1. Effects of distance to target, time of the day, wetness of the leaves, and sensor position on active sensor readings Fernando Solari, Paul Hodgen, John Shanahan, and Jim Schepers

2. Objectives To determine how • Sensors distance to the target • Time of the day • Wetness of the leaves • Shifts from on row position Affects sensor readings outputs

3. GDO sensor

4. BARE SOIL

5. CORN V4

6. CORN V10

7. Distance to target

8. Distance to target

9. Distance to target 2% cv2% 4%

10. Crop circle-ANDVI-cv

11. VI=(ρ-1 VIS- ρ-1 IR) * ρIR 1% 3% 6% 1%

12. Distance to target 36in+-14in CV 7% 35+-7 CV 4%

13. GreenSeeker-GNDVI-cv

14. Distance to targetConclusions • Crop Circle: 40 to 100 cm lowest CV for NDVI and Gitelson VI • GreenSeeker: 70-105 cm lower CV than 55-125cm

15. Timeof the day effect study

17. Timeof the day effect study 8:00 17:00 12:00

18. Crop circle - 8:00

19. GreenSeeker – 8:00

20. Crop circle – 12:00

21. GreenSeeker – 12:00

22. Crop circle – 17:00

23. GreenSeeker – 17:00

24. Crop Circle

25. GreenSeeker

26. Table 1: NDVI values Different letters are significant differences within column (sensor and stage)

27. Time of the day effect studyConclusions • Time of the day can affect sensor readings • (Growth?, Wind?, Power supply,?)

28. How important is to be on the row?

31. Across rows

32. Across rows

33. Across rows

34. Across rows 6 in=15cm 91 cm ROW ROW

35. Corn V10-KansasANDVI

36. Corn V10 KansasWDRVI

37. Corn V9-ArgentinaGreenSeeker

38. On the row studyConclusion • The principal effect of to be off the row is underestimation. • The effect is much more important at early stages.

39. How important is dew presence or sprinkle?

40. Wetness of the leaves a a a

41. Conclusions • Distance: • GreenSeeeker: 80-110cm cm to target • Crop Circle: 40-100 cm to target • Time of the day • Time of the day can affect sensor readings (Growth?, Wind?, Power supply,?) • Position • Important to be on row (If not, underestimation) • Watering • Does not affect