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Open AccessArticle

The Comparison of Canopy Height Profiles Extracted from Ku-band Profile Radar Waveforms and LiDAR Data

1
Electronic Information School, Wuhan University, Wuhan 430079, China
2
Department of Remote Sensing and Photogrammetry, Finnish Geospatial Research Institute, Kirkkonummi FI-02431, Finland
3
School of automation, Nanjing University of Science and Technology, Nanjing 210094, China
4
Shanghai Key Laboratory of Navigation and Location-based Services, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200241, China
*
Author to whom correspondence should be addressed.
Remote Sens. 2018, 10(5), 701; https://doi.org/10.3390/rs10050701
Received: 5 March 2018 / Revised: 14 April 2018 / Accepted: 25 April 2018 / Published: 3 May 2018
(This article belongs to the Section Forest Remote Sensing)
An airborne Ku-band frequency-modulated continuous waveform (FM-CW) profiling radar, Tomoradar, records the backscatter signal from the canopy surface and the underlying ground in the southern boreal forest zone of Finland. The recorded waveforms are transformed into canopy height profiles (CHP) with a similar methodology utilized in large-footprint light detection and ranging (LiDAR). The point cloud data simultaneously collected by a Velodyne® VLP-16 LiDAR on-board the same platform represent the frequency of discrete returns, which are also applied to the extraction of the CHP by calculating the gap probability and incremental distribution. To thoroughly explore the relationships of the CHP derived from Tomoradar waveforms and LiDAR data we utilized the effective waveforms of one-stripe field measurements and comparison them with four indicators, including the correlation coefficient, the root-mean-square error (RMSE) of the difference, and the coefficient of determination and the RMSE of residuals of linear regression. By setting the Tomoradar footprint as 20 degrees to contain over 95% of the transmitting energy of the main lobe, the results show that 88.17% of the CHPs derived from Tomoradar waveforms correlated well with those from the LiDAR data; 98% of the RMSEs of the difference ranged between 0.002 and 0.01; 79.89% of the coefficients of determination were larger than 0.5; and 98.89% of the RMSEs of the residuals ranged from 0.001 to 0.01. Based on the investigations, we discovered that the locations of the greatest CHP derived from the Tomoradar were obviously deeper than those from the LiDAR, which indicated that the Tomoradar microwave signal had a stronger penetration capability than the LiDAR signal. Meanwhile, there are smaller differences (the average RMSEs of differences is only 0.0042 when the total canopy closure is less than 0.5) and better linear regression results in an area with a relatively open canopy than with a denser canopy. View Full-Text
Keywords: Ku band profile radar; LiDAR; power waveform; point cloud; canopy height profile Ku band profile radar; LiDAR; power waveform; point cloud; canopy height profile
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Zhou, H.; Chen, Y.; Feng, Z.; Li, F.; Hyyppä, J.; Hakala, T.; Karjalainen, M.; Jiang, C.; Pei, L. The Comparison of Canopy Height Profiles Extracted from Ku-band Profile Radar Waveforms and LiDAR Data. Remote Sens. 2018, 10, 701.

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