Landsat Missions

Landsat Collections

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During the summer of 2016, the USGS began making 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

New Landsat Product Identifiers

Additional Data Changes Applied During Collection 1 Processing

Collection 1 Processing Timeline

Sample Data Products

Changes to EarthExplorer

Documentation

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 availability of definitive calibration information.

Tier 1

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 [≤12m radial root mean square error (RMSE)].

Tier 2

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.

Real-Time (Temporary designation)

Newly acquired L7 and L8 data require a period of evaluation and calibration adjustment after acquisition, but 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. The Landsat Product Identifier correctly reflects the new category. The details about the follow-on processing for both L7 and L8 are described below. After the follow-on processing is complete and the data is available as Tier 1 or Tier 2, the Real-Time data is removed.

  • L8 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 updated within a few weeks of acquisition.
  • L7 ETM+ acquisitions are processed immediately using predicted ephemeris and initial bumper mode parameters and placed into the Real-Time tier. Shortly after initial processing (about 1 day), the data are processed again using definitive ephemeris, but still remain in the RT tier. During a period of instrument trending/characterization (about 26 days), calibration parameter adjustments finalize the geometric correction model, and the data are reprocessed and placed into the appropriate T1 or T2 tier, and the RT data is removed.

The Tier designation 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.

Tier 1:
Tier 2:
Real-Time:
LE07_L1TP_016039_20040918_20160211_01_T1
LT04_L1GS_017036_19821115_20160315_01_T2
LE07_L1GT_037035_20160314_20160314_01_RT

 

 

 

During Collection 1 processing, every L4-5 TM, L7 ETM+, and L8 OLI/TIRS scene is assigned to a specific “Tier”. All Landsat data are cross-calibrated (regardless of sensor) across the full collection. New L4-5 TM data acquired from international archives will be immediately placed in either T1 or T2. New L7 ETM+ and L8 OLI/TIRS will initially be placed in the Real-Time Tier. The wait time prior to assignment to T1 or T2 is on average 2 weeks with a maximum approaching 25 days.

New Landsat Product Identifiers

Along with information inherited from the Scene ID, the new Landsat Product Identifier also includes the updated processing levels, processing date, collection number, and collection category (noted in red in the graphic below).

Landsat Product Identifier

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.

Additional Data Changes Applied During Collection 1 Processing

Along with the new Landsat Product Identifier, new files and additions to metadata are also being implemented and delivered with the Level-1 data products.

New Files included in Level-1 data products

Additional Metadata (MTL.txt) fields

New Cloud Cover Algorithm

  • The C Function of Mask (CFMask) algorithm identify fill, cloud, cloud confidence, cloud shadow, and snow/ice in Landsat 4-5, Landsat 7, and Landsat 8 scenes for representation in the Quality Assessment (QA) band.

Specific for Landsat 8 OLI/TIRS

Processing Level Designation Changes

The processing level designations will be changing in Collection 1 Level-1 data products. The table below displays the levels currently used compared to those being implemented for Collection 1 data products.

Landsat Level-1 Processing Levels

Calibration Parameter File (CPF) Name Changes

Calibration Parameter Files (CPF) provide radiometric and geometric coefficients needed for processing of raw, uncorrected Landsat image data. Each timeframe specific CPF contains calibration coefficients that have been adjusted to correct for the time varying performance of the sensor.

The Collection 1 CPF file name includes the Collection number to uniquely link CPFs to specific Collections. During the transition to a new Collections, two CPFs will be maintained.

Pre-Collection:
Collection 1:
L7CPF20140401_20140630.03
LE07CPF_20140401_20140630_01.03

 

 

LXSSCPF_YYYYMMDD_yyyymmdd_CC.NN
L = Landsat (constant)
X = Sensor (“C” = OLI/TIRS Combined, “E” = ETM+, “T” = TM, “M”= MSS)
SS = Satellite (e.g. “07” = Landsat 7, “08” = Landsat 8)
CPF = Three-letter CPF designator
YYYYMMDD = Effective Starting Date (YYYY) / Month (MM) / Day (DD)
yyyymmdd = Effective Ending Date (yyyy) / Month (mm) / Day (dd)
CC = Collection number (“01”,”02”)
NN = Version Number for this file (starts with 00)

Response Linearization Look Up Tables (RLUT) Name Changes (Landsat 8 only)

RLUTs are additional files that accompany Calibration Parameter Files (CPF) and contain a mapping look up table to linearize the output of the OLI and TIRS detectors.   Like the CPF file names, the Collection RLUT files will have a different naming convention to support Collections.

