In 2016, the USGS reorganized the Landsat archive into a tiered collection. This structure ensures that Landsat Level-1 products provide a consistent archive of known data quality to support time-series analyses and data “stacking”, while controlling continuous improvement of the archive and access to all data as they are acquired.
The Collection definition consists of three categories: Tier 1, Tier 2, and Real-Time. Data in Tier 1 meet formal geometric and radiometric quality criteria. Tier 2 do not meet the Tier 1 criteria. The Real-Time Tier contains data immediately after acquisitions that use estimated parameters. Real-Time data are reprocessed and assessed for inclusion into Tier 1 or Tier 2 as soon as final parameters are available.
The implementation of Collections represents a significant change in the management of the Landsat Archive by ensuring consistent quality through time and across instruments, along with additional changes like metadata and file names.
Future Landsat Collection releases will be carefully planned and paced to bring timely improvements without imposing too frequent changes on the Landsat user community. For example, a centerpiece in Collection 2 will be improved geodetic accuracy using updated Landsat 8 Operational Land Imager (OLI) ground control points and/or the Sentinel 2 Global Reference Image (GRI). In addition, the USGS will distrubute a Level-2 standard product suite that includes surface reflectance and surface temperature.
Landsat Collection 1 consists of Level-1 data products generated from Landsat 8 Operational Land Imager (OLI)/Thermal Infrared Sensor (TIRS), Landsat 7 Enhanced Thematic Mapper Plus (ETM+), Landsat 4-5 Thematic Mapper (TM), and Landsat 1-5 Multispectral Scanner (MSS) instruments. Collection 1 Level-2 and Level-3 Landsat Science Products inherit characteristics of the Landsat Collection 1 Level-1 data products.
Visit the Landsat Collection 1 web page for more information and documentation.