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1 Korean Journal of Remote Sensing, Vol.25, No.1, 2009, pp.31~44 Estimation of Paddy Rice Growth Parameters Using L, C, X-bands Polarimetric Scatterometer Yi-Hyun Kim*, Suk-Young Hong*, and Hoonyol Lee** *National Academy of Agricultural Science, Rural Development Administration **Department of Geophysics, Kangwon National University Abstract : The objective of this study was to measure backscattering coefficients of paddy rice using a L-, C-, and X-band scatterometer system with full polarization and various angles during the rice growth period and to relate backscattering coefficients to rice growth parameters. Radar backscattering measurements of paddy rice field using multifrequency (L, C, and X) and full polarization were conducted at an experimental field located in National Academy of Agricultural Science (NAAS), Suwon, Korea. The scatterometer system consists of dual-polarimetric square horn antennas, HP8720D vector network analyzer (20 MHz ~ 20 GHz), RF cables, and a personal computer that controls frequency, polarization and data storage. The backscattering coefficients were calculated by applying radar equation for the measured at incidence angles between 20 and 60 with 5 interval for four polarization (HH, VV, HV, VH), respectively. We measured the temporal variations of backscattering coefficients of the rice crop at L-, C-, X-band during a rice growth period. In three bands, VV-polarized backscattering coefficients were higher than hh-polarized backscattering coefficients during rooting stage (mid-june) and HH-polarized backscattering coefficients were higher than VV-, HV/VH-polarized backscattering coefficients after panicle initiation stage (mid-july). Cross polarized backscattering coefficients in X-band increased towards the heading stage (mid-aug) and thereafter saturated, again increased near the harvesting season. Backscattering coefficients of range at X-band were lower than that of L-, C-band. HH-, VV-polarized s steadily increased toward panicle initiation stage and thereafter decreased, and again increased near the harvesting season. We plotted the relationship between backscattering coefficients with L-, C-, X-band and rice growth parameters. Biomass was correlated with L-band hh-polarization at a large incident angle. LAI (Leaf Area Index) was highly correlated with C-band HH- and cross-polarizations. Grain weight was correlated with backscattering coefficients of X-band VV-polarization at a large incidence angle. X-band was sensitive to grain maturity during the post heading stage. Key Words : Backscattering coefficients, Full polarization, L-band, C-band, X-band, Rice growth, Biomass, LAI. hoonyol@kangwon.ac.kr 31

2 Korean Journal of Remote Sensing, Vol.25, No.1, 2009 s 32

3 Estimation of Paddy Rice Growth Parameters Using L, C, X-bands Polarimetric Scatterometer Fig. 1. Consist of polarimetric scatterometer system. 33

4 Korean Journal of Remote Sensing, Vol.25, No.1, 2009 Table 1. Specification of the scatterometer system Specification L-Band C-Band X-Band Center frequency 1.27 GHz 5.3 GHz 9.65 GHz Bandwidth 0.12 GHz 0.6 GHz 1 GHz Number of frequency points Antenna type Dual polarimetric horn Dual polarimetric horn Dual polarimetric horn Antenna gain 12.4 db 20.1 db 22.4 db Polarization HH, VV, HV, VH HH, VV, HV, VH HH, VV, HV, VH Incident angle 20 ~ ~ ~ 60 Platform height 4.16 m 4.16 m 4.16 m P r P t G t G r l 2 P r = s (1) (4p) 3 R 4 P t G t G r l s R s A s 0 s = (2) A Z i = a i e jfi (3) 34

