(L, C and X) and Full-polarization IGARSS2008, Boston MA, July 6-11, 2008 Radar Backscattering Measurement of a Paddy Rice Field using Multi-frequency (L, C and X) and Full-polarization Yi-hyun Kim1*, S.Young Hong1 and Hoonyol Lee2 1 National Institute of Agricultural Science and Technology, RDA, Korea 2 Department of Geophysics, Kangwon National University, Korea Good afternoon My name is Yi-Hyun Kim from National Institute of Agricultural Science Technology in Korea My presentation title is radar backscattering measurement of a paddy rice field using multi-frequency(L, C and X) and full-polarization  

Contents 1 Background 2 Material and Methods 3 Results 4 Conclusion My presentation contents is following

Background Rice is one of the major crops in korea Microwave radar can penetrate cloud cover regardless of weather condition Ground-based polarimetric scatterometer has advantage of monitoring crop conditions with full polarization and various frequencies Plant parameters such as LAI, biomass, plant height are highly correlated with backscattering coefficients ENVISAT SAR data (5.3 GHz, hh-, hv-polarizations, and incidence angles between 28.5° and 40.9°) to monitor rice growth and compared the data with simulation results (Le Toan et al, 1997) RADARSAT data (5.3 GHz, hh-polarization, and incidence angles between 36° and 46°) was analyzed for monitoring the rice growth in Korea (Hong et al,2000) Rice is one of the major crops in Korea Microwave radar sensing has great potential, especially in monsoon Asia, since optical observations are often hampered by cloudy conditions Especially a ground-based polarimetric scatterometer has advantage of monitoring crop conditions continuously using full polarization and various frequencies Many plant parameters such as LAI, biomass, plant height are highly correlated with backscattering coefficients. According to frequency, polarization between plant parameters and backscattering coefficients was different For example last study work, Le Toan was study ENVISAT SAR data (5.3 GHz, hh-, hv-polarizations, and incidence angles between 28.5° and 40.9°) to monitor rice growth and compared the data with simulation results and Hong was study RADARSAT data (5.3 GHz, hh-polarization, and incidence angles between 36° and 46°) was analyzed for monitoring the rice growth in Korea

Objective To measure backscattering coefficients of paddy rice using L, C, X-bands scatterometer system during the growth period Relationship between backscattering coefficients and rice growth variables with full polarization and various angles We measure backscattering coefficients of paddy rice using L, C, X-bands scatterometer system during the growth period and investigate relationship between backscattering coefficients and rice growth variables for example plant height, Leaf Area Index, Biomass with full polarization and various angles

Study site - An experimental field at NIAST, Suwon, Korea The test site was located at a NIAST experimental field Suwon, Korea. The rice cultivar was a Japonica type, called Chuchung. The size field was about 660m2 Testing varieties : Chuchoungbyeo The size field : 660m2

Dual Polarimetric Horn Antenna Materials and Methods Consist of polarimetric scatterometer system Dual Polarimetric Horn Antenna Network Analyzer L-band C-band X-band Polarimetric scatterometer system consists of dual polarimetric horn antenna, vector network analyzer (VNA), RF cables, and a personal computer The system is calibrated using a calibration kit The VNA-based polarimetric scatterometer operates in a stepped-frequency sweep mode Polarimetric scatterometer provides a time domain radar return from a target as a fully polarimetric amplitude and phase data Calibration kit

Dual polarimetric horn Materials and Methods Specification of the scatterometer system Specification L-Band C-Band X-Band Center frequency 1.27GHz 5.3GHz 9.65GHz Bandwidth 0.12GHz 0.6GHz 1GHz Number of frequency points 201 801 1601 Antenna type Dual polarimetric horn Antenna gain 12.4dB 20.1dB 22.4dB Polarization HH, VV, HV, VH Incident angle 20°~60° Platform height 4.16m This system equipped with L, C, X-bands, and with full polarization The incident angles were between 20~60

Growth data collection - Plant height, Fresh and dry weight, LAI Transplant stage (mid-May) Panicle formation stage (mid-July) Heading stage (mid-Aug) Harvesting stage (mid-Oct) Growth data for the rice canopy, such as LAI, fresh and dry weight and plant height, were acquired at time of each scatterometer measurement simultaneously

