2007.

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Known improvements with Collection 5

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How appropriate are hotspot/fire detections for research?

Hotspot/fire detections may not always be the most appropriate source of fire-related information. The shapefiles do not provide any information on cloud cover or missing data. Depending on the sort of analysis you are performing, it is sometimes possible to derive misleading (or even incorrect) results by effectively ignoring the other types of pixels. In some cases it is more appropriate to use one of the 1- km Level 3 or CMG fire products. (For more information, refer to the MODIS Collection 4 Active Fire Product User's Guide)

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Can you use the MODIS active fire product for detecting volcanoes or volcanic eruptions?

The algorithm routinely detects active volcanoes but the active fire product has not been validated against independent data for its ability to detect volcanoes.
There is a separate near-real time MODIS product specifically for volcanes -MODVOLC.

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What is the plan after MODIS?

The Visible Imaging Infrared Radiometer Suite (VIIRS) is being developed to extend the measurement series of the MODIS sensor, currently flying aboard EOS' Terra and Aqua satellites. The VIIRS sensor is part of the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP) - a joint NASA/IPO instrument risk reduction project.

NPP is scheduled to launch into a 515 mile orbit in summer 2010.

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What is NPP?

NPP is the NPOESS (National Polar-orbiting Operational Environmental Satellite System) Prepratory Project. It is a joint mission between NASA and the NPOESS Intergrated Program Office (IPO). NPP's mission is to collect and distribute remotely sensed data for the land, ocean and atmosphere for meteorological and global climate change studies. It allows for the transition from Earth observing (EOS) missions carried out by satellites such as Terra and Aqua to NPOESS. NPP will provide data such as atmospheric and sea surface temperatires, humidity soundings, land and ocean biological productivity, and cloud and aerosol properties.

NPP will feature the following sensors:

Advanced Technology Microwave Sounder (ATMS)

Cross-track Infrared Sounder (CrIS)

Ozone Mapping and Profiler Suite (OMPS)

Visible/Infrared Imager Radiometer Suite (VIIRS)

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What is VIIRS?

The Visible Imaging Infrared Radiometer Suite (VIIRS) will be similar to the MODIS sensor but will utilize more bands and more refined and advanced algorithms, resulting in greatly enhanced imaging and data collection. Through advances in technology and building upon sensors such as MODIS, SeaWiFS, POES' Advanced Very High Resolution Radiometer (AVHRR) and DMSP's Operational Linescan System (OLS), VIIRS is a smaller and less complicated sensor.

VIIRS uses a multi-spectral scanning radiometer with 12 bit quantization and measures 22 bands between 0.4 and 12 microns. The swath width is 3000 km. The imagery spatial resolution is 370 meters at nadir or 740 meters depending on the spectral band.

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What other types of active hotspot data are available?

AVHRR – Advanced Very High Resolution Radiometer

AVHRR measures electromagnetic radiation (light reflected and heat emitted) from our planet. AVHRR was originally intended only as a meteorological satellite system but it does have applications for fire monitoring. AVHRR remotely senses cloud cover and sea surface temperature, enabling its visible and infrared detectors to observe trends in vegetation, clouds, shorelines, lakes, snow and ice. The visible bands can detect smoke plumes from fires as well as burn scars. The thermal infrared band can detect actual hotspots and active fires. Its ability to detect fires is greater at night, since the system can confuse active fires with heated ground surfaces, such as beach sand and asphalt.

Active fire mapping on a global scale using a single satellite system has been coordinated by the International Geosphere Biosphere Program (IGBP) using AVHRR data for 1992-93 from international ground stations.

In addition, a small number of countries have developed their own regional AVHRR satellite fire monitoring systems using direct read-out; e.g., Brazil, Russia, and Senegal. Research groups have provided regional examples of trace gas and particulate emissions from fires for Brazil, Southern Africa, Alaska.

GOES – Geostationary Operational Environmental Satellite

The Geostationary Operational Environmental Satellites (GOES) house a five-channel (one visible, four infrared) imaging radiometer designed to sense radiant and solar reflected energy from sample areas of the Earth. They are stationed in orbits that remain fixed over one spot on the equator, providing continuous coverage of one hemisphere. GOES satellites acquire images every 15–30 minutes, at up to 1km resolution in visible light, for the detection of smoke, and 4km resolution in thermal infrared to directly detect the heat of fires.

MSG SEVIRI – Meteosat Second Generation (MSG) Spinning Enhanced Visible and Infrared Imager (SEVIRI)

The Meteosat Second Generation (MSG) satellite houses the optical imaging radiometer called the Spinning Enhanced Visible and Infrared Imager (SEVIRI). The sensor features 12 spectral channels and will provide cloud imaging and tracking, fog detection, measurement of the Earth surface and cloud top temperatures, tracking ozone patterns, as well as active fire monitoring.

