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Using InSAR Coherence to Map Stand Age in a Boreal Forest
Department of Geographical Sciences, University of Maryland, 2181 LeFrak Hall, College Park, MD 20742, USA
Jet Propulsion Laboratory/California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109, USA
* Author to whom correspondence should be addressed.
Received: 1 October 2012; in revised form: 27 November 2012 / Accepted: 28 November 2012 / Published: 24 December 2012
Abstract: The interferometric coherence parameter γ estimates the degree of correlation between two Synthetic Aperture Radar (SAR) images and can be influenced by vegetation structure. Here, we investigate the use of repeat-pass interferometric coherence γ to map stand age, an important parameter for the study of carbon stocks and forest regeneration. In August 2009 NASA’s L-band airborne sensor UAVSAR (Uninhabited Aerial Vehicle Synthetic Aperture Radar) acquired zero-baseline data over Quebec with temporal separation ranging between 45 min and 9 days. Our analysis focuses on a 66 km2 managed boreal forest and addresses three questions: (i) Can coherence from L-band systems be used to model forest age? (ii) Are models sensitive to weather events and temporal baseline? and (iii) How is model accuracy impacted by the spatial scale of analysis? Linear regression models with 2-day baseline showed the best results and indicated an inverse relationship between γ and stand age. Model accuracy improved at 5 ha scale (R2 = 0.75, RMSE = 5.3) as compared to 1 ha (R2 = 0.67, RMSE = 5.8). Our results indicate that coherence measurements from L-band repeat-pass systems can estimate forest age accurately and with no saturation. However, empirical model relationships and their accuracy are sensitive to weather events, temporal baseline, and spatial scale of analysis.
Keywords: Synthetic Aperture Radar; Canada; coherence; disturbance; repeat pass; Quebec; regeneration; stand age; succession; temporal decorrelation; UAVSAR
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Pinto, N.; Simard, M.; Dubayah, R. Using InSAR Coherence to Map Stand Age in a Boreal Forest. Remote Sens. 2013, 5, 42-56.
Pinto N, Simard M, Dubayah R. Using InSAR Coherence to Map Stand Age in a Boreal Forest. Remote Sensing. 2013; 5(1):42-56.
Pinto, Naiara; Simard, Marc; Dubayah, Ralph. 2013. "Using InSAR Coherence to Map Stand Age in a Boreal Forest." Remote Sens. 5, no. 1: 42-56.