5 Estimation of Paddy Rice Growth Parameters Using L, C, X-bands Polarimetric Scatterometer a f 8 1 Z = S (a i cosf i + ja i sinf i ) (4) 8 i=1 U P t P r 2 U 2 V = ( r ) V t = (5) s P 10 log( ) [ ] = 20 log U = 10 log G t G r l 2 r s (6) P (4p) 3 R 4 t \s(db) = 10 log s = 20 log U _ G t (db) _ G r (db) _ 20 log l + 30 log 4p + 40 log R G t G r A DR A = l (7) cosq i DR DR = c/2b q i l R q R q L _ band : s (db) = 20logU+21.35(dB)+30logR+10log cosq i C _ band : s (db) = 20logU+30.27(dB)+30logR+10log cosq i X _ band : s (db) = 20logU+32.21(dB)+30logR+10log cosq i P r P t 35

6 Korean Journal of Remote Sensing, Vol.25, No.1, 2009 (a) Incident angle : 30 (b) Incident angle : 40 (c) Incident angle : 50 (d) Incident angle : 60 Fig. 2. Temporal variations of backscattering coefficients at polarization and incident angle 30 ~ 60 for the L-band. (a) Incident angle : 30 (b) Incident angle : 40 (c) Incident angle : 50 (d) Incident angle : 60 Fig. 3. Temporal variations of backscattering coefficients at polarization and incident angle 30 ~ 60 for the C-band. 36

7 Estimation of Paddy Rice Growth Parameters Using L, C, X-bands Polarimetric Scatterometer (a) Incident angle : 30 (b) Incident angle : 40 (c) Incident angle : 50 (d) Incident angle : 60 Fig. 4. Temporal variations of backscattering coefficients at polarization and incident angle 30 ~ 60 for the X-band. Fig. 5. Temporal variation in rice plant height. Fig. 6. Temporal variation in rice Leaf Area Index. 37

8 Korean Journal of Remote Sensing, Vol.25, No.1, 2009 Fig. 7. Temporal variation in rice fresh weight. Fig. 8. Temporal variation in rice grain dry weight. Table 2. Correlation coefficients between backscattering coefficients and rice growth parameters at L-band VV HH VV HV HH HV Incident Plant LAI Tfw Tdw Plant LAI Tfw Tdw Plant LAI Tfw Tdw Incident angle height LAI (g/m Tfw 2 ) (g/m Tdw 2 ) (g/m Tfw 2 ) (g/m Tdw 2 ) (g/m Tfw 2 ) (g/m Tdw 2 ) angle (g/m 2 ) (g/m 2 height LAI ) (g/m 2 ) (g/m 2 height LAI (cm) (cm) ) (cm) (g/m 2 ) (g/m 2 ) *** -0.81** -0.90*** -0.87*** -0.56* ns ns ns 0.21 ns 0.38 ns 0.29 ns 0.32 ns * ns ns ns 0.24 ns 0.44* 0.38 ns 0.38 ns 0.76** 0.85** 0.81** 0.81** ns 0.28 ns 0.15 ns 0.18 ns ns ns -0.42* ns 0.91*** 0.77** 0.85** 0.82** * -0.63* -0.58* -0.62* 0.40 ns 0.25 ns 0.31 ns 0.28 ns 0.89*** 0.71** 0.80** 0.78** ** 0.58* 0.70* 0.68* 0.74** 0.73** 0.76** 0.72** 0.89*** 0.81** 0.86*** 0.85** *** 0.78** 0.87*** 0.85** 0.94*** 0.89*** 0.92*** 0.91*** 0.90*** 0.91*** 0.90*** 0.86*** *** 0.63* 0.75** 0.73** 0.94*** 0.91*** 0.97*** 0.98*** 0.92*** 0.86*** 0.90*** 0.89*** ** 0.62* 0.75** 0.73** 0.93*** 0.90*** 0.93*** 0.91*** 0.90*** 0.88*** 0.92*** 0.92*** *** 0.74** 0.81** 0.79** 0.86*** 0.88*** 0.89*** 0.87*** 0.84** 0.90*** 0.91*** 0.91*** Tfw : Total fresh weight, Tdw : Total dry weight ns : Non significance * : level of significance p<0.05 ** : level of significance p<0.01 *** : level of significance p<

