1. Frequently Asked Questions
  2. Worldview Snapshots FAQs

Worldview Snapshots FAQs


What is Worldview Snapshots?

Worldview Snapshots is a lightweight tool for creating image snapshots from a selection of popular NASA satellite imagery layers. You can preview and download imagery in different band combinations and add overlays on the imagery of active fire detections, coastlines, borders and roads.

Worldview Snapshots offers satellite imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on board NASA's Aqua and Terra satellites and the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument on board the joint NASA/NOAA Suomi-National Polar orbiting Partnership (Suomi-NPP) satellite provided by the Global Imagery Browse Services (GIBS). Near real-time imagery through the Land, Atmosphere Near real-time Capability for EOS (LANCE) is available approximately 3 hours after satellite overpass.

Try out Worldview if you would like to use a fully featured, interactive interface for browsing all of the full-resolution satellite imagery provided by GIBS.

This tool is a replacement for the Rapid Response Subsets.

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How do I get an image of the same area every day?

There are two ways in which you can achieve this.

Method 1

  1. Set up you initial area-of-interest, desired base and overlay layers; resolution and file format within the Worldview Snapshots form interface.
  2. Click on "Preview".
  3. Locate the "Share Image" link, click on the link to copy link to the clipboard. You may check the "Shorten Link" button to get a shorter link for easier sharing. You may also check "Always show today" or "Always show yesterday" buttons to share imagery that changes daily relative to the UTC date. "Always show today" will display what imagery the satellite has collected so far but might not return an image if the satellite has not yet passed over that area/imagery has not yet been processed; "Always show yesterday" may be useful if you are in a different time zone and you would like to always get an image.
  4. Every time you come back to the link, you will get today's or yesterday's imagery!

Method 2

  1. Set up you initial area-of-interest, desired base and overlay layers; resolution and file format within the Worldview Snapshots form interface.
  2. Bookmark the browser URL.
  3. Every time you come back to the URL, you will get to preview and download today's imagery!

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What is the "Layer Date" of the imagery?

The Layer Date is the date the imagery was acquired in UTC (or Coordinated Universal Time).

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What is "Auto Scale"?

Auto Scale is where we scale the width of the image by the cosine of the latitude. At higher latitudes, it creates a better looking, more psuedo-equal area image. Auto Scale is unavailable in the Arctic and Antarctic projections.

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What projections are available?

  • Geographic - EPSG: 4326
  • Arctic - EPSG: 3413
  • Antarctic - EPSG: 3031

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What are the Base Layers?

There are 9 available imagery layers from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on board NASA's Terra and Aqua satellites and the joint NASA/NOAA Visible Infrared Imaging Radiometer Suite (VIIRS) instrument on board the Suomi-National Polar orbiting Partnership (Suomi-NPP) satellite. Near real-time imagery is available approximately 3 hours after satellite overpass.

A digital color image displayed on a monitor is composed of three different color channels: red, green, and blue. Satellite images are made by combining the reflected light detected by the sensor at various wavelengths (spectral bands) and making them into a single image. Below is a list of the true-color and false-color images that are provided, each tailored to highlight different land surface, atmospheric, and oceanic features.

Terra, MODIS, Corrected Reflectance, True Color | Aqua, MODIS, Corrected Reflectance, True Color

True Color: Red = Band 1, Green = Band 4, Blue = Band 3

These images are called true-color or natural color because this combination of wavelengths is similar to what the human eye would see. The images are natural-looking images of land surface, oceanic and atmospheric features. The downside of this set of bands is that they tend to produce a hazy image.

MODIS Corrected Reflectance vs. MODIS Surface Reflectance

The MODIS Corrected Reflectance algorithm utilizes MODIS Level 1B data (the calibrated, geolocated radiances). It is not a standard, science quality product. The purpose of this algorithm is to provide natural-looking images by removing gross atmospheric effects, such as Rayleigh scattering, from MODIS visible bands 1-7. The algorithm was developed by the original MODIS Rapid Response team to address the needs of the fire monitoring community who want to see smoke. Corrected Reflectance shows smoke more clearly than the standard Surface Reflectance product. In contrast, the MODIS Land Surface Reflectance product (MOD09) is a more complete atmospheric correction algorithm that includes aerosol correction, and is designed to derive land surface properties. In clear atmospheric conditions the Corrected Reflectance product is very similar to the MOD09 product, but they depart from each other in presence of aerosols. If you wish to perform a complete atmospheric correction, please do not use the Corrected Reflectance algorithm. An additional difference is that the Land Surface Reflectance product is only tuned for calculating the reflectance over land surfaces.

