Methodology comparison for effective LAI retrieving based on digital hemispherical photograph in rice canopy

Abstract

The paper investigates methodology comparisons for retrieving effective leaf area index (LAI) using digital hemispherical photograph (DHP) in rice canopy. A set of self-making DHP instrument equipped with a fish-eye Len is utilized to acquire DHP in rice canopy, and some self-developing DHP processing procedures are utilized to pre-process DHP and extract effective LAI from DHP (LAI DHP) rapidly. Based on Beer-Lambert's law and gap fraction that computed from DHP, four methods of single zenith angle (SZA), Lang, Mill formula(Mf) and iterative formula(IF) are used to derive LAI DHP(effective LAI from them are called LAI SZA, LAI Lang LAI Mf and LAI IF ,respectively). LAI SZA, LAI Lang, LAI Mf and LAI IF are inter-compared and are also compared with from AccuPAR LP-80(LAI APAR) and direct manual method (LAI direct). It is found that, in general, LAI SZA, LAI Lang LAI Mf and LAI IF are similar to LAI APAR, but slightly lower than LAIdirect. During their intercomparsion, LAI Lang is more similar to LAIAPAR than other three and LAI Mfis more similar to LAI direct, while LAI SZA and LAI Lang are almost the same. It is implied that Lang method outperformed the other three when compared with AccuPAR LP-80 and Mill formula method outperformed the other three when compared with direct manual measure. © 2011 IFIP International Federation for Information Processing.