1 National Institute for Agro-Environmental Sciences, Tsukuba, Japan2 Aomori-ITC, Kuroishi, Japan

Estimating Biophysical Variables in Rice Canopies by High-Resolution X-

and C-SAR Signatures

Yoshio Inoue 1, Eiji Sakaiya 2, Naoki Ishitsuka 1

20092008200720062005200420032002200120001999199819971996199519941993

Yield

Rice yield in Japan

1. Multi-frequencyKa --- 35.25

GHzKu --- 15.95

GHzX --- 9.60

GHzC --- 5.75

GHL --- 1.26

GHz

2. Full-PolarizationHH, HV, VH, VV

3. Multi-angularIncident angle: 20º ～ 60º

25º, 35º, 45º, 55º

Azimuth angle: -60º ～ +60º -28º, -14º, 0º, 14º, 28º

Inoue et al. (RSE 2002)

Ka 35.25

Ku 15.95

X 9.60

C 5.75

L 1.26

①

④ ③⑤

②

（GHz) ① ② ③ ④ ⑤バンド名 周波数 散乱プロセス

Ka 35.25

Ku 15.95

X 9.60

C 5.75

L 1.26

①

④ ③⑤

②

（GHz) ① ② ③ ④ ⑤バンド名 周波数 散乱プロセス

Band Freq. Scattering Name (GHz) Process

Paddy field

Objective

To investigate the capability of high-resolution satellite-SAR imagery in C- and X-bands for assessment of rice growth.

➢ Operational field scale ➢ Detailed plant data

CASI-Hyper

Tsugaru site

C-band @ 1 mHH 25º VH 21º [Radarsat-2 spotlight]Year: 2009,2010

X-band @ 1 mVV 54º VV 54º [Skymed spotlight]Year: 2009, 2010

Sky conditions for SAR

5 km

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

Frequency / Incidence angle / Polarization

Cor

rela

tion

coe

ffic

ien

t r

LAI

TotalFW

25 35 45 55 Ka

25 35 45 55 Ku

25 35 45 55 X

25 35 45 55 C

25 35 45 55 L

Inoue et al. (RSE 2002)

Ka Ku X C L

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

HH

Cro

ss VV

Frequency / Incidence angle / Polarization

Cor

rela

tion

coe

ffic

ien

t r

HeadFW

25 35 45 55 Ka

25 35 45 55 Ku

25 35 45 55 X

25 35 45 55 C

25 35 45 55 L

Inoue et al. (RSE 2002)

Ka Ku X C L

Datasets

Ground-based measurements

1. Panicle initiation stage1. Panicle initiation stage

1. Canopy height1. Canopy height

2. Hill density2. Hill density

3. Stem density3. Stem density

4. Leaf Area Index4. Leaf Area Index

5. fAPAR5. fAPAR

6. Chlorophyll index6. Chlorophyll index

7. Leaf FW, DW, W%7. Leaf FW, DW, W%

8. Stem FW, DW, W%8. Stem FW, DW, W%

9. Head FW, DW, W%9. Head FW, DW, W%

10. Total FW, DW, W%10. Total FW, DW, W%

11. Leaf number/m11. Leaf number/m22

12. Leaf length 12. Leaf length

13. Leaf width13. Leaf width

14. Leaf thickness14. Leaf thickness

15. Leaf density/m15. Leaf density/m33

16. Head layer depth16. Head layer depth

17. Leaf layer depth17. Leaf layer depth

18. Stem layer depth18. Stem layer depth

19. Stem diameter 19. Stem diameter

Major plant variablesMajor plant variables2. Maturity stage2. Maturity stage

-35

-30

-25

-20

-15

-10

-5

0

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

C-VH

σ0

(dB)

C-HH σ0 (dB)

Rice canopy

Water

13.6dB

11.4 dB 14 dB larger in rice 14 dB larger in rice

than water in HH. than water in HH.

11 dB larger in rice 11 dB larger in rice than water in VH.than water in VH.

Large differences due Large differences due to biomass, LAI, and to biomass, LAI, and geometrical geometrical structures.structures.