References: NASA Earthdata—Rapid Response FAQ; AMNH—Biodiversity Informatics, Band Combination; NASA Earthdata—Creating Reprojected True Color MODIS Images: A Tutorial

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Terra, MODIS, Corrected Reflectance, 7-2-1 | Aqua, MODIS, Corrected Reflectance, 7-2-1

False Color: Red = Band 7, Green = Band 2, Blue = Band 1

This combination is most useful for distinguishing burn scars from naturally low vegetation or bare soil and enhancing floods. This combination can also be used to distinguish snow and ice from clouds. Snow and ice are very reflective in the visible part of the spectrum (Band 1), and absorbent in Bands 2 (near infrared) and 7 (short-wave infrared, or SWIR). Thick ice and snow appear vivid sky blue, while small ice crystals in high-level clouds will also appear blueish, and water clouds will appear white.

Vegetation and bare ground

Vegetation is very reflective in the near infrared (Band 2), and absorbent in Band 1 and Band 7. Assigning that band to green means even the smallest hint of vegetation will appear bright green in the image. Naturally bare soil, like a desert, is reflective in all bands used in this image, but more so in the SWIR (Band 7, red) and so soils will often have a pinkish tinge.

Burned areas

Burned areas or fire-affected areas are characterized by deposits of charcoal and ash, removal of vegetation and/or the alteration of vegetation structure. When bare soil becomes exposed, the brightness in Band 1 may increase, but that may be offset by the presence of black carbon residue; the near infrared (Band 2) will become darker, and Band 7 becomes more reflective. When assigned to red in the image, Band 7 will show burn scars as deep or bright red, depending on the type of vegetation burned, the amount of residue, or the completeness of the burn.

Water

Liquid water on the ground appears very dark since it absorbs in the red and the SWIR. Sediments in water appear dark blue. Ice and snow appear as bright turquoise. Clouds comprised of small water droplets scatter light equally in both the visible and the SWIR and will appear white. These clouds are usually lower to the ground and warmer. High and cold clouds are comprised of ice crystals and will appear turquoise.

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Terra, MODIS, Corrected Reflectance, 3-6-7

False Color: Red = Band 3, Green = Band 6, Blue = Band 7

This combination is used to map snow and ice. Snow and ice are very reflective in the visible part of the spectrum (Band 3), and very absorbent in Bands 6 and 7 (short-wave infrared, or SWIR). This band combination is good for distinguishing liquid water from frozen water, for example, clouds over snow, ice cloud versus water cloud; or floods from dense vegetation. This band combination is only available for MODIS (Terra) because 70% of the band 6 sensors on the MODIS instrument on NASA's Aqua satellite failed shortly after launch.

Snow and Ice

Since the only visible light used in these images (Band 3) is assigned to red, snow and ice appear bright red. The more ice, the stronger the absorption in the SWIR bands, and the more red the color. Thick ice and snow appear vivid red (or red-orange), while small ice crystals in high-level clouds will appear reddish-orange or peach.

Vegetation

Vegetation will appear green in this band combination, as vegetation is absorbent in Bands 3 and 7, but reflective in Band 6. Bare soil and deserts will appear bright cyan in the image since it much more reflective in Band 6 and 7 than Band 3.

Water

Liquid water on the ground will appear very dark since it absorbs in the red and the SWIR, but small liquid water drops in clouds scatter light equally in both the visible and the SWIR, and will therefore appear white. Sediments in water appear dark red.

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Suomi NPP, VIIRS, Corrected Reflectance, True Color

True Color: Red = Band I1, Green = Band M4, Blue = Band M3

These images are called true-color or natural color because this combination of wavelengths is similar to what the human eye would see. The images are natural-looking images of land surface, oceanic and atmospheric features.

