Field-Scale Sensor EvaluationField-Scale Sensor Evaluation

Ken Sudduth, Newell Kitchen, Scott Drummond Ken Sudduth, Newell Kitchen, Scott Drummond

USDA-ARSUSDA-ARS

Columbia MOColumbia MO

ObjectivesObjectives

Investigate row-to-row variability in field-scale Investigate row-to-row variability in field-scale reflectance sensor datareflectance sensor data

Document differences between data collected with Document differences between data collected with Holland Scientific Crop Circle (amber) and NTech Holland Scientific Crop Circle (amber) and NTech GreenSeeker (green)GreenSeeker (green)

N Application N Application SystemSystem

6-row system with 6-row system with sensors mounted sensors mounted over rows 2 and 5 over rows 2 and 5

System tested on System tested on 7 producer sites 7 producer sites in 2004 in 2004

Control HardwareControl Hardware

Application Control System

Green GreenSeeker

1

Green GreenSeeker

2

Crop Circle 3

Crop Circle 4

Laptop Computer

GPS

Stored Data:All sensor dataGPS dataProcessed dataValve commands

1x, 2x, and 4x Solenoid Valves

Analysis of Analysis of Response Plot Response Plot Sensor DataSensor Data

Each field site included two Each field site included two strips of N-rate response strips of N-rate response plotsplots

Reflectance data were Reflectance data were collected at the time of collected at the time of sidedress N applicationsidedress N application

Mean reflectance ratio and Mean reflectance ratio and NDVI were calculated for NDVI were calculated for each of the four sensors for each of the four sensors for each 50-foot ploteach 50-foot plot

Response Plot Reflectance Ratio DataResponse Plot Reflectance Ratio Data

N application at the Diederich (D) field was done near N application at the Diederich (D) field was done near dusk, with only diffuse lighting. Work at all other field dusk, with only diffuse lighting. Work at all other field sites was completed before 6 pm.sites was completed before 6 pm.

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Response Plot Reflectance Ratio DataResponse Plot Reflectance Ratio Data

Response Plot Sensor ComparisonDiederich Knee-High 2004

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fle

cta

nc

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ati

o,

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/NIR

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GreenSeeker Row 5

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Response Plot Reflectance Ratio DataResponse Plot Reflectance Ratio Data

Response Plot Sensor ComparisonCopeland Knee-High 2004

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26 36 46 56 66 76 86 96

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fle

cta

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ati

o,

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/NIR

GreenSeeker Row 2

GreenSeeker Row 5

Crop Circle Row 2

Crop Circle Row 5

Response Plot Sensor ComparisonSchnarre Knee-High 2004

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fle

cta

nc

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ati

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/NIR

GreenSeeker Row 2

GreenSeeker Row 5

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Crop Circle Row 5

Response Plot Reflectance Ratio DataResponse Plot Reflectance Ratio Data

Response Plot Sensor ComparisonSchnarre Knee-High 2004

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lect

ance

Rat

io, V

is/N

IR

GreenSeeker Row 2

GreenSeeker Row 5

Crop Circle Row 2

Crop Circle Row 5

Response Plot Sensor ComparisonCopeland Knee-High 2004

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26 36 46 56 66 76 86 96

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lect

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io, V

is/N

IR

GreenSeeker Row 2

GreenSeeker Row 5

Crop Circle Row 2

Crop Circle Row 5

Response Plot Sensor ComparisonDiederich Knee-High 2004

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105 115 125 135 145

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lect

ance

Rat

io, V

is/N

IR

GreenSeeker Row 2

GreenSeeker Row 5

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Crop Circle Row 5

Row-to-row differences are apparentRow-to-row differences are apparent

Is there an ambient light effect?Is there an ambient light effect?

Within a row, relative differences in Within a row, relative differences in sensor output are generally sensor output are generally consistent between sensor typesconsistent between sensor types

Scaling differences are apparent Scaling differences are apparent between sensor typesbetween sensor types

Amber reflectance vs. green reflectance?Amber reflectance vs. green reflectance? Normalize data - divide by mean of each Normalize data - divide by mean of each

sensor reading within each field sensor reading within each field

Normalized Normalized Reflectance Ratio DataReflectance Ratio Data

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NormalizedNormalized Reflectance Ratio Data Reflectance Ratio Data

Response Plot Sensor ComparisonDiederich Knee-High 2004

Mean-Normalized Data

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105 115 125 135 145

Response Plot Number

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rma

lized

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fle

cta

nc

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atio

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is/N

IR

GreenSeeker Row 2

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NormalizedNormalized Reflectance Ratio Data Reflectance Ratio Data

Response Plot Sensor ComparisonCopeland Knee-High 2004

Mean-Normalized Data

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26 36 46 56 66 76 86 96

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No

rma

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fle

cta

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io,

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/NIR

GreenSeeker Row 2

GreenSeeker Row 5

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Crop Circle Row 5

Response Plot Sensor ComparisonSchnarre Knee-High 2004

Mean-Normalized Data

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rmal

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flec

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io,

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/NIR

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GreenSeeker Row 5

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NormalizedNormalized Reflectance Ratio Data Reflectance Ratio Data

Within-site, by-sensor Within-site, by-sensor normalization removed much of normalization removed much of the sensor-type variability in the sensor-type variability in many (but not all) casesmany (but not all) cases

In practice, a similar In practice, a similar normalization is accomplished normalization is accomplished using reference strip datausing reference strip data

Well-fertilized as opposed to Well-fertilized as opposed to unfertilizedunfertilized

How well does it work?How well does it work?

