Radiometric processing levels

Processing is essential for transforming raw geospatial data into meaningful imagery. Processing levels act as a framework for understanding the level of transformation and manipulation the data has undergone. To select the right data for your use case, it’s important to understand the processing levels offered.

Optical imagery falls into four radiometric processing levels: basic, TOA, surface reflectance, and display.

Basic imagery is provided without any radiometric processing. The raw pixel values or digital numbers (DN) won’t be radiometrically calibrated but will undergo sensor correction to be consistent and comparable across the image.

Inclusions

Basic imagery is sensor-corrected to minimize sensor-to-sensor variation and sensor defects.

Exclusions

Basic imagery isn't radiometrically calibrated, and won't provide radiance or reflectance values.

Basic imagery provides close-to-raw values that are suited for advanced users to perform preliminary analysis and further processing.

Pléiades, Pléiades Neo, and SPOT basic imagery provides radiometric calibration coefficients to allow users to perform their own radiometric calibration.

Top-of-atmosphere (TOA) imagery is radiometrically calibrated. The pixel values represent the radiance or reflectance at the height of the sensor which may include atmospheric effects and inconsistent illumination.

Inclusions

TOA imagery is radiometrically calibrated and sensor-corrected.

Exclusions

TOA imagery isn't atmospherically corrected, and will contain atmospheric effects like scattering and absorption.

TOA imagery is more standardized and can be compared with TOA imagery from other sources. It’s suited for most geospatial analysis use cases.

Surface reflectance or bottom-of-atmosphere (BOA) imagery is atmospherically corrected. The pixel values represent the reflectance values from the Earth’s surface without systemic effects of the atmosphere and variations in solar illumination.

Inclusions

In addition to being radiometrically calibrated and sensor-corrected, surface reflectance imagery is atmospherically corrected.

Exclusions

Surface reflectance imagery will still contain clouds, pollution, and other atmospheric aerosols.

Surface reflectance imagery can be directly compared with data across different dates and sources. It’s suited for change detection, landcover classification, and vegetative analysis.

Display imagery is color-corrected to provide natural or true colors as seen by the human eye. The pixel values are typically reprojected to 8-bit, which makes them more visually appealing but doesn’t represent meaningful physical values.

Inclusions

In addition to being radiometrically calibrated, sensor and atmospherically corrected, display imagery is color-corrected.

Exclusions

Display imagery can't be converted back to the other radiometric processing levels.

It’s suited for visualization, communication, and image detection algorithms.

At least one radiometric processing level per collection is always available on the console, but the availability of other levels may differ depending on the collection. Some levels are only available upon request.

^*Upon request.