Landsat Tiers are the inventory structure for Landsat Collection 1 Level-1 data products and are based on data quality and level of processing. All scenes in the Landsat archive are assigned to a Collection category. The purpose of Collection categories is to support rapid and easy identification of suitable scenes for time-series pixel level analysis. During Collection 1 reprocessing, all Landsat 7 ETM+ scenes in the USGS archive are assigned to a specific “Tier”. These data have well-characterized radiometric quality and are cross-calibrated among the different Landsat sensors.
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 georegistration of Tier 1 scenes will be consistent and within prescribed tolerances [<=12 m root mean square error (RMSE)]. All Tier 1 Landsat data can be considered consistent and inter-calibrated (regardless of sensor) across the full collection.
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 as 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.
Newly acquired L7 and L8 data require a period of evaluation and calibration adjustment after acquisition, which can vary from days to weeks. Newly acquired data are processed immediately based on preliminary calibration coefficients, assigned to the temporary Real-Time (RT) Tier, and made available for download. When definitive calibration information becomes available, RT scenes are reprocessed and assigned to the appropriate Tier 1 or Tier 2 category.
For Landsat 7, it will take about 26 days after acquisition for a Real-Time scene to be processed into either Tier 1 or Tier 2, due to the time needed to finalize calibration and bumper mode parameters.
For Landsat 8, in order to apply the updated Thermal Infrared Sensor (TIRS) line-of-sight model parameters, it will take about 14 to 16 days after acquisition for a Real-Time scene to be processed into either Tier 1 or Tier 2.
Tier 1: LE07_L1TP_016039_20040918_20160211_01_T1
Tier 2: LT04_L1GS_017036_19821115_20160315_01_T2