C-HH and C-VH C-HH and C-VH signatures signatures at panicle initiation stage (2010)at panicle initiation stage (2010)

C-V

H σ

C-V

H σ

00 (dB)

(dB)

C-HH σC-HH σ00 (dB) (dB)

VH = 0.81 HH - 11.5

Sensitivity to mass-Sensitivity to mass-related change: 24% related change: 24% higher in HH than VHhigher in HH than VH

Relations of plant variables with Relations of plant variables with C-C-HH and VH HH and VH σσ00 at panicle initiation at panicle initiation stagestage

No plant variables had close No plant variables had close correlations (r >0.5) with both correlations (r >0.5) with both HH and VH signatures. HH and VH signatures.

r = 0.5r = 0.5r= - 0.5r= - 0.5

C-VH C-VH signatures at two separate stages signatures at two separate stages in 2009 and 2010in 2009 and 2010

Variability of VH σ0 Variability of VH σ0 for rice at two for rice at two different stages was different stages was small 0.8-1.4 dBsmall 0.8-1.4 dB

For water 0.7-1.1 dBFor water 0.7-1.1 dB

Difference between Difference between rice and water was 11 rice and water was 11 dB in two years.dB in two years.-35

-30

-25

-20

-15

-10

-35 -30 -25 -20 -15 -10

C-

VH σ

0in 2010 (dB)

C-VH σ0 in 2009 (dB)

Rice canopy

Water

[2009]LAI: 3.55±0.75DW: 1386±162

[2010]LAI: 2.69±0.56DW: 419±79

11.0 dB

11.4 dB

-35

-30

-25

-20

-15

-10

-5

0 20 40 60 80

C-VH σ

0 (dB) Leaf-W%

Rice 2009

Rice 2010

Water 2009

Water 2010

r= -0.39 (n=93)

r=0.86 (n=133)

-35

-30

-25

-20

-15

-10

-5

0 0.5 1 1.5

C-VH σ

0 (dB)

h (m)

Rice 2009

Rice 2010

Water 2009

Water 2010

r=0.39 (n=93)

r=0.95 (n=133)

-35

-30

-25

-20

-15

-10

-5

0 500 1000 1500 2000

C-VH σ

0 (dB)

Total-DW (g m-2)

Rice 2009

Rice 2010

Water 2009

Water 2010

r=0.42 (n=93)

r=0.74 (n=133)

-35

-30

-25

-20

-15

-10

-5

0 0.2 0.4 0.6 0.8 1

C-VH σ

0 (dB)

fAPAR

Rice 2009

Rice 2010

Water 2009

Water 2010

r=0.19 (n=93)

r=0.96 (n=133)

-35

-30

-25

-20

-15

-10

-5

0 100 200 300

C-VH σ

0 (dB)

Leaf-DW (g m-2)

Rice 2009

Rice 2010

Water 2009

Water 2010

r=0.30 (n=93)

r=0.94 (n=133)

-35

-30

-25

-20

-15

-10

-5

0 1 2 3 4 5 6

C-VH σ

0 (dB)

LAI

Rice 2009

Rice 2010

Water 2009

Water 2010

r=0.37 (n=93)

r=0.92 (n=133)

S=0.69dB/1LAI S=13.2dB/1kg S=1.2dB/1kg

S=2.8dB/1fAPAR S=3.8dB/1m S=-0.03dB/1%

Relations of Relations of C-VH C-VH σσ00 with major plant variables with major plant variables

fAPARfAPAR

C-V

H σ

C-V

H σ

00 (dB)

(dB)

C-V

H σ

C-V

H σ

00 (dB)

(dB)

Leaf-W %Leaf-W %Plant height (m)Plant height (m)

LAILAI Leaf-DW Leaf-DW (g m-2)(g m-2) Total-DW Total-DW (g m-2)(g m-2)

-1.0 -0.5 0.0 0.5 1.0

Height (cm)

Hill density (m-2)

Stem density (m-2)

LAI (m2 m-2)

fAPAR

SPAD (DN)

Leaf-FW (gm-2)

Stem-FW (gm-2)

Total-FW (gm-2)

Leaf-DW (gm-2)

Stem-DW (gm-2)

Total-DW (gm-2)

Leaf-W (%)

Stem-W (%)

Total-W (%)

Leaves(m-2)

Leaf length (m)

Leaf width (m)

Leaf thickness (m)

Leaf density (m-3)

Layer-1 (m)

Layer-2 (m)

Layer-3 (m)

Stem Radius (m)

Correlation coefficient (r)

C-VH

Some positive relationships for Some positive relationships for mass-related variables such as mass-related variables such as LAI, fAPAR, leaf density, and LAI, fAPAR, leaf density, and biomassbiomass

No significantly high correlations (r No significantly high correlations (r >0.5) between plant variables and >0.5) between plant variables and VH signatures. VH signatures.

