Dhp-based forest lai measurements for meter-scale remote sensing validation

Leaf area index (LAI) is a critical indicator for modeling global biosphere-climate interactions. Accurately measuring forest LAI significantly affects the objectivity and accuracy of LAI remote sensing products. DHP is the most widely used instrument to measure forest LAI. However, it is challenging to measure forest LAI accurately using DHP at meter-scale as the wide viewing angle range of DHP is not appropriate for validation of high-resolution pixels. To address this issue, a geometric-based method was proposed to obtain the optimal view zenith range for DHP-based LAI field measurements at meter-scale in this study. Three virtual forest scenes were generated by LESS (LargE-Scale remote sensing data and image Simulation framework) and field measurements at Saihanba, in northern China was collected. The validation results indicate a good agreement between LAI estimation using proposed method and reference LAI datasets. The R2 between the LESS-derived LAI and DHP-derived LAI are all greater than 0.9, and the RMSE are all less than 0.1 in simulated scenes. Meanwhile, the R2 between the UAV lidar-derived LAI and DHP-derived LAI is 0.668 with RMSE of 0.376. In conclusion, this study holds potential in measuring forest LAI at meter-scale.