Blockiness Artifact in Landsat Collection 2 Surface Temperature Products

By Landsat Missions

The Landsat Collection 2 (C2) Level-2 Surface Temperature (ST) product may appear ‘blocky’ over small surface targets.

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This artifact traces back to the Landsat emissivity (EMIS) band, which is derived from the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Emissivity Dataset (ASTER GED) Version 3 (GEDv3) emissivity data as well as ASTER Normalized Difference Vegetation Index (NDVI). The ASTER GED native resolution is 100-meters (m), so interpolation onto a finer resolution of 30-m will appear blocky. The nearest neighbor (NN) method currently used for resampling emissivity in Landsat C2 ST amplifies the blocky appearance. For additional information about the Landsat emissivity calculation procedure, see Section 4.7.5.4.4. of the Landsat 8-9 Calibration Validation Algorithm Description Document.

Example of blockiness artifact in Landsat Collection 2 Level-2 Surface Temperature Image — These images display (Left) an RGB composite of a Level-1 Top of Atmosphere (TOA) reflectance, and (Right) the corresponding Level-2 Surface Temperature Band 10 image. The blockiness artifact that has been found in Landsat Collection 2 Level-2 Surface Temperature images can be seen in the southern portion of the center-pivot irrigation circles. Scene Product ID: LC08_L2SP_041032_20210706_20210713_02_T1

The NDVI data from ASTER visible and near infrared (VNIR) bands are registered to the thermal infrared data. Given the limited geolocation accuracy of the TIR camera on ASTER, the visual blocky artifact in Landsat C2 ST is more noticeable in locations where a geometric mis-registration exists between the ASTER NDVI and Landsat data. For additional information about the geometric accuracy of ASTER, see the ASTER User Handbook.

Please note that the native resolution of Landsat thermal infrared data is coarser than 30-m (100-m for Landsat 8-9 TIRS, 60-m for Landsat 7 ETM+, and 120-m for Landsat 4-5 TM). The Level-1 thermal radiances are artificially interpolated onto a 30-m grid. Therefore, the blocky artifact in Level-2 ST does not cause any information loss. Users are encouraged to utilize the Landsat C2 ST uncertainty band (ST_QA) to exclude pixels with high uncertainty from analysis.

The USGS will likely consider updated emissivity sources and smoother resampling techniques (e.g., bilinear or bicubic interpolation) for future release of the Landsat Surface Temperature products.

Users are encouraged to contact USGS Customer Services with additional issues discovered or questions about the Collection 2 Landsat ST product.