From Ocean Teacher Library
Remote Sensing Product LevelsContents |
Background
Satellite data are the subject of very complex and lengthy processing steps, in order to go from the raw data stream (in engineering units characteristic of the physical sensors on the satellite) to the attractive, global maps of selected parameters. The stages in the conversion process are known as product levels (or processing levels) and there is a more-or-less canonical terminology used by remote sensing agencies and scientists to identify them.
"Standard" Level Definitions
| Processing Levels | US NASA Definitions | WMO Definitions |
| Level 0 | Reconstructed, unprocessed data at full resolution; all communications artifacts have been removed | Raw data |
| Level 1 | Level 0 data that has been time-referenced and annotated with ancillary information, including radiometric and geometric calibration coefficients, and geolocation information | Data extracted by instrument, at full instrument pixel resolution, with Earth-location and calibration information |
| Level 2 | Derived geophysical variables at the same resolution and location as the Level 1 data | Geophysical value (temperature, humidity, radiative flux…) at instrument pixel resolution |
| Level 3 | Variables mapped on uniform space-time grids, usually with some completeness and consistency | Remapped (gridded) product based on geophysical value derived at instrument pixel resolution |
| Level 4 | Model output or results from analyses of lower level data | Composite product (multisource) or result of model analysis of lower level data |
The key word in the definition of Level 3 is "mapped" which indicates that the data have been analyzed from original XYZ form (in lower levels) to a regular grid (usually unprojected, equirectangular or "plate caree"). Software tools available for working with remote sensing imagery on PC/Windows platforms can almost always handle Level 3 products easily (for subsetting and or conversion to GIS-compatible formats). This is true of Level 4, also. Level 2, on the other hand, which usually involves swaths of data over the earth's surface, is a more difficult situation, depending on the specific formats provided. Levels 1 and 0 are highly resource- and labor-dependent, and not usually attempted by general-purpose ocean data centers.
Additional Resources
- Ocean Color Web products specifications - Definitions of product levels
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Information about this article
Short title: Product Levels
Description: none
Expertise level: beginner
Author: Murray.Brown
Approval status: approved
Approved by: Murray.Brown
Last change: 2009-9-10
Subsection of: Remote Sensing Data Concepts
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