Data continuity validation of Landsat 7 ETM+ and Landsat 8 OLI based on vegetation indices

摘要

Landsat satellites series provide large amounts of data for both the regional and global vegetation time series observation. As the currently operational Landsat satellites, Landsat 7 and Landsat 8 take the responsibility of multi-decadal Landsat imagery. However, the updating or changing of Landsat sensors will bring in a certain degree of bias for the long-term continuity research. To minimize this bias between ETM+ on board Landsat 7 and OLI on board Landsat 8, we intended to obtain the relationship between these two sensors for further research based on long-term Landsat data. Firstly, the wheat reflectance spectra from the field experiments was used to simulate for ETM+ and OLI satellite-based values. Then the linear regression relationship between two sensors was established via three vegetation indices which were the Normalized Difference Vegetation Index (NDVI), Soil-adjusted Vegetation Index (SAVI) and Enhanced Vegetation Index (EVI). Lastly, three study areas (A: Harvard Forest, B: Hulun Buir Grassland and C: Kahurangi National Park in New Zealand) were selected to verify the performance of the regression relationships by using images of ETM+ and OLI for the closed available time period. The results showed that: (1) the values of OLI was l%-3% higher than ETM+ when only the instruments setting difference was been taken into consideration. (2) the continuity between the two Landsat sensors improved averaging 3% after the calibration by the regression relationship. Thus, the results based on regression relationship of this records offer the potential of effective calibration for the Landsat time series research related to ETM+ and OLI sensors.