9 Estimation of Paddy Rice Growth Parameters Using L, C, X-bands Polarimetric Scatterometer Table 3. Correlation coefficients between backscattering coefficients and rice growth parameters at C-band VV HH VV HV HH HV Incident Plant LAI Tfw Tdw Plant LAI Tfw Tdw Plant LAI Tfw Tdw Incident angle height LAI (g/m Tfw 2 ) (g/m Tdw 2 ) (g/m Tfw 2 ) (g/m Tdw 2 ) (g/m Tfw 2 ) (g/m Tdw 2 ) angle (g/m 2 ) (g/m 2 height LAI ) (g/m 2 ) (g/m 2 height LAI (cm) (cm) ) (cm) (g/m 2 ) (g/m 2 ) *** -0.74** -0.84** -0.83** -0.84** -0.67* -0.76** -0.75** 0.81** 0.67* 0.74** 0.71** ** 0.72** 0.75** 0.74** 0.48* 0.48* 0.46* 0.48* 0.85** 0.92*** 0.90*** 0.90*** ** 0.78** 0.82** 0.81** 0.86*** 0.83** 0.84** 0.85** 0.83** 0.92*** 0.91*** 0.92*** * 0.70* 0.67* 0.68* 0.93*** 0.84** 0.90*** 0.89*** 0.88*** 0.91*** 0.89*** 0.88*** ns 0.55* 0.50* 0.50* 0.95*** 0.87*** 0.92*** 0.91*** 0.91*** 0.92*** 0.88*** 0.87*** ns 0.64* 0.56* 0.58* 0.90*** 0.91*** 0.93*** 0.93*** 0.95*** 0.88*** 0.90*** 0.87*** * 0.76** 0.74** 0.73** 0.94*** 0.95*** 0.93*** 0.93*** 0.90*** 0.85** 0.88*** 0.87*** * 0.70* 0.68* 0.67* 0.93*** 0.90*** 0.92*** 0.92*** 0.88*** 0.83** 0.86*** 0.84** ns 0.46* 0.44* 0.43* 0.92*** 0.92*** 0.91*** 0.92*** 0.91*** 0.83** 0.88*** 0.86*** * Tfw : Total fresh weight, Tdw : Total dry weight ns : Non significance * : level of significance p<0.05 ** : level of significance p<0.01 *** : level of significance p<0.001 Table 4. Correlation coefficients between backscattering coefficients and rice growth parameters at X-band VV HH VV HV HH HV Incident Plant LAI Tfw Tdw Plant LAI Tfw Tdw Plant LAI Tfw Tdw Incident angle height LAI (g/m Tfw 2 ) (g/m Tdw 2 ) (g/m Tfw 2 ) (g/m Tdw 2 ) (g/m Tfw 2 ) (g/m Tdw 2 ) angle (g/m 2 ) (g/m 2 height LAI ) (g/m 2 ) (g/m 2 height LAI (cm) (cm) ) (cm) (g/m 2 ) (g/m 2 ) ns 0.41* 0.32 ns 0.32 ns 0.68* 0.63* 0.64* 0.63* 0.80** 0.83** 0.82** 0.82** * 0.70* 0.68* 0.67* 0.72** 0.66* 0.68* 0.67* 0.73** 0.74** 0.74** 0.72** * 0.57* 0.54* 0.52* 0.82** 0.82** 0.84** 0.82** 0.65* 0.75** 0.70** 0.69** * 0.67* 0.62* 0.61* 0.81** 0.83** 0.80** 0.83** 0.71** 0.79** 0.74** 0.74** * 0.61* 0.55* 0.56* 0.72** 0.83** 0.79** 0.81** 0.67* 0.81** 0.74** 0.74** ns 0.45* 0.42* 0.40* 0.74** 0.80** 0.81** 0.82** 0.76** 0.81** 0.81** 0.79** ns 0.29 ns 0.28 ns 0.24 ns 0.71** 0.77** 0.75** 0.76** 0.74** 0.74** 0.76** 0.73** ns ns ns ns 0.75** 0.81** 0.80** 0.80** 0.82** 0.79** 0.83** 0.81** ns -0.44* ns -0.41* 0.75** 0.79** 0.79** 0.78** 0.81** 0.71** 0.77** 0.75** * Tfw : Total fresh weight, Tdw : Total dry weight ns : Non significance * : level of significance p<0.05 ** : level of significance p<0.01 *** : level of significance p<