The nominal coverage of the satellite includes the whole of Europe, all of Africa and locations at which the elevation to the satellite is greater than or equal to 10°. The various channels provide measurements with a resolution of 3 km at the sub-satellite point. The High Resolution Visible (HRV) channel provides measurements with a resolution of 1 km.

The Active Fire Monitoring (FIR) product is an image-based product in 3 km resolution that displays information on the presence of fire within a pixel and a product will be generated every repeat cycle, every 15 minutes.

The service, which commenced operations in January 2004, is due to continue until at least 2018.

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Citation Information

Please include a bibliographic citation for the hotspot/fire data that you use in your publications. Such citations will enable others to find the data and see how they have been used.

The following reference is for the FIRMS website and project:

Davies, D.K., Ilavajhala, S., Wong, M.M., and Justice, C.O. (2009). “Fire Information for Resource Management System: Archiving and Distributing MODIS Active Fire Data”. IEEE Transactions on Geoscience and Remote Sensing 47 (1):72-79.

The following reference provides a brief description of Web Fire Mapper website:

Justice, C.O., Giglio, L., Korontzi, S., Owens, J., Morisette, J.T., Roy, D., Descloitres, J., Alleaume, S., Petitcolin, F., and Kaufman, Y. (2002). The MODIS fire products. Remote Sensing of Environment 83, 244-262

The following reference provides a brief description of the algorithm used to produce the MODIS active fire detections:

Giglio, L., J. Descloitres, et al. (2003). "An Enhanced Contextual Fire Detection Algorithm for MODIS." Remote Sensing of Environment 87(2-3): 273-282.

Online reference:

NASA/University of Maryland, 2002. MODIS Hotspot / Active Fire Detections. Data set. MODIS Rapid Response Project, NASA/GSFC [producer], University of Maryland, Fire Information for Resource Management System [distributors]. Available on-line [http://maps.geog.umd.edu]

Please notify us of your publications that use the MODIS hotspot / active fire data. We would like to get a copy of your reprint, but reprints are not available, we request a bibliographic citation to your work. Using this information, we can provide information to the user community on how the fire data have been used, and we can keep our product-related references current.

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What other products are available?

In addition to the near real time hotspot/fire maps, Web Fire Mapper provides yearly global animations of monthly hotspots/fires. The global animation is created from monthly subsets to provide a synopsis of the burning pattern. The global animation cycles through an entire year to show the spatial and temporal variation of the burning in different parts of the world. These images help provide an understanding of the global pattern of hotspots/fires. All these images can be accessed from the Resources page.

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What is Web Fire Mapper, and who is it aimed at?

Web Fire Mapper is an internet based mapping tool that delivers locations of hotspots/fires in near real time. For selected regions and countries you can view an interactive map showing hotspots/fires for a specified time period, combined with your choice of GIS layers and satellite imagery.

Each hotspot detection represents the center of a 1 km pixel flagged as containing one or more actively burning hotspots/fires within that pixel. The hotspots/fires are detected using data from the MODIS (or Moderate Resolution Imaging Spectroradiometer) instrument, on board NASA's Aqua and Terra satellites.

Web Fire Mapper is primarily aimed at supporting natural resource managers, by helping them understand when and where hotspots/fires occur.

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If I see a hotspot/fire on Web Fire Mapper - what does that mean on the ground?

Each hotspot detection represents the center of a 1 km (approx.) pixel flagged as containing one or more active hotspots/fires within that pixel. The "location" is the centre point of the pixel (not necessarily the coordinates of the actual fire). The hotspot/fire is often less than 1km in size (see: What size hotspots/fires can be detected?). We are not able to determine the exact hotspot/fire size, what we do know is that at least one hotspot/fire is located within that 1 km pixel. Sometimes you will see several active hotspots/fires in a line. This generally represents a fire front.

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How often are the hotspots/fires updated on Web Fire Mapper?

Web Fire Mapper is updated throughout the day; it takes approximately 2-4 hours after the satellite overpass to process the data and update the website. To find out what time the satellite passes overhead you can check the MODIS orbit tracks via the link on the MODIS Rapid Response Real-time webpage.

Occasionally hardware errors mean that it takes longer than 2-4 hours to process the data.

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Can I download the hotspot/fire data from Web Fire Mapper?

Active hotspot/fire shape files for the last 48 hours and last 7 days are available for download. Click here to go to the download page. The full dataset will be made publically available when the data have been re-processed using the Collection 5 algorithm. MODIS Rapid Response was developed to provide rapid access to MODIS data, using experience gained in supplying information to the US Forest Service during the Montana fires of 2000. Since that time the MODIS Rapid Response team have made several adjustments to the fire detection algorithm. Data are currently being reprocessed using the latest algorithm to enable data from one time period to be compared directly with that of another.

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Why does Web Fire Mapper cover selected areas only?

