Imagery Processing Decision Tables

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Information for users to decide what imagery processing stretch and bit depth options are most appropriate for varying purposes.

Imagery Stretch & Bit Depth Outline

  Byte (8-bit integer) UInt16 (16-bit integer) Float32 (32-bit Decimal)
No stretch (ns)

Not Applicable

Terrain Corrected with digital number (DN) values 

Not Applicable 

Reflectance (rf)

Optimized image contrast over snow and ice surfaces

Comparative analysis between multiple images or cross-sensor imagery

Spectral response analysis

Modified reflectance (mr)

Optimized image contrast in temperate or tropical regions

Not Applicable

Not Applicable

Radiance (rd)

Not Applicable

Not Applicable

Use in atmosphere correction model

Imagery Stretch & Bit Depth Use Cases

Purpose

UInt16
ns
Byte
rf
Byte
mr
UInt16
rf
Float32
rf
Float32
rd
Comparison & analysis between multi-temporal images
Visual interpretation of snow/ice regions (Antarctica/Greenland) ⚫¹
Visual interpretation of diverse land cover (nonpolar/vegetation) ⚫¹-²
Full 11-bit radiometric depth
Reflectance values (TOA) ⚪³ ⚪³  
Radiance values (absolute)
Original digital number values (no radiometric calibration)
Has an absolute unit   Percent reflectance scaled to 200 N/A Percent reflectance scaled to 2000 Percent reflectance w/m²/str

▬  not recommended              ⚪  appropriate                   ⚫  optimal

¹ – 8-bit rasters are rendered faster than 16 or 32 bit data.  A GIS does not have to apply a histogram stretch to take 11 to 32 bits of data and render them in 8-bit.  However, radiometric detail in shadows or very bright areas may be lost in reducing the data to 8 bit.

² – Modified reflectance is based on reflectance, but shifted to enhance darker pixels.  It’s useful to make non-ice-covered areas bright enough interpret, but pixel values are not a valid percent reflectance value.

³ – Reflectance values scaled to fit into an integer package.

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