10 Korean Journal of Remote Sensing, Vol.25, No.1, 2009 Table 5. Correlation coefficients between L-, C-, X-band backscattering coefficients and grain dry weight L-band C-band X-band L-band C-band X-band Incident angle VV HH HV VV VV HH HH HV HV VV VV HH HHHV HV *** -0.85** -0.64* -0.50* ns 0.26 ns -0.54* ns 0.10 ns *** -0.74** 0.06 ns ns ns -0.70* ns 0.35 ns 0.56* ** -0.64* 0.53* -0.55* ns -0.55* 0.51* 0.31 ns -0.45* * 0.72* 0.72* -0.81** ns 0.27 ns 0.70* ns -0.40* * 0.40* 0.66* ns -0.80** ns 0.78** ns -0.45* ** 0.23 ns 0.63* ns -0.78** ns 0.87*** 0.39 ns 0.58* * -0.67* 0.29 ns ns -0.52* 0.23 ns 0.83** 0.55* 0.65* * ns 0.07 ns 0.17 ns -0.77** 0.43* 0.80** 0.70* 0.71* ns 0.18 ns ns 0.67* -0.70* 0.51* 0.81** 0.74** 0.69* ns : Non significance * : level of significance p<0.05 ** : level of significance p<0.01 *** : level of significance p<0.001 Table 6. Optimum condition between backscattering coefficients at and rice growth parameters Band Polarization Incident angle Correlation coefficient (r) Plant height(cm) C-band HV 45 r=0.95*** LAI C-band HH 50 r=0.95*** Biomass(g/m 2 ) L-band HH 50 r=0.96*** Grain dry weight(g/m 2 ) X-band VV 45 r=0.87** ** : level of significance p<0.01 *** : level of significance p<0.001 y= x x R 2 =0.92*** (n=20) R 2 =0.92*** RMSE= (a) (b) Fig. 9. (a) Relationship between backscattering coefficient in C-band(VH, 45 ) and plant height during rice growth stage. (b) Relationship between Measured and estimated plant height during rice growth stage. 40

11 Estimation of Paddy Rice Growth Parameters Using L, C, X-bands Polarimetric Scatterometer y=0.0035x x R 2 =0.92*** (n=20) R 2 =0.91*** RMSE= (a) (b) Fig. 10. (a) Relationship between backscattering coefficient in C-band(HH, 50 ) and LAI during rice growth stage. (b) Relationship between Measured and estimated LAI during rice growth stage. y=0.5475x x R 2 =0.95*** (n=19) R 2 =0.94*** RMSE= (a) (b) Fig. 11. (a) Relationship between backscattering coefficient in L-band(HH, 50 ) and fresh weight during rice growth stage. (b) Relationship between Measured and estimated fresh weight during rice growth stage. 41

12 Korean Journal of Remote Sensing, Vol.25, No.1, 2009 y= x x R 2 =0.82** (n=8) R 2 =0.82*** RMSE= (a) Fig. 12. (a) Relationship between backscattering coefficient in X-band(VV, 45 ) and grain dry weight during rice growth stage. (b) Relationship between Measured and estimated grain dry weight during rice growth stage. (b) 42

