Effects of distance to Effects of distance to target, time of the day, target, time of the day,

wetness of the leaves, and wetness of the leaves, and sensor position on active sensor position on active

sensor readingssensor readings

Fernando Solari, Paul Hodgen, Fernando Solari, Paul Hodgen, John Shanahan, and Jim John Shanahan, and Jim

SchepersSchepers

ObjectivesObjectives

To determine howTo determine how Sensors distance to the target Sensors distance to the target Time of the day Time of the day Wetness of the leaves Wetness of the leaves Shifts from on row positionShifts from on row position

Affects sensor readings outputs Affects sensor readings outputs

sensor

GDO

BARE SOIL

CORN V4

CORN V10

Distance to targetDistance to targetCrop Circle -IR upwelling radiance

0

1

2

3

4

5

6

7

8

9

40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210

Distance to the target (cm)

IR u

p-r

ad

grass NIR

Bare soil IR

Corn V4 IR

Corn V10 IR

Distance to targetDistance to targetCrop Circle-Amber upwelling radiance

0

0.2

0.4

0.6

0.8

1

1.2

40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210

Distance to the target (cm)

Am

be

r u

p-r

ad grass Amber

Bare soil Amber

Corn V4 Amber

Corn V10 V4

Distance to targetDistance to targetCrop circle-ANDVI

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210

Distance to the target (cm)

AN

DV

I

grass ANDVI

Bare soil ANDVI

Corn V4 ANDVI

Corn V10 ANDVI

cv2% 2% 4%

Crop circle-ANDVI-cvCrop circle-ANDVI-cvDistancDistancee

GrassGrass Bare Bare SoilSoil

Corn V4Corn V4 Corn Corn V10V10

40-100 40-100 cmcm

1%1% 1%1% 3%3% 2%2%

101-101-140140

cmcm

1%1% 5%5% 4%4% 2%2%

40-14040-140

cmcm1%1% 4%4% 8%8% 4%4%

VI=(VI=(ρρ-1 -1 VIS- VIS- ρρ-1 -1 IRIR) * ) * ρρ IRIR (IR/Amber)-1

0

1

2

3

4

5

6

7

40 60 80 100 120 140

Distance to the target (cm)

VI

grass

bare soil

corn v4

cornv10

1%

1%

6%

3%

Distance to targetDistance to targetGNDVI Green Seeker

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210

Distance to the target (cm)

GN

DV

I

Grass

Corn V10

Corn V4

Bare soil

36in+-14in

CV 7%

35+-7

CV 4%

GreenSeeker-GNDVI-cvGreenSeeker-GNDVI-cv

GrassGrass Bare Bare soilsoil

Corn V4Corn V4 Corn Corn V10V10

55-125 55-125 cmcm

4%4% 14%14% 5%5% 7%7%

70-105 70-105 cmcm

9%9% 9%9% 5%5% 4%4%

Distance to targetDistance to targetConclusionsConclusions

Crop Circle: 40 to 100 cm lowest CV Crop Circle: 40 to 100 cm lowest CV for NDVI and Gitelson VIfor NDVI and Gitelson VI

GreenSeeker: 70-105 cm lower CV GreenSeeker: 70-105 cm lower CV than 55-125cmthan 55-125cm

Time of the day effect study

8:00

12:00 17:00

Time of the day effect study

Crop circle - 8:00Crop circle - 8:00Corn V12. Crop circle. 8am

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 10 20 30 40 50 60 70 80

distance (cm)

AN

DV

I

rep 1

rep2

rep3

rep4

rep5

rep6

GreenSeeker – 8:00GreenSeeker – 8:00Corn V12 Green Seeker

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 10 20 30 40 50 60 70 80 90

distance (cm)

GN

DV

I

rep1

rep 2

rep3

rep4

rep5

rep6

Crop circle – 12:00Crop circle – 12:00Corn V12. Crop Circle 12hs

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 10 20 30 40 50 60 70

distance (cm)

AN

DV

I

rep1

rep2

rep3

rep4

rep6

GreenSeeker – 12:00GreenSeeker – 12:00Corn V12. Green Seeker

12hs

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 10 20 30 40 50 60 70 80

distance (cm)

GN

DV

I

rep 1

rep 2

rep 3

rep 4

rep 5

rep 6

Crop circle – 17:00Crop circle – 17:00Corn V12. Crop circle 17hs

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 20 40 60 80 100 120

distance (cm)