C-VH C-VH σ0σ0 saturated with small saturated with small amount of leaves and biomass.amount of leaves and biomass.

Relations of plant variables with Relations of plant variables with C-C-VH VH σσ00 in 2 years in 2 years

r = 0.5r = 0.5r= - 0.5r= - 0.5

-25

-20

-15

-10

-5

-25 -20 -15 -10 -5

X-VV

σ0

in 2010 (dB)

X-VV σ0 in 2009 (dB)

Water

Rice canopy

[2009]LAI: 3.55±0.75DW: 1386±162

[2010]LAI: 2.32±0.61DW: 1317±197

X-VV X-VV signatures at maturity stagesignatures at maturity stage in 2009 and 2010in 2009 and 2010

Variability of σ0 Variability of σ0 for rice 0.19 dB for rice 0.19 dB

for water 1.6 dBfor water 1.6 dB Stable and consistentStable and consistent

Average of σ0 Average of σ0 for rice -9.62 dB for rice -9.62 dB

for water -17.65 dBfor water -17.65 dB

8 dB higher in rice 8 dB higher in rice compared to watercompared to water

X-VV σX-VV σ00 in 2009 (dB) in 2009 (dB)

X-V

V σ

X-V

V σ

00 in

2010

(dB

) in

201

0 (d

B)

8.7dB

7.3dB

-20

-15

-10

-5

0 0.2 0.4 0.6 0.8 1

X-VV σ

0(dB)

fAPAR

Rice 2009

Rice 2010

Water 2009

Water 2010

r = 0.13 (n = 58)

r = 0.98 (n = 98)

-20

-15

-10

-5

0 50 100 150 200 250 300

X-VV σ

0(dB)

Leaf-DW (g m-2)

Rice 2009

Rice 2010

Water 2009

Water 2010

r = 0.05 (n = 58)

r = 0.91 (n = 98)

-20

-15

-10

-5

0 1 2 3 4 5 6

X-VV σ

0(dB)

LAI

Rice 2009

Rice 2010

Water 2009

Water 2010

r = -0.08 (n = 58)

r = 0.88 (n = 98)

S=-0.06dB/1LAIS= 1.9dB/1fAPAR

S= 1dB/1kg

X-VV

σX-

VV σ

00 (dB)

(dB)

LAILAI Leaf-DW Leaf-DW (g m-2)(g m-2) fAPARfAPAR

Relations of Relations of X-VV X-VV σσ00 with major plant variables with major plant variables

No relation with LAI, leaf-biomass, and fAPAR. No relation with LAI, leaf-biomass, and fAPAR.

Obvious difference from water surfaceObvious difference from water surface

Saturated quite early with low density of scattering Saturated quite early with low density of scattering elementselements

-55

-45

-35

-25

-15

-5

140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300

Sigma 0 (dB)

DOY

X55HH

X55Cross

X55VV

Heading HarvestingDrainage

TransplantingFlooding

Cultivation

15 d

B

15 d

B

Increase with grain growth

Seasonal change of X-VV σ0 at 55º over a rice canopy 　

Inoue et al. (RSE 2002)

Jump with transplanting

-20

-15

-10

-5

0 0.05 0.1 0.15 0.2

X-VV σ

0(dB)

Leaf length (m)

Rice 2009Rice 2010Water 2009Water 2010

r = 0.12 (n = 58)

r = 0.97 (n = 98)

-20

-15

-10

-5

0 200 400 600X

-VV σ0

(dB) Stem density (m-2)

Rice 2009Rice 2010Water 2009Water 2010

r = 0.17 (n = 58)

r = 0.96 (n = 98)

-20

-15

-10

-5

0 200 400 600 800 1000

X-VV σ

0(dB)

Stem-DW (g m-2)

Rice 2009

Rice 2010

Water 2009

Water 2010

r = 0.15 (n = 58)

r = 0.96 (n = 98)

S= 1.7dB/1kg S= 2.4dB/1k S= 0.67dB/dmX-VV

σX-

VV σ

00 (dB)

(dB)

Leaf-lengthLeaf-length(m)(m)Stem-DW Stem-DW (g m-2)(g m-2) Stem density Stem density (m-2)(m-2)

