Standard Landsat 8 data products provided by the USGS EROS Center consist of quantized and calibrated scaled Digital Numbers (DN) representing multispectral image data acquired by both the Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS). The products are delivered in 16-bit unsigned integer format and can be rescaled to the Top Of Atmosphere (TOA) reflectance and/or radiance using radiometric rescaling coefficients provided in the product metadata file (MTL file), as briefly described below. The MTL file also contains the thermal constants needed to convert TIRS data to the top of atmosphere brightness temperature.
While the TIRS bands were designed to allow the use of split-window surface temperature retrieval algorithms, (such as the use of split window techniques for atmospheric correction and retrieval of surface temperature values), it is recommended that users refrain from relying on band 11 data in quantitative analysis of the TIRS data due to the larger calibration uncertainty associated with this band.
Conversion to TOA Radiance
Since the launch of Landsat 8 in 2013, thermal energy from outside the normal field of view (stray light) has affected the data collected in TIRS Bands 10 and 11. This varies throughout each scene and depends upon radiance outside the instrument field of view, which users cannot correct in the Landsat Level-1 data product. Band 11 is significantly more contaminated by stray light than Band 10. It is recommended that users refrain from using Band 11 data in quantitative analysis including use of Band 11 in split-wind surface temperature retrieval algorithms. Details about Landsat 8 TIRS stray light can be found in Appendix A of the
OLI and TIRS band data can be converted to TOA spectral radiance using the radiance rescaling factors provided in the metadata file
Conversion to Top of Atmosphere Brightness Temperature
TIRS band data can be converted from spectral radiance to top of atmosphere brightness temperature using the thermal constants provided in the metadata file
Now we are ready to convert the At-Satellite Brightness Temperature to Land Surface Temperature, using the following equation.
3) Conversion from At-Satellite Temperature to Land Surface Temperature
0 Comments