Response Plot Sensor ComparisonSchnarre Knee-High 2004

Mean-Normalized Data

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Response Plot Number

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rmal

ized

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lect

ance

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io, V

is/N

IR

GreenSeeker Row 2

GreenSeeker Row 5

Crop Circle Row 2

Crop Circle Row 5

Response Plot Sensor ComparisonCopeland Knee-High 2004

Mean-Normalized Data

0.4

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26 36 46 56 66 76 86 96

Response Plot Number

No

rmal

ized

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lect

ance

Rat

io, V

is/N

IR

GreenSeeker Row 2

GreenSeeker Row 5

Crop Circle Row 2

Crop Circle Row 5

Response Plot Sensor ComparisonDiederich Knee-High 2004

Mean-Normalized Data

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Response Plot Number

No

rmal

ized

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lect

ance

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io, V

is/N

IR

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GreenSeeker Row 5

Crop Circle Row 2

Crop Circle Row 5

N Rec = -200 +250

VisibleNIR

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Target

Reference

(( )

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Target

Reference

(( )

)

Comparing Sources of VariationComparing Sources of Variation

Sensor Variation

Row-to-row Variation

0.4 0.8 1.2 1.6 2Gre e n Se e ke r N o rm a lize d R a tio , R o w 2

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Comparing Sources of VariationComparing Sources of Variation

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Considerable variability in ratio (or Considerable variability in ratio (or NDVI) readings between sensor typesNDVI) readings between sensor types

Mean normalization removed much of Mean normalization removed much of the variationthe variation

The remaining variation was of similar The remaining variation was of similar magnitude as the variation between magnitude as the variation between corn rows 90 inches apartcorn rows 90 inches apart

How many sensors are needed to How many sensors are needed to “adequately” describe variability?“adequately” describe variability?

More in MO where we can’t seem to get More in MO where we can’t seem to get uniform corn stands?uniform corn stands?

Does Between-Sensor Variability Affect N Rate? Does Between-Sensor Variability Affect N Rate?

476800 476900 477000 477100 477200 477300 4774004349100

4349150

4349200

4349250

476800 476900 477000 477100 477200 477300 4774004349100

4349150

4349200

4349250

R ela tive R eflectance R atio , G reenSeeker Sensor 2

R ela tive R eflectance R atio , C rop C irc le Sensor 3

Does Between-Sensor Variability Affect N Rate? Does Between-Sensor Variability Affect N Rate?

4349150

4349200

4349250

4349150

4349200

4349250

N tech Sensor 2

C rop C ircle Sensor 3

N R ates

1 2 3 4 5 6 7

In this case, there was not much effect when looking at In this case, there was not much effect when looking at large-scale patterns of N rate changeslarge-scale patterns of N rate changes

Does Between-Sensor Variability Affect N Rate? Does Between-Sensor Variability Affect N Rate?

2 4 6

Crop C ircle Rate

2

4

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ate

0 - 3 3 - 6 6 - 9 9 - 12 12 - 15 15 - 18 18 - 21 21 - 24

N Rec = -150 +180

VisibleNIR

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Target

Reference

(( )

)N Rec = -150 +180

VisibleNIR

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2 4 6

2

4

6

Strong relationship between rates from the two sensors, but Strong relationship between rates from the two sensors, but somewhat offset from 1:1 linesomewhat offset from 1:1 line

Does Between-Sensor Variability Affect N Rate? Does Between-Sensor Variability Affect N Rate?

In some fields, GreenSeeker N In some fields, GreenSeeker N rate range was considerably rate range was considerably reduced compared to Crop Circlereduced compared to Crop Circle

Diederich field was a worst-case Diederich field was a worst-case example, perhaps because of a example, perhaps because of a different relationship between the different relationship between the two sensor outputs in low lighttwo sensor outputs in low light

2 4 6

G reenSeeker N R ate

2

4

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0

50

100

150

200

250

300

350

400

450

500

550

D iederich, Sensors 2,3

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SummarySummary

Sensor “types” are differentSensor “types” are different

So are individual crop rows, at a similar magnitudeSo are individual crop rows, at a similar magnitude

Application rates with the different sensors are similar Application rates with the different sensors are similar in some field conditions, but not in othersin some field conditions, but not in others

Are sensors interchangeable within algorithms, or do Are sensors interchangeable within algorithms, or do we need to consider them as a “package”?we need to consider them as a “package”?