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A refined empirical line approach for reflectance factor retrieval from Landsat-5 TM and Landsat-7 ETM+
- Moran, M.S., Bryant, R., Thome, K., Ni, W., Nouvellon, Y., Gonzalez-Dugo, M.P., Qi, J., Clarke, T.R.
- Remote sensing of environment 2001 v.78 no.1-2 pp. 71
- agricultural land, semiarid zones, rangelands, remote sensing, Landsat, reflectance, image analysis, Arizona
- The recent launch of Landsat-7 ETM+ extends the uninterrupted stream of TM and ETM+ images to a potential span of 32 years. This exceptional image set will allow long-term studies of natural resources, but will require an operational method for converting image digital number (dn) to the temporally comparable surface reflectance factor (ρsλ). A refinement to the empirical line (EL) approach for reflectance factor retrieval (RFR) from the Landsat-5 and -7 TM and ETM+ has been proposed. The refined empirical line (REL) approach requires only one within-scene calibration target, minimal field measurements of that target, and a reasonable estimate of dn for ρsλ=0 using a radiative transfer model or values provided by this analysis. This study showed that the REL approach worked well for a 10-year Landsat-5 TM and Landsat-7 ETM+ image set in Arizona and ρsλ was retrieved with an estimated accuracy of 0.01. A quantitative approach was proposed to determine the suitability of a within-scene target for the REL approach, and based on historical measurements, a variety of targets met the size and brightness requirements for the REL approach. This operational approach for RFR should encourage long-term investigations of natural resources to answer critical questions regarding resource management and effects of climate changes.