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Suomi NPP, VIIRS, Corrected Reflectance, M11-I2-I1

False Color: Red = M11, Green = I2, Blue = I1

This combination is most useful for distinguishing burn scars from naturally low vegetation or bare soil and enhancing floods. This combination can also be used to distinguish snow and ice from clouds. Snow and ice are very reflective in the visible part of the spectrum (Band I1), and absorbent in Bands I2 (near infrared) and M11 (short-wave infrared, or SWIR). Thick ice and snow appear vivid sky blue, while small ice crystals in high-level clouds will also appear blueish, and water clouds will appear white. The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument in on board the joint NASA/NOAA Suomi-National Polar orbiting Partnership (S-NPP) satellite.

Vegetation and bare ground

Vegetation is very reflective in the near infrared (Band I2), and absorbent in Band I1 and Band M11. Assigning that band to green means even the smallest hint of vegetation will appear bright green in the image. Naturally bare soil, like a desert, is reflective in all bands used in this image, but more so in the SWIR (Band M11, red) and so soils will often have a pinkish tinge.

Burned areas

Burned areas or fire-affected areas are characterized by deposits of charcoal and ash, removal of vegetation and/or the alteration of vegetation structure. When bare soil becomes exposed, the brightness in Band I1 may increase, but that may be offset by the presence of black carbon residue; the near infrared (Band I2) will become darker, and Band M11 becomes more reflective. When assigned to red in the image, Band M11 will show burn scars as deep or bright red, depending on the type of vegetation burned, the amount of residue, or the completeness of the burn.

Water

Liquid water on the ground appears very dark since it absorbs in the red and the SWIR. Sediments in water appear dark blue. Ice and snow appear as bright turquoise. Clouds comprised of small water droplets scatter light equally in both the visible and the SWIR and will appear white. These clouds are usually lower to the ground and warmer. High and cold clouds are comprised of ice crystals and will appear turquoise.

References: Earthdata: VIIRS

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Suomi NPP, VIIRS, Corrected Reflectance, M3-I3-M11

False Color: Red = M3, Green = I3, Blue = M11

This combination is used to map snow and ice. Snow and ice are very reflective in the visible part of the spectrum (Band M3), and very absorbent in Bands I3 and M11 (short-wave infrared, or SWIR). This band combination is good for distinguishing liquid water from frozen water, for example, clouds over snow, ice cloud versus water cloud; or floods from dense vegetation. The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument in on board the joint NASA/NOAA Suomi-National Polar orbiting Partnership (Suomi-NPP) satellite.

Snow and Ice

Since the only visible light used in these images (Band M3) is assigned to red, snow and ice appear bright red. The more ice, the stronger the absorption in the SWIR bands, and the more red the color. Thick ice and snow appear vivid red (or dark pink), while small ice crystals in high-level clouds will appear pinkish.

Vegetation

Vegetation will appear green in this band combination, as vegetation is absorbent in Bands M3 and M11, but reflective in Band I3. Bare soil and deserts will appear bright cyan in the image since it much more reflective in Band I3 and M11 than Band M3.

Water

Liquid water on the ground will appear very dark since it absorbs in the red and the SWIR, but small liquid water drops in clouds scatter light equally in both the visible and the SWIR, and will therefore appear white. Sediments in water appear dark red.

References: Earthdata: VIIRS

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Suomi NPP, VIIRS, Day/Night Band, ENCC (Nighttime imagery)

The VIIRS Nighttime Imagery (Day/Night Band, Enhanced Near Constant Contrast) layer shows the earth’s surface and atmosphere using a sensor designed to capture low-light emission sources, under varying illumination conditions. It is displayed as a grey-scale image. Sources of illumination include both natural and anthropogenic sources of light emissions. Lunar reflection can be used to highlight the location and features of clouds and other terrestrial features such as sea ice and snow cover when there is partial to full moon conditions. When there is no moonlight, natural and anthropogenic night time light emissions are highlighted such as city lights, lightning, auroras, fires, gas flares, and fishing fleets. This layer is useful for showing patterns of human activity and energy behaviors such as cities and highways, the holiday periods, the tracking of shipping and fishing fleets at night and, the burning of waste natural gas (gas flares) from on and off shore oil/gas production sites. The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument in on board the joint NASA/NOAA Suomi-National Polar orbiting Partnership (Suomi-NPP) satellite.

