BCC Geospatial Center of the CUNY CREST Institute
Sentinel-2
What's Sentinel-2?
As mentioned earlier, it is like the Earth's instagram camera. Sentinel-2 takes super-detailed color pictures of Earth’s surface — tracking how plants grow, forests change, and farms flourish or dry out.
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What it can see?
Crop Tracker
Knows when crops are growing well or in trouble
How Is It Different from a Normal Camera?
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Sentinel-2 sees colors our eyes can’t.
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Like seeing in “plant vision.” It picks up infrared light which plants reflect when they’re healthy — and don’t when they’re sick.
How it Works (Raw Data Characteristics)
Sentinel-2 collects light reflecting off the Earth's surface. Just like our eyes see red, green, and blue, Sentinel-2 sees these plus many more "colors" in different parts of the light spectrum. These are its 13 spectral bands, each providing unique information:
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01
Blue, Green, Red (Bands 2, 3, 4)
These are the true color bands. When combined, they create images that look like what we see with our own eyes.
02
Red Edge (Bands 5, 6, 7)
These are very specific bands just beyond visible red light. They are incredibly sensitive to changes in plant health and can pick up early signs of plant stress or disease before visible damage appears.
03
NIR (Near Infrared - Band 8/8A)
This band is crucial for understanding plant health. Healthy vegetation strongly reflects near-infrared light, so a higher reflection in this band generally means healthier plants. It's also used for water body mapping (water absorbs NIR).
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SWIR (Short-Wave Infrared - Bands 11, 12)
These bands are excellent for detecting moisture content in plants and soil, and for mapping burn scars after fires. They can tell us if land is wet, dry, or has been affected by burning.
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Other Bands (e.g., Coastal Aerosol, Water Vapor, Cirrus)
These additional bands are used primarily for atmospheric correction and cloud detection, helping to ensure the clarity and accuracy of the land surface data.
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Spatial Resolution
This is how small of an area each pixel represents. Sentinel-2 captures data at different resolutions (10m, 20m, and 60m), giving it excellent detail for various applications.
What we Get (Data Products)
Data Products are the finished photo albums or recipe books that contain the above ingredients mentioned in different forms, ready for use.
The raw light measurements above are processed into clear, usable images:
Level-1C (L1C) Products (Top-Of-Atmosphere)
These are like a raw photo directly from the camera, before much editing. They contain the spectral reflectance measured at the top of the atmosphere, with data for each of the 13 bands (Blue, Green, Red, Red Edge, NIR, SWIR, etc.).
They are geometrically corrected (straightened out) and orthorectified (aligned to a map).
They are delivered in tiles (100km x 100km), with separate files for each spectral band.
Level-2A (L2A) Products (Bottom-Of-Atmosphere)
These are like a professionally edited photo. Atmospheric effects (like haze and clouds) have been largely removed, giving you a clearer picture of the spectral reflectance of the Earth's actual surface for all 13 bands.
These are the most commonly used products for applications like vegetation monitoring and land classification.
From these multiple spectral bands, you can calculate Vegetation Indices (like NDVI, which shows how green and healthy plants are by combining Red and NIR bands), Water Indices, and easily create detailed land use maps.
