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An Approach for Estimating Soil Organic Matter Content Using Synthetic IRS Satellite Data in Tropical Soils of Lop Buri, Thailand With respect to SBS, the ANN chosen SOM-sensitive bands from laboratory-based spectrometer data (Daniel et al. 2002) were R410, R460, and R480. Equations 2, 3, and 4 were derived through multiple regression technique (where R2 > 0.90) from the available spectral (i.e., IRS compatible) data of 550 nm (Green-band), 650 nm (Red-band) and 815 nm (NIR-band). The relationships between the compatible and non-compatible IRS bands of Eq-2,3, and 4 were mimicked by the existing IRS bands to produce the synthetic IRS bands. From those synthetic bands, several indexes were quantified. The stepwise multiple regression of those indexes gave the SOM model (Eq-5). R410 nm = 1.1 + 0.2 (R815) +0.05 (R650) + 0.7 (R550) Eq-2 R460 nm = -0.5 + 0.21 (R815) -0.02 (R650) + 0.7 (R550) Eq-3 R480 nm = 0.04 + 0.1 (R815) -0.26 (R650) +1.08 (R550) Eq-4 SOM (%) = 89.2 – 4.9(R460) +0.08 (R410)2 + 0.05 (R480)2 - 43 (R410/(R460* R480)) + 475.5 (R460/ (R410* R480)) – 4.3 ((R480* R480)/R460)) –0.89 ((R410*R460)/ R480) + 29 - 405.2* ÖR460/(R410 * R 480) Eq-5 The SOM-sensitive synthetic IRS bands, R410 nm, R460 nm and R480 nm are implemented on a GIS platform, and are shown on Figure 3. Those cloned bands were first modeled from point data of each sampling site, and latter interpolated (with IDW) on the grid-formatted surfaces. The SOM predictive model (Eq-5) is implemented on the layer “predicted) which has more or less similar pattern with the “observed” layer of measured SOM layer. The predicted and the expected layers of SOM are in good agreement (R2 = 0.72).  Figure 3. SOM modeling from Synthetic IRS data and its comparison with measured point SOM layer |