References: Lee, T., S. Miller, F. Turk, C. Schueler, R. Julian, S. Deyo, P. Dills, and S. Wang, 2006: The NPOESS VIIRS Day/Night Visible Sensor. Bull. Amer. Meteor. Soc., 87, 191–199, doi: 10.1175/BAMS-87-2-191; The Lights of London. NASA Earth Observatory; Out of the Blue and Into the Black. NASA Earth Observatory; Román, M. O. and Stokes, E. C. (2015), Holidays in lights: Tracking cultural patterns in demand for energy services. Earth's Future, 3: 182–205. doi: 10.1002/2014EF000285

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What are the Overlay Layers?

Fires

When you select Fires as your overlay layer, it will match the corresponding fire layer to the base layer you have picked. These are available approximately 3 hours after satellite overpass.

  • Terra/MODIS Corrected Reflectance layers: Terra/MODIS Fires and Thermal Anomalies (Day and Night) layer (8 May 2012 - present)
  • Aqua/MODIS Corrected Reflectance layers: Aqua/MODIS Fires and Thermal Anomalies (Day and Night) layer (8 May 2012 - present)
  • Suomi-NPP/VIIRS Corrected Reflectance layers: Suomi-NPP/VIIRS Fires and Thermal Anomalies (Day) layer (25 November 2015 - present)
  • Suomi-NPP/VIIRS Day/Night Band, ENCC: Suomi-NPP/VIIRS Fires and Thermal Anomalies (Night) layer (25 November 2015 - present)

Coastlines

The Coastlines layer is a vector layer displaying global coastlines. Coastlines information are gleaned from OpenStreetMap.

Coastlines, Borders and Roads

The Coastlines/Borders/Roads layer is a vector layer displaying global coastlines, country borders, first order administrative boundaries and major roads. Coastlines/Borders/Roads information are gleaned from OpenStreetMap and Natural Earth.

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What do the different band combinations mean for the corrected reflectance images?

A digital color image displayed on a monitor is composed of three different color channels: red, green, and blue. The Corrected Reflectance satellite images from MODIS and VIIRS are made by combining the reflected light detected by the sensor at various wavelengths (spectral bands) and making them into a single image. Worldview Snapshots makes use of the MODIS and VIIRS broad range of spectral observations by creating both true-color and false-color images, each tailored to highlight different land surface, atmospheric, and oceanic features.

MODIS and VIIRS Band Combinations
True-color: MODIS Bands 1, 4, 3; VIIRS Bands I1, M4, M3
Short Answer
MODIS Bands 1, 4, 3 (670 nm: 565 nm: 479 nm) / VIIRS Bands I1, M4, M3 (600-680 nm: 545-565 nm: 478-498 nm)

Advantages: Natural-looking images of land surface, oceanic and atmospheric features.

Long Answer
True-color imagery uses MODIS Bands 1, 4, and 3 or VIIRS Bands I1, M4, M3 respectively corresponding to the red, green, and blue range of the light spectrum, are assigned to the red, green, and blue channels of a digital image. These images are called true-color or natural color because this combination of wavelengths is similar to what the human eye would see. The images are natural-looking images of land surface, oceanic and atmospheric features.

MODIS Bands 3, 6, 7 or VIIRS Bands M3, I3, M11 combination
Short Answer
MODIS Bands 3, 6, 7 (479 nm: 1652 nm: 2155 nm) / VIIRS Bands M3, I3, M11 (478-498 nm: 1580-1640 nm: 2225-2275 nm)

Colors
Vegetation: Green
Ice or snow: Red
Liquid water on the ground: Black or dark red
Liquid water clouds: White
Ice clouds: Peach
Desert: Light blue-green

Advantages: Distinguishing liquid water from frozen water, for example, clouds over snow, ice cloud versus water cloud; or floods from dense vegetation.

Long Answer
The MODIS Band 3, 6, 7 or VIIRS Bands M3, I3, M11 combination are assigned to the red, green, and blue components of a digital image. This combination is used to map snow and ice. Snow and ice are very reflective in the visible part of the spectrum (MODIS Band 3/VIIRS Band M3), and very absorbent in MODIS Bands 6 and 7/VIIRS Bands I3 and M11 (short-wave infrared, or SWIR).

Snow and Ice
Since the only visible light used in these images (MODIS Band 3/VIIRS Band M3) is assigned to red, snow and ice appear bright red. The more ice, the stronger the absorption in the SWIR bands, and the more red the color. Thick ice and snow appear vivid red (or dark pink), while small ice crystals in high-level clouds will appear pinkish in the MODIS imagery and reddish-orange or peach in the VIIRS imagery.

