1. Progress in Sensor Development Marvin Stone OSU Sensor Workshop, January 2008

2. Evolution of OSU Optical Sensor Based Variable Rate Applicator
1996
1992
1997
1998
2001

3. OSU Variable Rate Technology - 1996

4. Sensor Design

5. Sensor Based Precision Farming - 1996
Variable Rate
Spray Nozzle
Decision Making
And Agronomic Strategy
Computer and
Sensor
Assembly
Direction
of Travel
Plant

6. GreenSeeker™ Sensor Based Fertilizer Applicator - 2001
The Oklahoma State University and Ntech Industries, Inc.

7. Greenseeker™ Applicator
Sense and treat each 2 ft by 2 ft area
Apply one of seven fertilizer rates based on the crops yield potential
Accomplish this while driving 15 mph
Operate day or night
Provide the capability to detect and treat other plant problems
Record and georeference sensor data for GIS analysis
Sense and spot spray weeds (current Patchen technology)

8. Early Handheld GreenSeeker™ - 2001

9. Algorithm development 1998-2006
NDVI at F5
INSEY =
Days from planting to sensing, GDD>0
Winter Wheat
Units: biomass, kg/ha/day, where GDD>0

10. Algorithm development
2001 10

11. Absorption of Visible Light by Photo-pigments
Sunlight
Intensity
Chlorophyll b
Phycocyanin
B-Carotene
Chlorophyll a
Absorption
Wavelength, nm
Lehninger, Nelson and Cox

12. Spectral Response to Nitrogen Winter wheat
Measure of living plant cell’s ability to reflect infrared light
Photosynthetic Potential

13. Interfering Inputs: Soil Reflectances - Oklahoma

14. NDVI Normalized Difference Vegetative Index
Developed as an irradiance based index for remote sensing
Varies from -1 to 1
Soil NDVI = to .05
Plant NDVI = 0.6 to 0.9
Typical plants with soil background NDVI=
NDVI from different sensors vary
Bandwidths for Red, NIR vary
Irradiance vs. reflectance based

15. Greenseeker™ Sensing Technique

16. Greenseeker Optics

17. 4-Band Sensor Multi-band sensing Higher reflectance sensitivity
Can measure NDVI as well as other indices
N-Uptake
Water content
Other color related parameters
Higher reflectance sensitivity
Less height sensitivity
Four selectable illuminators
Single detector

18. 4-Band Geometry

19. 4-Band Calibration and repeatability

20. Competitive sensors Spectrum™ CM 1000 Chlorophyll Meter
Measures reflected light in near infrared and returns an index
Minolta SPAD 502 Meter
Clamp the meter over leafy tissue, and receive an indexed chlorophyll content reading (0-99.9) in less than 2 seconds.
TCM 500 NDVI Turf Color Meter
Measures reflected light from turf grass in the red (660 nm) and near infrared (780 nm -NIR) spectral bands. NDVI denotes Normalized Difference Vegetative Index.
Crop Circle ACS-210 Plant Canopy Sensor
Measure reflected light in the red and near infrared bands and computes NDVI.

21. OPS technology
Low cost
Low power
Moderate features
No wires

22. Discussion