![]() GreenSeeker™ (Red NDVI) Performance Review Testing Summary |
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GreenSeeker™ (Red NDVI) Performance Review, Testing Summary | |||||||||||||||||||||||||||||||||||||||||||||||||||||
GreenSeeker™ (Red NDVI) Performance Review, Testing Summary (Word FILE) | |||||||||||||||||||||||||||||||||||||||||||||||||||||
Objective: · To determine performance characteristics of GreenSeeker™ Rev. G (Red NDVI) sensors Testing Parameters: · All tests were conducted under steady state conditions unless otherwise noted. At least two minutes were allowed for the sensor to reach steady state before testing commenced. 1. Step Test - dynamic response · Target description: Teal and white strip target · Height held constant at 1 m from target to photodiode window · Target moved from teal strip to white strip to teal strip, velocity = 0.08m/sec · NDVI changes as sensor moves from teal area to white area, then to teal area again · Transition zone distance = 2.7 cm
Figure 1. Dynamic Response of GreenSeeker Sensor · Conclusion: Sensor responded appropriately with little ramping effect due to target changes. 2. Time Effect on Sensor Signal · Sensor was mounted stationary over a teal and white strip target · Height was held constant at 1 m from target to photodiode window · Test was conducted for two minutes
Figure 2. Two minute elapsed time test of GreenSeeker sensor· Average NDVI = 0.816, standard deviation in NDVI = 0.0056 · Conclusion: Sensor variation in NDVI throughout the two-minute test was small. 3. Temperature Test · Tested at 7°C, 21°C, and 42°C · At least two minutes allowed for sensor to reach steady state at each temperature · Three heights (0.94 m, 1 m, and 1.3 m) tested at each temperature · Teal strip target
Table 1. Variation due to temperature of GreenSeeker sensor
· Results: Temperature has little effect on NDVI within the specified temperature range. 4. Sensor-to-target Distance Test · Tested at 21°C
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Figure 3. NDVI change with change in GreenSeeker height
· Conclusion: NDVI is independent of height over the range tested (Slope = 0.0003, R2 = 0.0542) · Standard deviation at each height is shown in Figure 4
Figure 4. Standard deviation of NDVI with respect to change in sensor height· Conclusion: Variability of data increased slightly as height increased. However, the average NDVI was approximately the same. 5. Sensitivity across field of view · Tested 5 cm white plate on teal target and 5 cm teal plate on white target · 5 cm plates moved across target strip in 2.54 cm increments · Height held constant at 0.9 m from target to photodiode window · Tested at 21°C · Tested over the designed field of view of the WeedSeeker/GreenSeeker system
Figure 6. Sensitivity to teal plate on white strip background across GreenSeeker sensor field of view· Conclusions: NDVI varied less than 8% across the field of view in the white plate on teal background test and 12% in the teal plate on white background test. 6. Sunlight effect · Height was held constant at 1.0 m from target to photodiode window · Various turf targets were used · Data was gathered in direct sunlight and with sunlight blocked with black 3 mil plastic cover
Table 2. Effect of sunlight on GreenSeeker sensor · Conclusion: Sunlight had little effect on NDVI (Mean difference = 0.00012 NDVI) 7. Plant-on-soil height test · Tested at 25°C, outdoors · Sensor positioned directly above a single plant (approx. 15 cm diameter) with a clear soil background. · Clear soil NDVI = 0.100
Figure 3. NDVI change with change in GreenSeeker height· Conclusion: Sensor can detect foliage with little variation in NDVI over a range of distances, 0.81 m to 1.22 m (32 in. to 48 in.) from canopy to photodiode window.
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