Laboratory evaluation of the GreenSeekerTM handheld optical sensor to variations in orientation and height above canopy

Handheld optical sensors recently have been introduced to the agricultural market. These handheld sensors are able to provide operators with Normalized Difference Vegetative Index (NDVI) data when cloud cover prevents acquisition of satellite or aerial images. This research addressed the sensitivity of the GreenSeeker handheld optical sensor to changes in orientation and height above a ryegrass canopy. Planter boxes were oriented both parallel and perpendicular to the light beam from the sensor head and heights of 30.5 cm (12”), 61.0 cm (24”), 91.5 cm (36”), 122 cm (48”) and 152 cm (60”) were tested. Results indicated that the sensor was highly sensitive (P<0.0001) to both height above canopy and orientation of the sensor relative to the target. Operators should follow manufacturer’s recommendations on operating height range of 81 – 122 cm and orient the sensor head in-line with the target to obtain maximum signal response.