Landsat Collection 2, the second major reprocessing effort on the Landsat archive, resulted in several data product improvements that applied advancements in data processing, algorithm development, and data access and distribution capabilities.
Landsat Collection 2 contains Level-1 data from Landsats 1-9, and Level-2 and Level-3 science products from Landsats 4-9.
A primary characteristic of Collection 2 is the substantial improvement in the absolute geolocation accuracy of the global ground reference dataset - which improves interoperability of the Landsat archive through time. Collection 2 also includes updated global digital elevation modeling sources and calibration and validation updates.
Collection 2 contains Landsat Level-1 data for all sensors since 1972. Global Level-2 surface reflectance and surface temperature scene-based products are available for Landsat data from 1982 to present. Landsat U.S. Analysis Ready Data (ARD) tiled products are available for the conterminous U.S. from 1982-present.
The USGS are the first recipients of the Committee on Earth Observation Satellites (CEOS) endorsement for Analysis Ready Data for Land (CARD4L) - compliant products for Landsat Collection 2 Level-2 products. This internationally recognized certification ensures that Landsat Collection 2 Level-2 products are more interoperable with other Earth observing platforms, such as Europe’s Sentinel-2 satellite, as they too work towards CARD4L-compliant products.
Visit the Landsat Data Access web page to discover how to search and download all Landsat products from USGS data portals.
Collection 2 Highlights
Below is a high-level summary of the main improvements for Collection 2. For a more detailed description of Collection 2 processing, geometric, and radiometric improvements please visit the Collection 2 Level-1 page or review the accompanying documentation.
Download this Quick Reference Guide that lists the calibration, data processing, metadata, and product differences between Landsat Collection 1 Level-1, Level-2 U.S. Analysis Ready Data (ARD), and Landsat Collection 2 products.
Improved Geometric Accuracy
Re-baselining the Landsat 8 OLI Ground Control Points (GCPs) to the European Space Agency Copernicus Sentinel-2 Global Reference Image (GRI) improves the interoperability of the global Landsat archive spatially and temporally. The January 2020: Phase 4 - Collection 2 section on the Landsat Ground Control Points webpage provides more information. A 2019 publication shows improved accuracy in ground control by deploying a triangulation method on a continent by continent basis.
Improved Digital Elevation Modeling
Several digital elevation model sources are used in the processing of Landsat Collection 2 Level-1 data. These sources, based on specific geographic regions, contribute to improved vertical accuracy in Collection 2 when compared to data processed in the past. Together, these sources are all known as the Landsat Collection 2 Digital Elevation Model (DEM). Landsat Collection 2 uses the 3-arc-second DEM sources shown on the map below. To learn more about the Landsat Collection 2 DEM, visit the Landsat Collection 2 Digital Elevation Model page.
Improved Radiometric Calibration
Landsat Collection 2 includes several radiometric calibration improvements for Landsat 5 Thematic Mapper (TM) and Landsat 8 Operational Land Imager (OLI) data, including a correction for the TIRS striping effect (See: Radiometric Accuracy Improvements).
Global Level-2 Science and Atmospheric Auxiliary Products
New for Collection 2 is the processing and distribution of Level-2 surface reflectance and surface temperature science products for Landsat 4-5 TM, Landsat 7 ETM+ and Landsat 8 OLI/TIRS. Level-2 products are generated from Collection 2 Level-1 inputs that meet the <76 degrees Solar Zenith Angle constraint and include the required auxiliary data inputs to generate a scientifically viable product. (Please note that Landsat 1-5 Level-2 MSS surface reflectance products will only become available upon the maturity of an operational atmospheric compensation algorithm which satisfies the USGS Landsat program requirements.) Landsat Collection 2 Atmospheric Auxiliary Data used in the processing of Collection 2 Level-2 products are available to download for users wanting to generate custom Level-2 products using the Collection 2 surface reflectance and surface temperature algorithms.