When Web Fire Mapper started, it displayed global data. It was soon recognized that natural resource managers needed more specific GIS layers of their area to make the data meaningful. A number of country sites have been developed in collaboration with partners - as you will see the GIS layers vary from one site to another according to specific needs and what GIS layers are available.

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Can I get information on burned areas from Web Fire Mapper?

Not yet, but we plan to include a MODIS burned area product in the near future.

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Can you notify me when a hotspot/fire occurs in my area?

Yes, we have developed a global hotspot/fire warning system to notify natural resource managers when a hotspot/fire occurs in, or near, a specified area of interest, country or protected area. The beta version system is available for testing.

Click here to subscribe, or learn more about the email based alert system.

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How do I edit my subscription?

Visit the Global Fire Email Alerts page
- Enter your email address under the “Create/View Subscriptions” box. (This email should be the same email address you entered while subscribing).
- Click on “Proceed”
- On the next page, you will be shown a list of subscriptions you have under that email address
- Click on the “pencil” icon to edit your subscription.
- You will see a pop up alerting you if you want to overwrite your subscription. Click “OK”
- On the next page, choose your new map extent using the interactive map or choose a different country and/or protected area.
- Click “Edit Subscription”.

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I can't see the administrative boundaries, where are they?

In order to see the adminstrative boundaries on the email alerts system, visit the Global Fire Email Alerts page and log in with your email address.
Once you have logged in, proceed to the subscriptions page by either creating a new subscription or by editing one of your existing subscriptions. Then, choose the interactive map option, and zoom in using the zoom-in tool provided. Once you zoom in considerably to an area, you should be able to see the administrative boundaries.

Administrative Boundaries provided by ESRI.
ESRI “World Administrative Units” 2005 – Copyright Environmental Systems Research Institute (ESRI), 2005.

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I have received a CSV file as part of my Email Alert, how do I add it as a layer in ArcMap?

- Open ArcMap and go to ‘Tools’ on the Main Menu
- Select ‘Add XY Data’
-Navigate to the location of your .csv file and select the file
It should automatically select:
X Field: Longitude
Y Field: Latitude
Then you should select the Coordinate System
- Click ‘Edit...’ then the ‘Spatial Reference Properties’ window will open
- Click on ‘Select’
- Select ‘Geographic Coordinate System’ > ‘World’ > ‘WGS 1984’
- Click Add and click OK.

To permanently save your detected hotspots/fires layer as a shapefile:
- Right-click on the layer
- Select ‘Data’ > ‘Export Data’ and enter the file name with the .shp extension
- Click OK.

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I have received a CSV file as part of my Email Alert, how do I add it as a layer in ArcView?

- Re-name the extension of the CSV file to .txt
- Open ArcView
- Click on ‘Tables’ in the Project window and select 'Add'
- Change ‘List Files of Type’ to ‘Delimited Text (*.txt)’ and navigate to the .txt file, select and click OK
- Select the View window
- Go to 'View' on the Main Menu > ‘Add Event Theme’
- The Add Event Theme window will open with the following automatically selected:
Table: The .txt file that you selected
X Field: Longitude
Y field: Latitude
- Click OK and your hotspot/fire points will show up in the View window

To permanently save your detected hotspot/fire points as a shapefile:
- Select the fire points theme in the View window
- Go to 'Theme' on the Main Menu > ‘Convert to Shapefile...’
- Give it a file name with .shp extension
- Click OK.

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Why do I receive more than one near real time alert in any given satellite overpass period?

The MODIS sensor is on board two polar orbiting satellites, Terra and Aqua. Each satellite makes two overpasses over the globe, 2 day time and 2 night time overpasses, equaling to a total of 4 overpasses of the MODIS sensor in a 24 hour period. The sensor images the earth in 2330 km swaths. If you subscribed to a large area, like the USA, you will receive multiple near real time email alerts for a given overpass (e.g. Terra daytime overpass) as it takes several swaths to cover the whole of the US.

To determine where and when the overpass is going to occur, you may refer to the Terra and Aqua Orbit Tracks from the following websites.
Terra: http://www.ssec.wisc.edu/datacenter/terra/GLOBAL.html
Aqua: http://www.ssec.wisc.edu/datacenter/aqua/GLOBAL.html

The maps show a series of white lines with tic marks showing what time the satellite will pass over a certain location on the Earth. The white lines represent the center of the swath and the tic marks and time show at what time in UTC the satellite has passed over that location. (Please refer to the MODIS RR FAQ for more information: http://rapidfire.sci.gsfc.nasa.gov/faq/#faq04)

If you wish to view the MODIS near real time swath image that corresponds to the active fire detections, please go to the following website: http://rapidfire.sci.gsfc.nasa.gov/realtime/

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Data Formats

* Regional datasets include: Australia, South Africa, Central and South America, Europe, North America, South East Asia, Central and Northern Africa and Russia.

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