1. Monitoring of Rice Growth Using Polarimetric Scatterometer System
RSSJ 2009, Komaba Research Campus, May 21-22, 2009
Monitoring of Rice Growth Using Polarimetric Scatterometer System
Yihyun Kim1*, S.Young Hong1, Eunyoung Choe1 and Hoonyol Lee2
1 National Academy of Agricultural Science, 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

2. 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

3. Objective
To analyze scattering characteristics of paddy rice obtained from
polarimetric scatterometer system in
Relationship between backscattering coefficients in L, C, X-band
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

4. Radar Backscattering Measurement of a Paddy Rice Field using Multi-frequency (L, C and X) and Full-polarization (2007)
Study site
Construction of polarimetric scatterometer system (L, C, X-band)
Calculation of backscattering coefficients
Measurement of backscattering coefficient for L, C, X-band during rice growth stage
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.

5. Study site The size field : 660m2
Location : Experimental field at NAAS, Suwon, Korea
Testing varieties : Chuchoungbyeo
The size field : 660m2
The test site was located at a NAAS experimental field Suwon, Korea. The rice cultivar was a Japonica type, called Chuchoung. The size field was about 660m2

6. Dual Polarimetric Horn Antenna
Polarimetric scatterometer system
Consist of polarimetric scatterometer system
Dual Polarimetric Horn Antenna
Network Analyzer
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
L-band
C-band
X-band
Calibration kit

7. Dual polarimetric horn
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

8. 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

9. Temporal variations of backscattering coefficients in bands
Temporal variations of backscattering coefficients at polarization and
incident angle 30°~60° for the L-band
Incident angle: 30
Incident angle: 40
Heading
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.
Incident angle: 50
Incident angle: 60

10. Temporal variations of backscattering coefficients in bands
Temporal variations of backscattering coefficients at polarization and
incident angle 30°~60° for the C-band
Incident angle: 40
Incident angle: 30
heading
Incident angle: 50
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.
Incident angle: 60

11. Temporal variations of backscattering coefficients in bands
Temporal variations of backscattering coefficients at polarization and
incident angle 30°~60° for the X-band
Incident angle: 30
Incident angle: 40
heading
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.
Incident angle: 50
Incident angle: 60

12. Analysis of scattering characteristics in paddy rice by X-band automatic scatterometer system
(2008)
Construction of X-band automatic scatterometer system
Growth data collection
Measurement of backscattering coefficient for X-band during rice
growth stage
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.

13. X-band automatic scatterometer system
Construction of X-band automatic scatterometer system
Weather condition (such as precipitation, wind, humidity) negative effect

14. Specification of the automatic scatterometer system
X-Band
Center frequency
9.65GHz
Bandwidth
1GHz
Number of frequency points
1601
Wavelength
0.031m
Slant range resolution
0.15m
Antenna type
Dual polarimetric horn
Antenna gain
22.4dB
Polarization
HH, VV, HV, VH
Incident angle
45°
Measurement interval
1 per 10minutes

15. Growth data collection
Plant height, Fresh and dry weight, LAI
Collection interval : about 1 per a week
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

16. Temporal variations of backscattering coefficients in X-band
Temporal variations of backscattering coefficients at polarization and
incident angle 45° for the X-band
Incident angle: 45
2007
2008

17. Relationship between backscattering coefficients at L, C, X-band and rice growth parameters
( )
Relationship between backscattering in bands and plant parameters
during rice growth stage
Optimum condition between backscattering coefficients in bands and plant parameters

18. Relationship between backscattering coefficients in bands and rice growth parameters
Correlation between backscattering coefficients at L-band and plant variables VV HH HV
Incident
angle
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***
0.88*** 60
0.79**
0.84**
* : level of significance p<0.05
** : level of significance p<0.01
*** : level of significance p<0.001
Tfw : Total fresh weight, Tdw : Total dry weight

19. Relationship between backscattering coefficients in bands and rice growth parameters
Correlation 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*
0.85**
0.92***
0.90*** 30
0.82**
0.78**
0.86***
0.83**
0.84***
0.91*** 35
0.70*
0.68*
0.93***
0.84**
0.89***
0.88*** 40
0.38ns
0.55*
0.50*
0.95***
0.87*** 45
0.64*
0.56*
0.58* 50
0.76**
0.73**
0.94*** 55 60
0.44*
0.43*

20. Relationship between backscattering coefficients in bands and rice growth parameters
Correlation 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**

21. Relationship between backscattering coefficients in bands and rice growth parameters
Correlation between backscattering coefficients at bands and grain dry weight
L-band(2007)
C-band(2007)
X-band(2007)
X-band(2008)
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
0.70**
-0.30ns
-0.40* 40
0.61*
0.40*
0.66*
-0.22ns
-0.86***
0.78*
-0.36ns 45
0.75**
0.23ns
0.63*
-0.83**
-0.13ns
0.88***
0.39ns
0.58*
0.89***
0.21ns
0.44* 50
0.71*
-0.67*
0.29ns
-0.16ns
-0.52*
0.84**
0.55*
0.65* 55
-0.29ns
0.07ns
0.17ns
-0.77**
0.80**
0.70* 60
0.30ns
0.18ns
-0.10ns
0.67*
0.81**
0.74**
0.69*

22. Coefficient of determination
Optimum condition between backscattering coefficients in bands and plant
parametrs
Optimum condition
Plant parameters
Band
Polarization
Incident angle
Coefficient of determination
Plant height(cm)
C-band HV
45°
R2=0.90**
LAI HH
50°
R2=0.91**
Biomass(g/m2)
L-band
R2=0.93**
Grain
dry weight(g/m2)
X-band VV
R2=0.82**

23. Conclusions
Backscattering coefficients of rice crop were measured with ground-based
scatterometer
The temporal variations of the backscattering coefficients of the rice crop at L-, C-,
X-band with full polarization during rice growth period
VV-polarization backscattering coefficients higher than HH-polarization
backscattering coefficients in early rice growth stage
Relationships between backscattering coefficients and the plant parameters
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 was sensitive to grain maturity at near harvesting stage
Optimum condition between backscattering coefficients in bands and plant
parameters
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.

24. Thank you
RURAL DEVELOPMENT ADMINISTRATION (RDA)