Consistent Quality Assessment Bands
Landsat Collection 2 Level-1 products are delivered with a Quality Assessment Band (QA_Pixel) and a Radiometric Saturation and Terrain Occlusion Quality Assessment Band (QA_RADSAT). Collection 2 Level-2 products will include the Level-1 QA bands as well as a surface reflectance aerosol QA Band (SR_QA_AEROSOL) and a surface temperature QA Band (ST_QA) to provide consistent QA information between products. The Landsat Collection 2 Quality Assessment Bands page provides more information about the QA bands. * In February 2021, an issue was been discovered in the Pixel QA ‘clear bit’ (bit 6) for Landsat 4-7 scenes over water. Please visit the Landsat Collection 2 Known Issues page for more details about this issue.
Updated and Consistent Metadata Files
There are several enhancements and changes between Collection 1 and Collection 2 Level-1 metadata. New to Collection 2 data is the addition of an extensible markup language (XML) to the already offered Material Library File (MTL) (Object Description Language-based) format file. The metadata files facilitate consistency, machine-to-machine scripting and rapid querying of the USGS Landsat archive. There are also changes to the metadata fields visible on EarthExplorer and its associated applications. The Landsat Collection 2 Metadata page describes changes to each and provides files displaying the changes.
Cloud Optimized File Format
Landsat Collection 2 Level-1 data and Level-2 products are delivered in a Cloud Optimized Georeferenced (COG) Tagged Image File Format. COGs are an extension of the current GeoTIFF file format which improves access to Geospatial datasets in a cloud-based environment by allowing users to request only the bands that they need. For additional information on the COG file format please review the Landsat Cloud Optimized GeoTIFF (COG) Data Format Control Book (DFCB).
Collection 2 Tiers
Landsat Collection Tiers are the inventory structure for Level-1 data products and are based on data quality and level of processing. The tier definition purpose is to support easier identification of suitable scenes for time-series pixel-level analysis, and provide temporary data that are processed immediately upon downlink to be dispensed quickly in emergency response situations with limited calibration.
Real-Time (RT): Newly-acquired Landsat 8 and Landsat 9 OLI/TIRS data are processed upon downlink but use initial TIRS line-of-sight model parameters (Landsat 8). These data are placed in the Real-Time tier and made available for download in less than 12 hours (4-6 hours typically). Once the data have been reprocessed updated refined TIRS parameters, the products are transitioned to either Tier 1 or Tier 2 and removed from the Real-Time tier. The transition delay from Real-Time to Tier 1 or Tier 2 is between 14 and 26 days. Follow-on processing details are described below.
- Landsat 8 TIRS data may not meet specifications for co-registration with OLI. TIRS line-of-sight model parameters are refined based on data acquired during biweekly calibration maneuvers and scenes are reprocessed within 14 to 16 days of acquisition and placed into either Tier 1 or Tier 2.
- Landsat 9 OLI and TIRS data are available in less than 12 hours (4-6 hours typically) for a Tier 1 or Tier 2 directly after processing.
Tier 1 (T1): Landsat scenes with the highest available data quality are placed into Tier 1 and are considered suitable for time-series analysis. Tier 1 includes Level-1 Precision and Terrain (L1TP) corrected data that have well-characterized radiometry and are inter-calibrated across the different Landsat instruments. The georegistration of Tier 1 scenes is consistent and within prescribed image-to-image tolerances of ≦ 12-meter radial root mean square error (RMSE).
Tier 2 (T2): Landsat scenes not meeting Tier 1 criteria during processing are assigned to Tier 2. Tier 2 scenes adhere to the same radiometric standard as Tier 1 scenes, but do not meet the Tier 1 geometry specification due to less accurate orbital information (specific to older Landsat sensors), significant cloud cover, insufficient ground control, or other factors. This includes Systematic Terrain (L1GT) and Systematic (L1GS) processed data. Users interested in Tier 2 scenes can query the RMSE and other properties to determine their application suitability.