Vegetation
Vegetation is absorbent in MODIS Bands 3 and 7/VIIRS Bands M3 and M11, but reflective in MODIS Band 6/VIIRS Band I3, and so will appear greenish in this band combination. Bare soil and desert will appear bright cyan in the image since it much more reflective in MODIS Band 6/VIIRS Band I3 and MODIS Band 7/VIIRS Band M11 than MODIS Band 3/VIIRS Band M3.

Water
Liquid water on the ground will appear very dark since it absorbs in the red and the SWIR, but small liquid water drops in clouds scatter light equally in both the visible and the SWIR, and will therefore appear white. Sediments in water appear dark red.
MODIS Bands 7, 2, 1 or VIIRS Bands M11, I2, I1 combination
Short Answer
MODIS Bands 7, 2, 1 (2155 nm: 876 nm: 670 nm) / VIIRS Bands M11, I2, I1 (2225-2275 nm: 846-885 nm: 600-680nm)

Colors
Vegetation: Green
Water: Black or dark blue
Desert/Naturally bare soil: Sandy pink
Burn scar: Red to reddish-brown, depending on the nature of the pre-fire vegetation and the severity of the burn.

Advantages: Distinguishing burn scars from naturally low vegetation or bare soil. Enhancing floods.

Long Answer
MODIS Bands 7, 2, and 1/VIIRS Bands M11, I2, I1, are assigned to the red, green, and blue portions of the digital image. This combination is most useful for identifying burn scars from naturally low vegetation or bare soil and enhancing floods. This combination can also be used to distinguish snow and ice from clouds. Snow and ice are very reflective in the visible part of the spectrum (MODIS Band 1/ VIIRS Band I1), and absorbent in MODIS Band 2/VIIRS Band I2 (near infrared) and MODIS Band 7/VIIRS Band M11 (short-wave infrared, or SWIR). Thick ice and snow appear vivid sky blue, while small ice crystals in high-level clouds will also appear blueish, and water clouds will appear white.

Vegetation and bare ground
Vegetation is very reflective in the near infrared (MODIS Band 2/VIIRS Band I2), and absorbent in MODIS Band 1/VIIRS Band I1 and MODIS Band 7/VIIRS Band M11. Assigning that band to green means even the smallest hint of vegetation will appear bright green in the image. Naturally bare soil, like a desert, is reflective in all bands used in this image, but more so in the SWIR (MODIS Band 7/VIIRS Band M11, red) and so soils will often have a pinkish tinge.

Burned areas
Burned areas or fire-affected areas are characterized by deposits of charcoal and ash, removal of vegetation and/or the alteration of vegetation structure. When bare soil becomes exposed, the brightness in MODIS Band 1/VIIRS Band I1 may increase, but that may be offset by the presence of black carbon residue; the near infrared (MODIS Band 2/VIIRS Band I2) will become darker, and MODIS Band 7/VIIRS Band M11 becomes more reflective. When assigned to red in the image, MODIS Band 7/VIIRS Band M11 will show burn scars as deep or bright red, depending on the type of vegetation burned, the amount of residue, or the completeness of the burn.

Water
Liquid water on the ground appears very dark since it absorbs in the red and the SWIR. Sediments in water appear dark blue. Ice and snow appear as bright turquoise. Clouds comprised of small water droplets scatter light equally in both the visible and the SWIR and will appear white. These clouds are usually lower to the ground and warmer. High and cold clouds are comprised of ice crystals and will appear turquoise.

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What is the maximum image size/dimension that I can download?

The maximum image size/dimension you can download is 8200 x 8200 pixels.

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Imagery Use and Citation Information

NASA supports an open data policy and we encourage publication of imagery from Worldview Snapshots; when doing so for image captions, please cite it as "NASA Worldview Snapshots" and also consider including a direct link to the imagery in Worldview Snapshots to allow others to explore the imagery.

For acknowledgment in scientific journals, please use: "We acknowledge the use of imagery from the Worldview Snapshots application (https://wvs.earthdata.nasa.gov/), part of the Earth Observing System Data and Information System (EOSDIS)."

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Last Updated: Aug 6, 2019 at 1:18 PM EDT