LAI can be measured directly by destructive methods wherein all leaves from a sampling plot of known area are plucked and their collective one-sided leaf area is measured. Ratio of this collective one-sided leaf area with the plot ground area gives estimate of LAI. However, this is very time consuming and laborious method.
Many scientifically tested methods are available to estimate LAI indirectly. Although there are differences in terms of working principles and accuracies among the indirect methods, all of these methods use some sort of radiation based information to calculate LAI. Researchers generally use scientific instruments developed specifically for LAI measurements, however, recently some mobile apps and image analysis softwares have also been developed for quick surveys. It is important to calibrate and test these apps for scientific research quality data.
Details of some instruments developed for indirect LAI measurements:
Details of some mobile apps/softwares for indirect LAI measurements: