Estimationg rice growth parameters using X-band scatterometer data

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

IGARSS2010, Honolulu Hawaii, July 25-30, 2010

Background1

2

3

4

Material and Methods

Results

Conclusion

Contents

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)

Background

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)

Backscattering coefficients from a ground scatterometer are often affected by weather condition the necessity of near-continuous automatic measurement has arisen by the experiment in 2007 (Kim et al, 2008)

Objective

To analyze scattering characteristics of paddy rice obtained from L, C, X-band automatic scatterometer system

Relationship between backscattering coefficients in L, C, X-band and plant parameters with full polarization

Prediction of rice growth parameters using backscattering coefficients in L, C, X-band

Study site - An experimental field at NAAS, Suwon, Korea

Testing varieties : Chuchoungbyeo The size field : 660m2

Materials and Methods

L, C, X-band automatic scatterometer system

Measurement Interval : 1 per 10 min-

utes

L-band

X-band C-band

Specification of the L, C, X-band automatic scatterometer system

Materials and Methods

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 typeDual polarimetric

hornDual polarimetric

hornDual polarimetric

horn

Antenna gain 12.4dB 20.1dB 22.4dB

Range resolution 1.25m 0.25m 0.15m

Wavelength 0.23m 0.056m 0.031m

Polarization HH, VV, HV, VH HH, VV, HV, VH HH, VV, HV, VH

Platform height 4.16m 4.16m 4.16m

Growth data collection - Leaf Area Index, Plant height, Fresh and Dry weight etc.

Transplant stage (mid-May) Panicle formation stage (mid-July)

Heading stage (mid-Aug) Harvesting stage (mid-Oct)

Radar backscattering measurement - Between before transplanting(17 May, 2009) and harvesting stage(12 Oct, 2009)

Calculation of backscattering coefficients2

3 4(4 )t t r

tP G GP

R

(apply to radar equation)

( ) 10 log 20log ( ) ( ) 20 log 30log 4 40logt rdB U G dB G dB R

2

3 410log 20log 10log

4t rr

t

GGp Up R

2

2 r r

t t

v pUv p

Backscattering coefficients of X-band the follow expression: ( ) 20log 21.35( ) 30log 10log cosL band dB U dB R i

: ( ) 20log 30.27( ) 30log 10log cosC band dB U dB R i

: ( ) 20log 32.21( ) 30log 10log cosX band dB U dB R i

Results Temporal variations in growth parameters during rice growth

0 10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

0

10

20

30

40

50

60

70

80

90

100

110

DAT(Day After Transplanting)

plan

h he

ight

(cm

)

0 10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

DAT(Day After Transplanting)

LAI

heading stage

<Plant height> <Leaf Area Index>

Results Temporal variations in growth parameters during rice growth

<Fresh biomass> <Dry biomass>

heading stage

0 10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

0

50

100

150

200

250

300

350

400

DAT(Day After Transplanting)

Fres

h bi

omas

s(g/

m2)

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 0

20

40

60

80

100

120

140

160

180

200

DAT(Day After Transplanting)

Dry

bio

mas

s(g/

m2)

Results Temporal variations of backscattering coefficients at polarization and incident angle 45° for the L-band

140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

VVVHHVHH

DOY(Day of year)

scat

t. co

eff.(d

B)

booting stage ~ heading stage (most active rice growth period)

Results Temporal variations of backscattering coefficients at polarization and incident angle 45° for the C-band

140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

VVVHHVHH

DOY(Day of year)

scat

t. co

eff.(d

B)

Results Temporal variations of backscattering coefficients at polarization and incident angle 45° for the X-band

140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

VVVHHVHH

DOY(Day of year)

scat

t. co

eff.(d

B)

Results

VV HH HVIncident

anglePlantheight LAI Tfw

(g/m2)Gdw

(g/m2)Plantheight LAI Tfw

(g/m2)Gdw

(g/m2)Plantheight LAI Tfw

(g/m2)Gdw

(g/m2)

