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Landsat Update - Volume 9 Issue 3 2015

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Landsat Update - Volume 9 Issue 3 2015

Landsat 8 Data Processing Changes

New production code was released April 23, 2015 to enhance the usability of Landsat 8 products. Some of the planned changes were postponed in favor of coordinating new features in Landsat 8 with similar changes in Landsats 4-7 TM and ETM+ scheduled for the fall/winter of 2015. Other features expected to impact users have also been added since the last Landsat Update. The originally published information is in italics below, and modifications are noted in the UPDATE area of each section below.

Any questions or concerns about these changes can be directed to Landsat User Services: custserv@usgs.gov.

Changes Affecting Landsat 8 OLI and TIRS data

  1. New Angle Coefficient File added to Level-1 data product (01/28/2015). 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.

    UPDATE (02/27/2015): To clarify the above statement: Solar illumination and sensor view angles will not be provided; instead, a file containing parameters needed to calculate the angles and angle bands will be provided, along with a Linux tool to generate angle bands. The solar zenith angle band can be used in combination with rescaling factors from metadata to calculate per-pixel TOA reflectance. Thermal constants are needed to calculate brightness temperature.

    UPDATE (04/23/2015): The release of angle coefficient files and accompanying tool with Landsat 8 products has been postponed. A coordinated release of the files and tool is planned for Landsats 4-7 TM and ETM+ and Landsat 8 later this year.

  2. New Cloud Cover Assessment (CCA) algorithm to populate the QA band (01/28/2015). 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.

    UPDATE (02/27/2015): The Landsat 8 CFmask CCA algorithm has been removed from the upcoming release and will be included in a future release.

    UPDATE (04/23/2015): The Landsat 8 CFmask CCA algorithm release has been postponed. A coordinated release of the new algorithm is planned for Landsats 4-7 TM and ETM+ and Landsat 8 later this year.

  3. Land-Based Cloud Cover (01/28/2015). 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.

    UPDATE (02/27/2015): The land mask used to determine land pixels included in the Land CCA score is derived from NOAA's World Vector Shoreline dataset.

    UPDATE (04/23/2015): The new metadata field describing the percentage of cloud-covered land pixels now appears in the MTL as CLOUD_COVER_LAND.

  4. UPDATE Reprocessing zero-fill TIRS data (04/23/2015): The new release enables reprocessing for TIRS data acquired between December 19, 2014 and March 13, 2015, replacing the products that previously contained zero-fill TIRS bands. More reprocessing information is available in the April 16, 2015 Landsat Mission Headline, Landsat 8 Thermal Data Reprocessing Update.

  5. UPDATE SCENE_CENTER_TIME format change (04/23/2015): The SCENE_CENTER_TIME parameter in the MTL is now expressed in quotes, i.e., SCENE_CENTER_TIME = 18:29:23.3098165Z.

  6. UPDATE CCA score for night scenes (04/23/2015): Previous calculations of cloud cover for scenes with sun elevation angles less than or equal to zero (night) have been removed from processing. The CCA score now set to -1 for all night scenes.

  7. UPDATE No thermal constants in OLI-only scenes (04/23/2015): Functionality has been implemented to ensure that irrelevant thermal constants are not included in the MTL files when a scene does not contain TIRS data.

  8. UPDATE Precision of TIRS K1 and K2 constants (04/23/2015): The TIRS band-specific thermal conversion constants K1 and K2 in the MTL files are reported to 4 decimal places instead of 2 in this release.

  9. UPDATE Improved GCP accuracy (04/23/2015): Ground Control Point (GCP) handling has been enhanced to improve the location accuracy of Level-1T Standard Terrain Correction products at high latitudes.

Any questions or concerns about these changes can be directed to Landsat User Services: custserv@usgs.gov.

 

 

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