PocketLAI measures LAI based on photographs taken by smartphones from specific angle. Multiple images have to be taken to get representative LAI.
PocketLAI measures a gap fraction at fixed view angle (57. 5o). It uses accelerometer device in the smartphones to acquire images at 57.5o and uses mobile camera to capture luminance. Gap fraction is derived by processing images through segmentation algorithm that identifies dark leaf pixels in the images.
The PocketLAI measurements have been tested against destructively measured LAI in the rice field (example of homogeneous canopy) as well as indirectly measured LAI using other sophisticated instruments in the maize field, giant reed and grassland canopies. In general, the accuracy and reproducibility were better in the homogeneous canopies compared to heterogeneous once.
Confalonieri, R., Francone, C. & Foi, Marco. The PocketLAI smartphone app: an alternative method for leaf area index estimation. in International Congress on Environmental Modelling and Software 41, 288–293 (2014).