Important Information: Upcoming Landsat Data Processing Changes
During Spring 2015, significant changes to Landsat products will improve the consistency of Landsat 1-8 data records. These changes will enhance data usability.
The planned changes, potential impacts, and benefits are summarized below. Future Landsat Updates will be published to provide more details on each of these changes.
Landsat 1-7 MSS, TM, and ETM+
- Quality Assessment (QA) Band for Landsat 1-7 products. The new QA band will provide information for detecting clouds, cloud shadows, snow/ice, and water in TM and ETM+ products, compatible with the updated Landsat 8 OLI/TIRS QA band. The new QA band for Landsat MSS will only include values for fill, non-cloudy, and cloudy pixels.
- New Cloud Cover Assessment (CCA) algorithm to populate the QA band. The CFMask will be implemented as the primary algorithm for calculation of clouds, cloud shadows, snow/ice, and water in TM and ETM+ products.
- New information added to the metadata (MTL.txt) file. Additions include consistent incorporation of fields describing CCA and fields needed to calculate scene center-based Top-of-Atmosphere (TOA) reflectance:
- Cloud Cover Assessment score using the CFmask algorithm
- Land Cloud Cover Assessment scores
- Earth-Sun Distance constant
- Scaling constants for MSS, TM, and ETM+ TOA reflectance
- Thermal constants needed to calculate TM and ETM+ TOA brightness temperature
The name of the Landsat MSS cloud cover parameter was changed to match the TM, ETM+, and OLI/TIRS naming convention, which may affect existing automated processes. The additional parameters will enable other automated processes.
- Landsat 4-5 TM National Land Archive Production System (NLAPS) format data will be processed in Landsat Product Generation System (LPGS). A number of scenes in the archive could not be processed through LPGS due to formatting and calibration differences resulting from NLAPS processing . Upcoming system modifications will enable those scenes to be processed in LPGS, effectively making almost 12,000 “new” scenes available to the user community.
Landsat 8 OLI and TIRS
- New Angle Coefficient File added to Level-1 data product. Per-pixel solar illumination and sensor view angles will be delivered as an additional file within the Level-1 data product. The solar illumination angle coefficients in the Angle Coefficient File can be used in place of the scene-center solar zenith, in combination with the Scaling and Thermal constants to calculate per-pixel TOA reflectance and brightness temperature.
- New Cloud Cover Assessment (CCA) algorithm to populate the QA band. The CFMask will be implemented as the primary algorithm for calculation of clouds, cloud shadows, snow/ice, and water. The existing CCA algorithms will remain in the processing flow if the input needed to run CFmask is not available.
- Land-Based Cloud Cover. Using QA Band information, the percentage of land pixels affected by clouds will be calculated and written to the metadata file (MTL.txt) as a scene-based score.
- Additional Quality Image for Landsat TM and ETM+. The new QA Band in Landsat MSS, TM, and ETM+ data will be added to LandsatLook. The Quality image for TM and ETM+ will be a colored 8-bit .png, as is currently offered for Landsat 8. Landsat MSS Quality images will have fewer categories.
- New stretch for the Thermal Band image. The LandsatLook Thermal Band .jpg is currently stretched with a scene-specific two percent clip. In order to facilitate mosaicking and to permit comparison of images, a constant stretch will be applied to all thermal images.