Assessment of in situ crop LAI measurement using unidirectional view digital photography

► Assessed two unidirectional photographic methods for in situ crop LAI measurements. ► Accounted for clumping effects and evaluated errors in LAI estimation. ► Canopy GAI is measured better with effective GAI at nadir and total GAI at 57.5°. ► The nadir extinction coefficient needs to be corrected from 0.5 to 0.61. ► Canopy structural variation (especially wheat) induces uncertainty in GAI estimation.