Abstract
The new Landsat-8 Operational Land Imager (OLI) is intended to be broadly compatible with the previous Landsat-7 Enhanced Thematic Mapper Plus (ETM+). The spectral response of the OLI is slightly different to the ETM+, and so there may be slight differences in the reflectance measurements. Since the differences are a function not just of spectral responses, but also of the target pixels, there is a need to assess these differences in practice, using imagery from the area of interest. This paper presents a large scale study of the differences between ETM+ and OLI in the Australian landscape. The analysis is carried out in terms of both top-of-atmosphere and surface reflectance, and also in terms of biophysical parameters modelled from those respective reflectance spectra. The results show small differences between the sensors, which can be magnified by modelling to a biophysical parameter. It is also shown that a part of this difference appears to be systematic, and can be reliably removed by regression equations to predict ETM+ reflectance from OLI reflectance, before applying biophysical models. This is important when models have been fitted to historical field data coincident with ETM+ imagery. However, there will remain a small per-pixel difference which could be an unwanted source of variability.
Highlights
The Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper (ETM+) instruments, aboard the Landsat series of satellites, have been observing the land surface since the launch of Landsat-4 in 1982
They show some scatter on the plots, and the orthogonal distance regression (ODR) slope values show that there is a systematic overall difference between the two instruments, this is much stronger in some bands than others
This means that the continuity between ETM+ and Operational Land Imager (OLI) is much better when dealing with surface reflectance
Summary
The Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper (ETM+) instruments, aboard the Landsat series of satellites, have been observing the land surface since the launch of Landsat-4 in 1982. Landsat-5 was launched in 1984, carrying an identical TM instrument, and Landsat-7 was launched in 1999, carrying the successor ETM+ instrument. These provide a broadly continuous record of satellite images of the land surface in six reflective wavelength bands, at a ground resolution of 30 m. Provide a review of the continuity issues between these two instruments. Markham and Helder [2] provide a comprehensive review of efforts to create a radiometrically consistent calibration of all the Landsat instruments
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