The Tier designation (T1, T2, RT) is visible at the end of the Landsat Product Identifier, as shown in the examples below. It is also provided as an additional metadata field in EarthExplorer. Note: Historical Landsat 4-5 TM and Landsat 7 ETM+ data received from International Ground Stations supporting the Landsat Global Archive Consolidation effort are placed in either Tier 1 or Tier 2 after Collection 1 processing.
Tier 1: LC08_L1TP_013042_20211225_20211230_02_T1
Tier 2: LT05_L1GS_178058_19950410_20200912_02_T2
Landsat Collection 2 Known Issues
The Landsat Collection 2 Known Issues page provides information about artifacts found in Landsat Collection 2 data products, and attempts to make recommendations on how users can make corrections. Known issues relating to Landsat spacecrafts and/or instruments can be found on this Landsat Known Issues page. Note: Some issues originating from spacecrafts and/or instruments do affect Landsat data and products; please review both pages when data issues are discovered.
Landsat Collection 2 Reprocessing Events
Occasionally, select Landsat scenes must be reprocessed. The USGS recommends that users consider replacing any already downloaded Landsat data and subsequently derived products with newly reprocessed data products. Please note that when a scene is reprocessed, the Product Identifier is updated to reflect the most recent processing date.
Please visit the Collection 2 Reprocessing Events page to learn more about what scenes have been reprocessed.
Visit the Landsat Data Access web page to discover how to search and download all Landsat products from USGS data portals. The USGS Landsat no-cost open access data policy remains intact since its inception in 2008.
Product Generation Time Frames
Landsat 8 OLI/TIRS Level-1 Real-Time scenes are available for download within 4-6 hours after acquisition.
Landsat Level-2 Surface Reflectance and Surface Temperature products are typically available within 24 hours after a scene has been processed into Tier 1 or Tier 2:
- For Landsat 8 OLI/TIRS, it takes approximately 4-11 days to process to a Tier 1 or Tier 2 product while refined TIRS instrument line of sight model parameters are applied to Real-Time scenes.
- Landsat 9 delivers Collection 2 Level-1 Tier 1 or Tier 2 scenes within 4-6 hours of acquisition, and a Level-2 Surface Reflectance and Surface Temperature product within 3 days of acquisition.
Please refer to the Landsat Collection 2 Product Generation Timeline (right) for a visual view of the timeframes described above.
Crawford, C.J., Roy, D.P., Arab, S., Barnes, C., Vermote, E., Hulley, G., Gerace, A., Choate, M., Engebretson, C., et al. 2023. “The 50-Year Landsat Collection 2 Archive.” Science of Remote Sensing (2023) https://doi.org/10.1016/j.srs.2023.100103.
Users are encouraged to reference the COG Data Format Control Book (DFCB) for a detailed description of the image, product and metadata files. Together with the instrument specific Level-1 DFCBs, the COG DFCB provides a comprehensive overview of the new Landsat Collection 2 products.
Collection 2 Level-1 Documents
- Landsat 8-9 OLI/TIRS Collection 2 Level 1 Data Format Control Book
- Landsat 7 ETM+ Collection 2 Level 1 Data Format Control Book
- Landsat 4-5 TM Collection 2 Level 1 Data Format Control Book
- Landsat 1-5 MSS Collection 2 Level 1 Data Format Control Book
Collection 2 Level-2 Documents
- Landsat 8-9 OLI/TIRS Collection 2 Level 2 Data Format Control Book
- Landsat 7 ETM+ Collection 2 Level 2 Data Format Control Book
- Landsat 4-5 TM Collection 2 Level 2 Data Format Control Book
- Landsat Atmospheric Auxiliary Data Format Control Book
- Landsat 8 Collection 2 Level 2 Science Product Guide
- Landsat 4-7 Collection 2 Level 2 Science Product Guide
Summary of Enhancement and Improvements
A summary of the enhancements and improvements between Collection 1 and Collection 2 is provided in this quick reference guide.