13 Estimation of Paddy Rice Growth Parameters Using L, C, X-bands Polarimetric Scatterometer Anthony, F. and Stephen, L. Durden A threecomponent scattering model for polarimetric SAR data, Remote Sens. Environ, 36(3): Attema, E. P. and F. T. Ulaby, Vegetation modeled as a water cloud, Radio Science, 13: Bouman. B. A. M., Crop Parameter Estimation from Ground-Based X-Band (3-cm Wave) Radar backscattering Data, Remote Sens. Environ, 37: Brisco. B., R. J. Brown, J. A. Koehler., G. J. Sofko., and M. J. McKibben, The Diurnal Pattern of Microwave Backscattering by Wheat, Remote Sens. Environ, 34: Brisco, B. and R. J. Brown, Agricultural applications with radar, Chapter 7 in Principles & Applications of Imaging Radar, edited by F.M. Henderson and A.J. Lewis, Manual of Remote Sensing Vol.2, Wiley, Danvers, MA. pp Inoue, Y., T. Kurosu., H. Maeno, S. Uratsuka., T. Kowu., K. Dabrowska-Zielinska, and J. Qi, Season-long daily measurements of multifrequency (Ka, Ku, X, C, and L) and full-polarization backscatter signatures over paddy rice field and their relationship with biological variables, Remote Sensing of Environment, 81: Hong, S. Y., S. H. Hong, and S. K. Rim, Relationship between Radarsat backscattering coefficient and rice growth, Korean J. Remote Sensing, 16(2): Kim, S. B., Y. Kong, and Y. S. Kim, Radar backscattering measurements of rice crop using X-band scatterometer, IEEE Transactions on Geoscience and Remote Sensing, 38(3): Le, Toan, T. Ribbes. F. Wang, L. Floury, N. K. Ding, J. A. Kong, M. Fujita, and T. Kurosu, Rice crop mapping and monitoring using ERS-1 data based on experiment and modeling results, IEEE Transactions on Geoscience and Remote Sensing, 35: Macelloni, G., P. Palosica, R. Pampalori, F. Marliani, and M. Gai, The relationship between the backscattering coefficient and biomass of narrow and broad leaf crops, IEEE Transactions on Geoscience and Remote Sensing, 39(4): Macelloni, G., S. Palosica, P., and R. Pampalori, Modelling radar backscatter from crops during the growth cycle, Agronomie, 22: Moran, M. S., A. Vidal., D. Troufleau., Y. Inoue, and T. A. Mitchell, Ku- and C-band SAR for discriminating agricultural crop and soil conditions, IEEE Transactions on Geoscience and 43

14 Korean Journal of Remote Sensing, Vol.25, No.1, 2009 Remote Sensing, 36: Paloscica, S., An empirical approach to estimating leaf index from multifrequency SAR data, International Journal of Remote Sensing, 19(2): Paris, J. F., The effect of leaf size on the microwave backscattering by corn, Remote Sensing of Environment, 19: Prevot, L., I. Champion, and G. Guyot, Estimating surface soil moisture and leaf area index of a wheat canopy using a dualfrequency (C and X bands) scatterometer, Remote Sensing of Environment, 46: Ulaby, F. T., C. T., Allen, G. Eger, and E. T. Kanemasu, Relating the microwave backscattering coefficient to leaf area index, Remote Sensing of Environment, 14: Ulaby, F. T. and C. Elachi, Radar Polarimetry for Geoscience Applications, Artech House Inc. Wigneron, J. P., P. Ferrazzoli., A. Olioso., P. Bertuzzi, and A. Chanzy, A simple approach to monitor crop biomass from C-band radar data, Remote Sensing of Environment, 69: Yamaguchi, Y., T. Moriyama, M. Ishido, and H. Yamada, Four-component scattering model for polarimetric SAR image decomposition, IEEE Transactions on Geoscience and Remote Sensing, 43(8):

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09È«¼®¿µ5~152s Korean Journal of Remote Sensing, Vol.23, No.2, 2007, pp.45~52 Measurement of Backscattering Coefficients of Rice Canopy Using a Ground Polarimetric Scatterometer System Suk-Young Hong*, Jin-Young Hong**,