Suitability of a laser rangefinder to characterize winter wheat

Abstract

In recent years, laser rangefinder sensors have been introduced to the practice and research of agricultural engineering. In research, laser rangefinders have been investigated in horticulture and agriculture. For vehicle-based determination of crop biomass, commercially available laser rangefinders have been analysed and tested to measure aboveground biomass in oilseed rape, winter rye, winter wheat, oats and grassland. Resulting from limited measuring range and fixed beam types, the laser rangefinder models that were investigated only partially met the specific demands for agricultural field and crop conditions. Therefore, a new laser rangefinder scanner (ibeo-ALASCA XT) was chosen. This sensor was specifically developed for driver assistance and autonomous guiding of road vehicles. The scanner was tested in 2008 focusing on the measurement of crop stand parameters in winter wheat under field conditions. The sensor achieved good results with reproducible measurements. Measuring from a stationary vehicle, the standard deviation for the measurements of crop height to characterise the crop stand was less than 3 mm in low, medium, and high biomass areas. The ground speed of the vehicle, ranging from 6 to 24 km h -1 , did not significantly influence the readings. For measurements in front of tractors and self-propelled machines (field sprayers, combines and forage harvesters), the sensor has to scan the crop stands at different inclination angles. It was shown that the inclination angle of the laser beam, which varied from 10°to 80°, significantly influenced the readings. Higher inclination angles resulted in apparent increased heights of the crop stand. For the functional relationship between reflection height levels (95th, 75th, 50th and 25th percentiles, and mean values) and crop biomass density, the coefficient of determination (R 2 ) was greater than 0.9.

Monitoring Agronomic Parameters of Winter Wheat Crops with Low-Cost UAV Imagery

“…They related either the vegetation volume or the reflection height (distance between crop surface and laser scanning unit) derived by triangulation or time-of-flight of the reflected laser beam with biomass and LAI measurements. The studies reported R 2 values for FBM between 0.77 and 0.99, for DBM between 0.72 and 0.99 and for LAI between 0.70 and 0.96 [22,54,55]. Sensing LAI was further investigated using a combined radiometer and ultra-sound sensing system yielding an R 2 value of 0.84 [24] and a mobile LAI system based on canopy light transmittance yielding R 2 values ranging from 0.73 to 0.86 [20] between the sensor and LAI reference measurements.…”

Method for estimating rice plant height without ground surface detection using laser scanner measurement

“…11,12 In a previous study of plant height determination, Ehlert et al [13][14][15] proposed an approach of observing plant height in flat areas with a known ground level. The laser scanner is mounted on a tool carrier with an inclination angle (φ) to observe the plant from above.…”

Precision phenotyping of biomass accumulation in triticale reveals temporal genetic patterns of regulation

“…The accumulation of biomass is central to agricultural productivity but the non-invasive monitoring of biomass using various sensors has thus far yielded only moderate prediction accuracies789. This may be attributed to the failure in combining information derived from different but complementary types of sensors10.…”