AN

DV

I

rep1

rep2

rep3

rep4

rep5

rep6

GreenSeeker – 17:00GreenSeeker – 17:00Corn V12. Green Seeker. 17hs

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 20 40 60 80 100 120 140 160

Distance (cm)

GN

DV

I

rep1

rep2

rep3

rep4

rep5

rep6

Crop CircleCrop CircleCorn V12. Crop circle

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 10 20 30 40 50 60 70 80

distance (cm)

AN

DV

I average ANDVI 8

average ANDVI 12

average ANDVI 17

GreenSeekerGreenSeekerCorn V12. Green Seeker

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 20 40 60 80 100

Distance (cm)

GN

DV

I average GNDVI 8 am

average GNDVI 12 am

average GNDVI 17

Table 1: NDVI valuesTable 1: NDVI values

Time of Time of the daythe day

CCCC

V10V10CCCC

V12V12GSGS

V10V10GSGS

V12V12

8:008:00 0.62c0.62c 0.73a0.73a 0.67b0.67b

12:0012:00 0.55a0.55a 0.69a0.69a 0.44b0.44b 0.64a0.64a

17:0017:00 0.58b0.58b 0.67a0.67a 0.42a0.42a 0.68c0.68c

Different letters are significant differences within column (sensor and stage)

Time of the day effect studyTime of the day effect studyConclusionsConclusions

Time of the day can affect sensor Time of the day can affect sensor readings readings

(Growth?, Wind?, Power supply,?)(Growth?, Wind?, Power supply,?)

How important is to be on the row?

Across rowsAcross rowsGNDVI Head parallel to the row

Corn V7, 76cm wide

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200

Distance across the rows (cm)

GN

DV

I

Across rowsAcross rowsGreenSeeker(red). Head parallel to the row

Corn V12

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160

distance across row (cm)

NDVI

Across rowsAcross rowsCrop Circle. Across the row.

Corn V7, 76cm wide

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200

Distance across the rows (cm)

AN

DV

I

Across rowsAcross rowsCrop circle. Head parallel to the row. Corn V12

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

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

Distance across the row (cm)

ANDV

I

91 cm

ROWROW

6 in=15cm

Corn V10-KansasCorn V10-KansasANDVIANDVI

Crop circle (Kansas data Corn V10)

y = 1.3552x - 0.1925

R2 = 0.5575

0.4

0.45

0.5

0.55

0.6

0.65

0.7

0.75

0.8

0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8

ANDVI (NADIR position 4 inch left)

AN

DV

I (N

AD

IR p

osi

tio

n)

Corn V10 KansasCorn V10 KansasWDRVIWDRVI

Crop Circle (Kansas data Corn V10)

y = 1.0178x + 0.0404

R2 = 0.6914

-0.05

0

0.05

0.1

0.15

0.2

0.25

-0.05 0 0.05 0.1 0.15 0.2 0.25

WDRVI (NADIR position 4 inch left)

WD

RV

I (N

AD

IR p

osi

tio

n)

Corn V9-ArgentinaCorn V9-ArgentinaGreenSeekerGreenSeeker

GreenSeeker (Argentina data Corn V9)

y = 1.3706x + 0.009

R2 = 0.7842

0

0.05

0.1

0.15

0.2

0.25

0 0.05 0.1 0.15 0.2 0.25

GNDVI (NADIR position 6 inch left)

GN

DV

I (N

AD

IR p

osi

tio

n )

On the row studyOn the row studyConclusionConclusion

The principal effect of to be off the The principal effect of to be off the row is underestimation. row is underestimation.

The effect is much more important at The effect is much more important at early stages. early stages.

wetness of the leavesrep1

0.6

0.65

0.7

0.75

0.8

0 20 40 60 80 100 120

distance (cm)

AN

DV

I andvi before

andvi watering

andvi after

How important is dew presence or sprinkle?

Wetness of the leavesWetness of the leavesWetness of the leaves-(Crop Circle)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

before watering after

Treatment

AN

DV

I

aa a

ConclusionsConclusions

Distance:Distance: GreenSeeeker: 80-110cm cm to targetGreenSeeeker: 80-110cm cm to target Crop Circle: 40-100 cm to targetCrop Circle: 40-100 cm to target

Time of the dayTime of the day Time of the day can affect sensor readings Time of the day can affect sensor readings

(Growth?, Wind?, Power supply,?)(Growth?, Wind?, Power supply,?) PositionPosition

Important to be on row (If not, underestimation)Important to be on row (If not, underestimation) WateringWatering

Does not affect Does not affect