Tree Parameters retrieval and volume estimation using Terrestrial Laser Scanner: A case Study on Barkot Forest

Abstract

LiDAR is one of the fast growing remote sensing techniques. Terrestrial laser Scanner (TLS) provides precise information about forest inventory in the form of 3D point cloud. An approach to extract tree parameters: diameter at breast height (dbh) tree height and stem length followed by volume estimation has been discussed here. The area selected for the study is Barkot Forest Range in Dehradun district of Uttarakhand. The main tree species in this region are Shorea robusta (Sal), Tectona grandis (Teak), Mallotus philippensis (Indian Red Wood) and Terminalia alata (Saj). Scans were collected using Riegl vz- 400 laser scanner. Ground measurements were also recorded which included tree height and diameter at breast height (dbh). Both field measurements and TLS based computations showed excellent correlation. Forest Survey of India (FSI) in 1996 published site and species specific volumetric equations using dbh. However, three parameters: dbh, stem length and form factor have been considered in the present study. The comparative study shows excellent match between ground based measurements and TLS derived height and dbh parameters with R2 value of 0.96 and 0.98 respectively. Moreover, in respect to volume estimation, excellent correlation of 0.98 and 0.97 was achieved between the two approaches for Sal and Teak respectively. However, for Indian Red Wood, one of the estimations using FSI equation showed negative value but the present approach produced no such anomalous outcome. The reason may be attributed to the fact that FSI based volumetric equation valid only for Assam was used due to the unavailability of Barkot specific equation. Finally, volumetric equation was developed for Terminalia alata (Saj) as there is no equation available for this particular species. The study also advocates an inverse relationship between Form Factor and dbh. This new approach may prove to be indispensable for species and site specific volume estimation in near future.