Landsat Geometry

Landsat Levels of Processing

All Landsat Level-1 data products are created using the best available processing level for each particular scene. The processing level used is determined by the existence of ground control points (GCP), elevation data provided by a Digital Elevation Model (DEM), and/or data collected by the spacecraft and sensor (Payload Correction Data - PCD). 

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Landsat scenes are processed to a Level-1 precision and terrain corrected product (L1TP) if possible. In the case of insufficient reference data, a systematic and terrain corrected L1GT or a systematic L1GS product will be created instead.

L1GT products are created when the systematic product has consistent and sufficient locational accuracy to permit the application of a terrain model.

L1GS products are created when the locational accuracy is not sufficient to apply terrain correction, such as:  

  1. Insufficient number of ground control points, such as small islands or Antarctic
  2. Opaque clouds that obscure the ground
  3. Locational errors greater than the search distance for ground control

Precision and Terrain Correction (Level-1TP, L1TP)

Precision and Terrain Correction provides radiometric and geodetic accuracy by incorporating ground control points while employing a Digital Elevation Model (DEM) for topographic displacement. Geodetic accuracy of the product depends on the image quality and the accuracy, number, and distribution of the ground control points (GCP):

  • Ground control points used for L1TP correction are currently based on the Global Land Survey (GLS) reference database. The reference database is being revised, using Landsat 8 Operational Land Imager (OLI) data within the GCP improvement plan.
  • The elevation data used for relief displacement of the L1TP data include Shuttle Radar Topography Mission (SRTM)Canadian Digital Elevation Data (CDED)Digital Terrain Elevation Data (DTED)Global 30 Arc-Second Elevation (GTOPO30), and Greenland Ice Mapping Project (GIMP) source DEMs.
  • Precision fit and verification RMSE estimates are only available for L1TP products. The precision fit estimate (RMSE_Model) quantifies how well the control points used in the precision registration match the reference GCP database. The verification estimate (RMSE_Verify) of MSS and TM data quantifies how well the image matches an independent set of GCPs in the reference GCP database.
  • The specification for L1TP product acceptance varies by sensor. The specification is rigid for Landsat 8, Landsat 7, and Landsat 4-5 Thematic Mapper (TM) data, many of which have excellent internal geometry. Given the poor internal geometry of the Multispectral Sensor (MSS) aboard Landsat 1-5, the use of ground control even for data with large RMSE was considered preferable, to creating a large proportion of data as L1GS with the internal geometry uncorrected. 
  • The information provided in the metadata file can be used to evaluate the geodetic accuracy of the L1TP data product.

Systematic Terrain Correction (Level-1GT, L1GT)

Systematic Terrain Correction provides systematic, radiometric, and geometric accuracy, while employing a Digital Elevation Model (DEM) to correct for relief displacement:

  • Landsat 7 scenes without sufficient control to produce L1TP images are processed to an L1GT.
  • Landsat 8 scenes without sufficient ground point control to produce L1TP products are processed as L1GT. The accuracy of the L1GT systematic product approaches that of an L1TP product. Registration to the shared Ground Control Point reference data set improves the co-registration to the other Landsat sensors. For scenes where the reference database error exceeds 30 meters, the L1GT images will have better absolute accuracy than Landsat 8 L1TP data, but may not be co-registered to within 30 meters.
  • Landsat 7 and Landsat 8 data over Antarctica are processed to an L1GT, since it has not been possible to generate ground control in Antarctica suitable for the generation of an L1TP product. The Radarsat Antarctic Mapping Project Digital Elevation Model Version 2 (RAMP V2 DEM) is the terrain correction source for Antarctica.

Systematic Correction (Level-1GS, L1GS)

Systematic Correction provides systematic radiometric and geometric corrections, which are derived from data collected by the sensor and spacecraft.

  • Landsat scenes processed as L1GS do not have sufficient geodetic accuracy to include in image-to-image analysis without further image-specific evaluation and registration.
  • Landsat ETM+ geometric accuracy of the systematically corrected product should be within 125 meters 90 percent of the time for low-relief areas at sea level based on pre-fit estimates.  Error increases as distance and elevation increase from low relief areas.
  • Landsat TM geometric accuracy for L1GS products should be within 700 meters, 90 percent of the time for low-relief areas at sea level based on pre-fit estimates.
  • Landsat MSS geometric accuracy for L1GS products is substantially worse than later sensors. Both the internal geometry and locational accuracy will require manual registration of the images
  • Landsat TM and MSS images may be offset from its correct spatial location by thousands of meters, preventing the use of terrain correction for systematic products.

The success rate for creating L1TP products varies by sensor, but also by cloud cover. The table below displays each cloud-cover class and lists the proportion of images that process to an L1TP, those that fallback to an L1GT or L1GS after a failed attempt to produce an L1TP (clouds or poor ephemeris data), and the proportion that are planned to produce an L1GT (night, Antarctica or insufficient land features). These values were generated from the most recent Landsat Product Generation System (LPGS) software version.

Landsat Level-1 Products Registration Success by Cloud Cover

Landsat Level-1 Products Registration Success by Cloud Cover, based on values generated February 28, 2019. 

Table Explanation
*Landsat 1-7: All path/row combinations are separated internally into two groups; path/rows that will undergo precision and terrain correction, and path/rows that will not be precision and terrain corrected. If precision and terrain correction is attempted and successful, the scene becomes an L1TP. If precision correction is unsuccessful, the scene becomes an L1GT FB (fallback). If precision and terrain correction is not applied, the scene will become an L1GS (or L1GT for Landsat 7).
*Landsat 8: All path/rows are separated into two groups; path/rows that have produced at least one L1TP scene, and path/rows that have never produced an L1TP scene. Precision and terrain correction is attempted on all Landsat 8 scenes.  If precision correction fails from the path/row group that has produced at least one L1TP, the scene becomes an L1GT FB (fallback). If precision correction fails from a path/row that has never produced an L1TP (which is likely), then the scene will become an L1GT (no fallback).

RMSE Distribution Plots

The distribution of the RMSE for each sensor shows significant improvement as sensor and spacecraft technologies evolve, as of February 28, 2019.

Landsat 8 OLI Collection 1 L1TP RMSE

Landsat 8 OLI Collection 1 L1TP RMSE: Equal to or less than 12 meters in 92.2 percent of the data. 

Landsat 7 ETM+ Collection 1 L1TP RMSE

Landsat 7 ETM+ Collection 1 L1TP RMSE: Equal to or less than 12 meters in 96.3 percent of the data. 

Landsat 4-5 TM Collection 1 L1TP RMSE

Landsat 4-5 TM Collection 1 L1TP RMSE: Equal to or less than 12 meters in 95.4 percent of the data. 

Landsat 1-5 MSS Pre-Collection L1T RMSE

Landsat 1-5 MSS Collection 1 L1T RMSE: Less than 12 meters in 1.23 percent of the data.