During the summer of 2016, the USGS has made changes to manage the Landsat archive as a tiered Collection of Landsat data. A Collection will provide a stable environmental record. If significant radiometric or geometric changes are required, all data will be reprocessed and a new Collection will be released. The tiered structure clearly identifies the subset of the Landsat archive that meets radiometric and geometric criteria suitable for time series analysis and the creation of data stacks/cubes, while continuing to provide access to the entire Landsat archive.
Starting with Collection 1, every Landsat 4-5 (L4-5) Thematic Mapper (TM), Landsat 7 (L7) Enhanced Thematic Mapper Plus (ETM+), and Landsat 8 (L8) Operational Land Imager (OLI)/Thermal Infrared Sensor (TIRS) scene is assigned to a specific tier. There are many changes being implemented to Landsat Level-1 data products to support this effort, including new Landsat Product Identifiers, “Collection” and “Tier” designations, metadata changes, and additional supporting files included with Level-1 data products. Higher level products will inherit characteristics of the Level-1 data products.
Collection 1 Tiers
Landsat Tiers are the inventory structure for Landsat Collection 1 Level-1 data products and are based on data quality and level of processing. The purpose of the tier definition is to (1) support rapid and easy identification of suitable scenes for time-series pixel level analysis and (2) provide a holding zone for real-time data prior to the availability of definitive calibration information.
Landsat scenes with the highest available data quality are placed into Tier 1 and are considered suitable for time-series processing analysis. Tier 1 includes Level-1 Precision Terrain (L1TP) processed data that have well-characterized radiometry and are inter-calibrated across the different Landsat sensors. The geo-registration of Tier 1 scenes will be consistent and within prescribed tolerances [≤12m radial root mean square error (RMSE)].
Landsat scenes not meeting Tier 1 criteria during processing are assigned to Tier 2. This includes Systematic Terrain (L1GT) and Systematic (L1GS) processed scenes, as well any L1TP scenes that do not meet the Tier 1 specifications due to significant cloud cover, insufficient ground control, and other factors. Users interested in Tier 2 scenes can analyze the RMSE and other properties to determine the suitability for use in individual applications and studies.
New Landsat Product Identifiers
The Scene ID will remain in the metadata file (MTL.txt) delivered with the Level-1 data product. The heritage Scene ID will also be visible and searchable (along with the new Collection 1 Landsat Product ID) in the online metadata on EarthExplorer.
Processing Level Designation Changes