Abstract
Abstract. A PRELIMINARY INVESTIGATION ON COMPARISON AND TRANSFORMATION OF SENTINEL-2 MSI AND LANDSAT 8 OLI Timely and accurate earth observation with short revisit interval is usually necessary, especially for emergency response. Currently, several new generation sensors provided with similar channel characteristics have been operated onboard different satellite platforms, including Sentinel-2 and Landsat 8. Joint use of the observations by different sensors offers an opportunity to meet the demands for emergency requirements. For example, through the combination of Landsat and Sentinel-2 data, the land can be observed every 2–3 days at medium spatial resolution. However, differences are expected in radiometric values (e.g., channel reflectance) of the corresponding channels between two sensors. Spectral response function (SRF) is taken as an important aspect of sensor settings. Accordingly, between-sensor differences due to SRFs variation need to be quantified and compensated. The comparison of SRFs shows difference (more or less) in channel settings between Sentinel-2 Multi-Spectral Instrument (MSI) and Landsat 8 Operational Land Imager (OLI). Effect of the difference in SRF on corresponding values between MSI and OLI was investigated, mainly in terms of channel reflectance and several derived spectral indices. Spectra samples from ASTER Spectral Library Version 2.0 and Hyperion data archives were used in obtaining channel reflectance simulation of MSI and OLI. Preliminary results show that MSI and OLI are well comparable in several channels with small relative discrepancy (< 5 %), including the Costal Aerosol channel, a NIR (855–875 nm) channel, the SWIR channels, and the Cirrus channel. Meanwhile, for channels covering Blue, Green, Red, and NIR (785–900 nm), the between-sensor differences are significantly presented. Compared with the difference in reflectance of each individual channel, the difference in derived spectral index is more significant. In addition, effectiveness of linear transformation model is not ensured when the target belongs to another spectra collection. If an improper transformation model is selected, the between-sensor discrepancy will even largely increase. In conclusion, improvement in between-sensor consistency is possibly a challenge, through linear transformation based on model(s) generated from other spectra collections.
Highlights
For some special event, meaningful information available to users is necessarily required
The Multi-Spectral Instrument (MSI) imagery consists of 13 spectral channels, from the visible and the near-infrared (VNIR) to the shortwave infrared (SWIR) at suitable spatial resolutions
The Operational Land Imager (OLI) imagery consists of 9 spectral channels, of which 8 multispectral channels are provided with a spatial resolution of 30 meters and a panchromatic channel with a spatial resolution of 15 meters (Figure 1 and Table 1)
Summary
For some special event (i.e., monitoring and assessment for emergency risk), meaningful information available to users is necessarily required This service relies on timely and accurate earth observation with short revisit interval. Several new generation sensors with similar channel characteristics have been operated onboard different satellites, including Sentinel-2 and Landsat 8. Joint use of the observations obtained from different sensors may offer an opportunity to meet the demands for emergency requirements. The Landsat program has been collecting space-based imagery with moderate spatial resolution of the Earth’s surface since the launch of its first member (Landsat 1) in 1972. Free accessibility of the observations from Sentinel-2 MSI and Landsat 8 OLI shows obvious advantage in the joint use of these data in terms of application, data quality and spatial resolution. Previous findings suggest that the effect of differences due to SRFs of the sensors need to be quantified and compensated to avoid large uncertainties in cross-calibration results (Chander et al, 2013)
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