Pre-Collection:
Collection 1:
L8RLUT20130211_20431231v09.h5
LC08RLUT_20130211_20431231_01_09.h5

 

 

LXSSRLUT_YYYYMMDD_yyyymmdd_CC.NN
L = Landsat (constant)
X = Sensor (“C” = OLI/TIRS Combined, “E” = ETM+, “T” = TM, “M”= MSS)
SS = Satellite (e.g. “07” = Landsat 7, “08” = Landsat 8)
RLUT = Four-letter RLUT designator
YYYYMMDD = Effective Starting Date (YYYY) / Month (MM) / Day (DD)
yyyymmdd = Effective Ending Date (yyyy) / Month (mm) / Day (dd)
CC = Collection number (“01”,”02”)
NN = Version Number for this file (starts with 00)

Collection 1 Processing Timeline

In August 2016, processing began for L4-5 TM and L7 ETM+ scenes, and data starting becoming available at the end of September. Collection 1 processing began with the most recently acquired Landsat scenes and moved back through the archive. Scenes collected over the conterminous United States were processed first, followed by the rest of the globe. Landsat 4-5 TM and Landsat 7 ETM+ Collection 1 processing is expected to last until April 2017.

In February 2017, processing will begin for L8 OLI/TIRS scenes, with data to start becoming available in late February or early March 2017.  Landsat 8 OLI/TIRS Collection 1 processing will follow the same procedure as Landsat 4-5 TM and Landsat 7 ETM+ and processing is expected to last until June 2017.

Landsat 1-5 Multispectral Scanner (MSS) data will be considered after the TM, ETM+ and OLI/TIRS processing efforts have completed.

When Collection 1 processing begins, newly acquired Landsat 8 and Landsat 7 scenes will be processed into the Pre-Collection data sets, as well as the new Collection 1 data sets – using the parameters established for each.

Pre-Collection data sets will be retained for some time after each dataset is completely processed into Collection 1 (specific timeframe is yet to be determined). Announcements will be made to alert users when the data set has completed Collection 1 processing, and when we plan to remove the Pre-Collection data sets.

Sample Data Products

Landsat 8 Collection 1 sample Level-1 data are listed below.

Landsat 8 OLI/TIRS Combined - .tar.gz (919 MB)
Landsat 8 OLI-Only - .tar.gz (820 MB)
Landsat 8 TIRS-Only - .tar.gz (92 MB)

Higher Level Science data products (such as Surface Reflectance and Spectral Indices) will be added when they become available.

Changes to EarthExplorer

Initially, Collection 1 Level-1 data products will be available only on EarthExplorer (EE). (Changes to USGS Global Visualization Viewer (GloVis) and LandsatLook Viewer are planned.)

The EE Data Set tab will clearly display Collection 1 and Pre-Collection data sets, as shown in the graphic below. Changes include consolidating the Pre-Collection data sets below for Collection 1:

  • Landsat 8 OLI/TIRS and Landsat 8 OLI/TIRS Pre-WRS-2 will combine to become L8 OLI/TIRS
  • Landsat 7 ETM+ SLC-on and the Landsat 7 ETM+ SLC-off will combine to become L7 ETM+
     

EarthExplorer Data Sets

The Additional Criteria tab for each Collection 1 data set also allows users to select parameters for each Landsat sensor (i.e., Landsat 7 SLC-on/SLC-off, T1/T2/RT, or RMSE range).

Documentation

Collection Definition Document (coming soon)

About

Landsat represents the world's longest continuously acquired collection of space-based moderate-resolution land remote sensing data. Four decades of imagery provides a unique resource for those who work in agriculture, geology, forestry, regional planning, education, mapping, and global change research. Landsat images are also invaluable for emergency response and disaster relief.

 

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