Backscattering coefficients of each band the follow expression Calculation of backscattering coefficients (apply to radar equation) Backscattering coefficients were calculated by applying radar equation. It defined as the following expression. Backscattering coefficients of each band were calculated as the follow expressions. Backscattering coefficients of each band the follow expression

Polarimetric scatterometer system

Results Temporal variations of backscattering coefficients at polarization and incident angle 30°~60° for the L-band Incident angle: 30 Incident angle: 40 Heading heading Incident angle: 50 Incident angle: 60 Radar backscattering measurements were about 5 months from before transplantation of the rice seedings to harvest of the mature rice crop. This figure shows the temporal variations of the backscattering coefficients of the rice crop at L-band after transplanting, at various incidence angles. Backscattering coefficients of paddy fields at L-band ranged from were about -55dB ~ 0dB. VV-polarized backscattering coefficients higher than hh- and hv/vh-polarized backscattering coefficients during rooting stage.  Cross polarized backscattering coefficients increased towards the heading stage (mid-Aug) and thereafter saturated, again increased near the harvesting season.

Results Temporal variations of backscattering coefficients at polarization and incident angle 30°~60° for the C-band Incident angle: 30 Incident angle: 40 heading Incident angle: 50 Incident angle: 60 This figure shows changes of backscattering coefficients at C-band during the growing period. The HH-polarized backscattering coefficients at all incident angles (except 20°) increased as growth advanced and saturate at the ripening stage.

Results Temporal variations of backscattering coefficients at polarization and incident angle 30°~60° for the X-band Incident angle: 30 Incident angle: 40 Heading heading Incident angle: 50 Incident angle: 60 This figure shows change in backscattering coefficients at X-band with growth   Backscattering coefficients of range at X-band lower than that of L-, C-band. HH-, VV-polarized σ° steadily increased toward panicle initiation stage and thereafter decreased, and again increased near the harvesting season. This dual-peak trend was clearer larger incident angles. Larger incident angles (over 50°) at cross-polarized σ° showed similar phenomena.   Fresh weight was decreased and heads of the canopy were easily show, so X-band as high frequency sensitive to heading or grain maturity after heading stage.

Results Relationship between backscattering coefficients at L-band and plant variables VV HH HV Incidentangle Plant height LAI Tfw (g/m2) Tdw 20 -0.93*** -0.81** -0.90*** -0.87*** -0.56* -0.20ns -0.37ns -0.32ns 0.21ns 0.38ns 0.29ns 0.32ns 25 -0.53* 0.24ns 0.44* 0.76** 0.85** 0.81** 30 -0.01ns 0.28ns 0.15ns 0.18ns -0.39ns -0.38ns -0.42* -0.40ns 0.91*** 0.77** 0.82** 35 -0.49* -0.63* -0.58* -0.62* 0.40ns 0.25ns 0.31ns 0.89*** 0.71** 0.80** 0.78** 40 0.58* 0.70* 0.68* 0.74** 0.73** 0.72** 0.86*** 45 0.92*** 0.87*** 0.94*** 0.90*** 50 0.63* 0.75** 0.97*** 0.98*** 55 0.62* 0.93*** 0.95*** 0.88*** 60 0.79** We conducted a correlation analysis between the backscattering coefficients from each band and plant variables such as LAI and biomass This table shows relationship between backscattering coefficients in L-band and rice growth parameters The highest correlation coefficients for LAI were found at the 50° with HH-polarization The VV polarization showed weak correlated with LAI the HH- and cross-polarization Biomass was highly correlated with larger than 50° of incident angles with hh and cross-polarization.

Results Relationship between backscattering coefficients at C-band and plant variables VV HH HV Incident angle Plant height LAI Tfw (g/m2) Tdw 20 -0.94*** -0.74*** -0.84** -0.83** -0.67* -0.76** -0.75** 0.81** 0.67* 0.74** 0.71** 25 0.72** 0.75** 0.48* 0.46* 0.96*** 0.92*** 0.95*** 30 0.82** 0.78** 0.86*** 0.83** 0.84*** 0.85** 0.94*** 35 0.70* 0.68* 0.93*** 0.84** 0.90*** 0.89*** 0.91*** 40 0.38ns 0.55* 0.50* 0.87*** 45 0.64* 0.56* 0.58* 0.88*** 50 0.76** 0.73** 55 60 0.44* 0.43* This table shows correlation coefficients between backscattering coefficients in C-band with plant variables. LAI was highly correlated with the C-band HH- and cross-polarization at incident angle over 45°

