If you are a MODIS, AMSR-E or IceBridge data whiz, you may be familiar with the various processing levels for different data sets. Oftentimes the levels will be denoted as L1B or L2, etc. within the data set name. To the uninitiated it can be a challenge to understand what these levels really mean.
Data are processed at varying levels. The NASA Earth Observing System (EOS) define these levels as ranging from Level 0 to Level 4. Level 0 represents raw data, while Level 4 data have had the greatest amount of processing applied. At NSIDC, IceBridge data defined by the EOS system exist from Levels 0 to 3, while MODIS and AMSR-E data sets are offered at Level 2 and Level 3.
| Level | Definition |
| 0 | Unprocessed instrument data |
| 1A | Unprocessed instrument data alongside ancillary information |
| 1B | Data processed to sensor units, e.g. brightness temperatures |
| 2 | Derived geophysical variables, e.g. sea ice concentration |
| 3 | Variables that are mapped on a grid, e.g. data using EASE-Grid |
| 4 | Modeled output or variables derived from multiple measurements |
Many data sets offer a range of data levels, allowing users to choose the processing level that best fits their purposes. For more information, see the Earth Science Reference Handbook published by NASA EOS in 2006.
