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Journal of Applied Remote Sensing

Comparison of forest aboveground biomass estimates from passive and active remote sensing sensors over Kayar Khola watershed, Chitwan district, Nepal
Author(s): Waqas A. Qazi; Shahbaz Baig; Hammad Gilani; Mirza Muhammad Waqar; Ashwin Dhakal; Ahmad Ammar
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Paper Abstract

We use passive optical high-resolution GeoEye-1 imagery and active synthetic aperture radar (SAR) Advanced Land Observing Satellite (ALOS-1) phased array type L-band synthetic aperture radar (PALSAR) L-band horizontal–horizontal-polarization imagery to estimate forest aboveground biomass (AGB) of the tropical mountainous forest test site in Kayar Khola watershed, Chitwan district, Nepal. Object-based tools were used to delineate tree crowns from the orthorectified pan-sharpened GeoEye-1 optical imagery. AGB modeling with crown projection area extracted from the optical imagery shows a good linear relationship with R 2 = 0.76 . The terrain-corrected, radiometrically calibrated, and speckle-filtered ALOS-1 PALSAR backscatter image was utilized for AGB modeling; the nonlinear modeling of AGB with the SAR backscatter (dB) shows R 2 = 0.52 . The validation R 2 values for AGB estimates from GeoEye-1 and ALOS-1 PALSAR are 0.83 and 0.44, respectively. The direct comparison of AGB estimates from both sensors is made possible by the utilization of the same set of ground survey points for both training and validation of the statistical models for both datasets. The final AGB output maps from both sensors show that the spatial patterns of AGB are in reasonable agreement at lower elevation, while SAR seems to underestimate AGB values as compared with optical-based estimates in the higher elevation zones.

Paper Details

Date Published: 24 June 2017
PDF: 16 pages
J. Appl. Rem. Sens. 11(2) 026038 doi: 10.1117/1.JRS.11.026038
Published in: Journal of Applied Remote Sensing Volume 11, Issue 2
Show Author Affiliations
Waqas A. Qazi, Institute of Space Technology (Pakistan)
Shahbaz Baig, Institute of Space Technology (Pakistan)
Hammad Gilani, Univ. of Illinois at Urbana-Champaign (United States)
International Ctr. for Integrated Mountain Development (Nepal)
Mirza Muhammad Waqar, Institute of Space Technology Islamabad (Pakistan)
Ashwin Dhakal, Kathmandu Univ. (Nepal)
Ahmad Ammar, Institute of Space Technology (Pakistan)

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