Results Relationship between backscattering coefficients at X-band and plant variables VV HH HV Incident angle Plant height LAI Tfw (g/m2) Tdw 20 0.26ns 0.41* 0.32ns 0.68* 0.63* 0.64* 0.80** 0.83** 0.82** 25 0.62* 0.70* 0.67* 0.72** 0.66* 0.73** 0.74** 30 0.46* 0.57* 0.54* 0.52* 0.84** 0.65* 0.75** 0.70** 0.69** 35 0.50* 0.61* 0.81** 0.86*** 0.85** 0.71** 0.79** 40 0.43* 0.55* 0.56* 45 0.33ns 0.45* 0.42* 0.40* 0.76** 50 0.23ns 0.29ns 0.28ns 0.24ns 0.77* 55 -0.10ns -0.20ns -0.13ns -0.18ns 60 -0.25ns -0.44* -0.36ns -0.41* 0.78** 0.77** This table shows relationship between backscattering coefficients in X-band and rice growth parameters X-band is weakly correlated with mass information of the whole canopy such as LAI, biomass at incident angles

Results Correlation between L-, C-, X-band backscattering coefficients and grain dry weight L-band C-band X-band Incident angle VV HH HV 20 -0.96*** -0.85** -0.64* -0.50* -0.19ns 0.26ns -0.54* -0.05ns 0.10ns 25 -0.97*** -0.74** 0.06ns -0.39ns -0.70* -0.33ns 0.35ns 0.56* 30 -0.78** 0.53* -0.55* -0.38ns 0.51* 0.31ns -0.45* 35 0.43* 0.72* -0.81** -0.32ns 0.27ns 0.60* -0.30ns -0.40* 40 0.61* 0.40* 0.66* -0.22ns -0.86*** 0.64* -0.36ns 45 0.75** 0.23ns 0.63* -0.83** -0.13ns 0.78** 0.39ns 0.45* 50 0.71* -0.67* 0.29ns -0.16ns -0.52* 0.93*** 0.55* 0.81** 55 0.58* -0.29ns 0.07ns 0.17ns -0.77** 0.89*** 0.70* 0.87*** 60 0.30ns 0.18ns -0.10ns 0.67* 0.88*** 0.74** This figures shows correlation analysis between backscattering coefficients in L-, C-, X-band and grain weight. X band backscattering coefficients close correlation with the grain weight (ultimately the grain yield). The highest correlations for each band were VV polarization at incident angle 50° (r=0.93) at X-band. Backscattering coefficients at 55° and 60° of incident angles with VV-polarization were also highly correlated with grain weight. Contrarily, other bands were weakly correlated with the grain weight at all incident angles (except L-VV, 45°). Rice head (upper surface of the canopy) is the major scattering for high-frequency microwaves.

Conclusions The temporal variations of the backscattering coefficients of the rice crop at L-, C-, X-band during rice growth period VV-polarized backscattering coefficients higher than hh-polarized backscattering coefficients in early rice growth stage HH-polarized backscattering coefficients higher than vv-polarized backscattering coefficients after panicle initiation stage Biomass was correlated with L-band HH-polarization at large incident angle LAI was highly correlated with the C-band HH- and cross-polarizations X-band were weakly correlated with LAI and biomass Grain weight was correlated with backscattering coefficient with X-band (at larger angle, vv-polarization) In conclusion Backscattering coefficients of rice crop were measured with a ground-based scatterometer. The measurement was carried out at L-, C-, and X-band with full polarizations and different incident angles. The temporal variations of the backscattering coefficients of the rice crop at L-, C-, and X-band during a rice growth period. At larger incident angles, range of backscattering coefficients were higher than that of small incident angle. VV polarization backscattering coefficients were higher than HH-polarized backscattering coefficients in early rice growth stage. We conducted the relationship between backscattering coefficients with L-, C-, and X-band and rice growth parameters. Biomass was correlated with L-band hh-polarization at a larger incident angle. LAI was highly correlated with C band hh- and cross-polarizations. Grain weight was correlated with backscattering coefficients with X-band VV polarization at a larger incidence angle. X-band was sensitive to grain maturity at near harvesting season.

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