45 0.60* 0.86** 0.75** -0.78** 0.70** 0.92*** 0.83** -0.83** 0.77** 0.91*** 0.89*** -0.72**

Relationship between backscattering coefficients at L, C, X-band and plant variables

VV HH HVIncident

anglePlant

Height LAI Tfw(g/m2)

Gdw(g/m2)

Plantheight LAI Tfw

(g/m2)Gdw

(g/m2)Plantheight LAI Tfw

(g/m2)Gdw

(g/m2)

45 0.80** 0.91*** 0.90*** -0.78** 0.89*** 0.98*** 0.96*** -0.74** 0.79** 0.93*** 0.89*** -0.62*

L-band

C-band

VV HH HVIncident

anglePlantheight LAI Tfw

(g/m2)Gdw

(g/m2)Plantheight LAI Tfw

(g/m2)Gdw

(g/m2)Plantheight LAI Tfw

(g/m2)Gdw

(g/m2)

45 0.63* 0.66* 0.73** 0.94*** 0.72** 0.72** 0.81** 0.84** 0.79** 0.68* 0.83** 0.70*

X-band

Results

Optimum condi-tion

Growth parametersBand Polarization R2

Plant height(cm) L-band HH R2=0.86***

Leaf Area Index L-band HH R2=0.96***

Fresh Biomass(g/m2)

Above ground L-band HH R2=0.94***

Grain X-band VV R2=0.91***

Grain dry weight(g/m2) X-band VV R2=0.94***

Optimum condition for estimation of rice growth parameters

Results Prediction of Leaf Area Index using backscattering coefficients(L-band, HH)

-35 -30 -25 -20 -15 -10 -5 0 0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

f(x) = 0.139635779049249 x + 4.59667258582913R² = 0.962407918401895

Backscattering coefficients(L-band, HH, dB)

LAI

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Measured LAI('08)

Pred

icte

d LA

I by

mod

elin

g('0

9)

y = 0.8739x + 0.4459

R2 = 0.95***

RMSE = 0.2346

Results Prediction of Biomass using backscattering coefficients (L-band, HH)

y = 1.0028x – 0.5471R2 = 0.95***

RMSE = 8.5412

-40 -35 -30 -25 -20 -15 -10 -5 00

50

100

150

200

250

300

350

400

f(x) = 12.0663660082307 x + 378.71782951327R² = 0.912876455225859

Backscattering coefficients(L-band, HH, dB)

Tota

l fre

sh w

eigh

t(g/m

2)

0 50 100 150 200 250 300 350 400 0

50

100

150

200

250

300

350

400

450

Measured total fresh weight(08)

Estim

ated

tota

l fre

sh w

eigh

t by

mod

elin

g(09

)

Results Prediction of Grain dry weight using backscattering coefficients (X-band, VV)

-20 -19 -18 -17 -16 -15 -14 -13 -1210

15

20

25

30

35

40

45

f(x) = 3.14650706459764 x + 74.7163052757251R² = 0.934538297589605

Backscattering coefficients (X-band, VV, dB)

Gra

in d

ry w

eigh

t(g/m

2)

10 15 20 25 30 35 40 10

15

20

25

30

35

40

Measured grain dry weight ('08, g/m2)

Pred

icte

d gr

ain

dry

wei

ght b

y m

odel

ing(

'09,

g/m

2)

y = 1.1099x – 1.3067R2 = 0.96***

RMSE = 1.7685

Conclusions

Backscattering coefficients of rice crop were investigated with an automatically -operating ground-based scatterometer

The temporal variations of the backscattering coefficients of the rice crop at L, C, X-band during rice growth period

HH-polarization backscattering coefficients higher than VV-polarization backscattering coefficients after effective tillering stage(mid-June)

Relationships between backscattering coefficients and the rice growth parameters

Biomass, LAI was correlated with HH-backscattering coefficients in L-band

X-band was sensitive to grain maturity at near harvesting season

Prediction of rice growth parameters using backscattering coefficients in L, C, X-band