Relations of Relations of X-VV X-VV σσ00 with major plant variables with major plant variables

Little sensitivity to stem biomass, stem density, and leaf Little sensitivity to stem biomass, stem density, and leaf morphological variablesmorphological variables

Relations of Relations of X-VV X-VV σσ00 with major plant variables with major plant variables

-20

-15

-10

-5

0 200 400 600 800 1000 1200

X-VV σ

0(dB)

Head-DW (g m-2)

Rice 2009

Rice 2010

Water 2009

Water 2010

r = 0.70 (n = 58)

r = 0.98 (n = 98)

S= 5.4dB/1kg

-20

-15

-10

-5

0 500 1000 1500 2000

X-VV σ

0(dB)

Total-DW (g m-2)

Rice 2009Rice 2010Water 2009Water 2010

r = 0.47 (n = 58)

r = 0.97 (n = 98)

S= 2.1dB/1kg

X-VV

σX-

VV σ

00 (dB)

(dB)

X-VV

σX-

VV σ

00 (dB)

(dB)

Total-DW Total-DW (g m-2)(g m-2)Head-DW Head-DW (g m-2)(g m-2)

Significant sensitivity to head biomass and total biomass.Significant sensitivity to head biomass and total biomass.

Sensitivity 5 times larger than leaf and twice larger than total Sensitivity 5 times larger than leaf and twice larger than total biomass. biomass.

-13 bB may be assumed for the zero yield conditions.-13 bB may be assumed for the zero yield conditions.

-0.2 0.0 0.2 0.4 0.6 0.8

Height (cm)

Hill density (m-2)

Stem density (m-2)

LAI (m2 m-2)

fAPAR

SPAD (DN)

Leaf-FW (gm-2)

Stem-FW (gm-2)

Head-FW (gm-2)

Total-FW (gm-2)

Leaf-DW (gm-2)

Stem-DW (gm-2)

Head-DW (gm-2)

Total-DW (gm-2)

Leaf-W (%)

Stem-W (%)

Head-W (%)

Total-W (%)

Leaves(m-2)

Leaf length (m)

Leaf width (m)

Leaf thickness (m)

Leaf density (m-3)

Layer-1 (m)

Layer-2 (m)

Layer-3 (m)

Stem Radius (m)

Correlation coefficient (r)

r = 0.5r = 0.5

Summary of correlations between Summary of correlations between X-X-VV VV σσ00 and plant variables and plant variables

200

400

600

800

1000

1200

-15-14-13-12-11-10 -9 -8 -7 -6 -5

Head-

DW (g m-2

)

X-VV σ0 (dB)

2009

2010

r = 0.70 (n = 58)

• C & X backscattering signatures (σ0) of rice canopies and water were stable and consistent at 2 stages over 2 years.

Conclusions 　 (1/3)

2. The σ0 values in rice canopies were much higher than in water surfaces in both C and X bands; X:8dB; C: 11dB.

-35

-30

-25

-20

-15

-10

-35 -30 -25 -20 -15 -10

C-VH

σ0

in 2010 (dB)C-VH σ0 in 2009 (dB)

Rice canopy

Water

[2009]LAI: 3.55±0.75DW: 1386±162

[2010]LAI: 2.69±0.56DW: 419±79

11.0 dB

11.4 dB

1. The sensitivity of the present C-band SAR may not be high enough to detect plant biophysical variability.

Conclusions 　 (2/3)

• C-band σ0 were correlated weakly with canopy mass parameters such as leaf density, stem density, and biomass.

-35

-30

-25

-20

-15

-10

-5

0 1 2 3 4 5 6

C-VH σ

0(dB)

LAI

Rice 2009

Rice 2010

Water 2009

Water 2010

r=0.37 (n=93)

r=0.92 (n=133)

S=0.69dB/1LAI

C-

VH σ0

(dB)LAI

5. The X-band signature was found to be best correlated with head biomass indicating a good capability for direct assessment of rice grain yield at regional scales.

Conclusions 　 (3/3)

200

400

600

800

1000

1200

-15-14-13-12-11-10 -9 -8 -7 -6 -5Head

-DW (g m-2 )

X-VV σ0 (dB)

2009

2010

r = 0.70 (n = 58)

6. Systematic approaches would be useful to improve the accuracy; modeling/ optical sensors.