Height Measurement and Forage Biomass Estimation Using Laser and Ultra Sonic Sensors From a Mobile Platform.

Height is correlated with biomass when examined for various plant species. The estimation of biomass using Laser and Ultrasonic sensor height measurements was compared to quad harvest measurements as well as plate meter and physical height (meter stick) measurements. The instruments were operated as mounted to a mobile platform (electric golf cart) such that height measurements could be collected while moving across the trial areas. Four different sensor configurations were examined to assess which was the most accurate means of biomass estimation. All sensors were oriented at 1.2 meters above ground surface and calibrated at ground surface for minimum and 1 meter for maximum. One of each ultrasonic sensors operating at 240KHz and 120KHz were implemented such to examine the influence of signal frequency on accuracy in biomass estimation. Additionally two identical laser distance measuring instruments which used time-of-flight methodology were also examined for effectiveness in biomass estimation. Single laser sensor measurements as well an average for both sensors were examined for accuracy in biomass estimation. Tall fescue (Festuca arundinacea Schreb.), Alalfa (Medicago sativa L.), and Chicory (Cichorium intybus L.) were chosen as the forage types for measurement due to differences in physical characteristics which provided comparisons of accuracy of methods between species. Laser height measurements were observed to have r²-values of 0.78 as compared to 0.01 r²-values from the ultrasonic readings when regressed with dry matter yield. This suggests the laser is a more accurate means of height measurement and subsequently forage mass estimation.