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Scientia Silvae Sinicae ›› 2020, Vol. 56 ›› Issue (6): 35-46.doi: 10.11707/j.1001-7488.20200604

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Forest Height Estimation Method Using TanDEM-X Interferometric Coherence Data

Yaxiong Fan1,Erxue Chen1,*,Zengyuan Li1,Lei Zhao1,Wangfei Zhang2,Yudong Jin3,Lijie Cai3   

  1. 1. Institute of Forest Resource Information Techniques, CAF Beijing 100091
    2. College of Forestry, Southwest Forestry University Kunming 650224
    3. Experimental Forest Farm of Wangyedian, Harqin Banner Chifeng 024423
  • Received:2018-04-03 Online:2020-06-25 Published:2020-07-17
  • Contact: Erxue Chen

Abstract:

Objective: Using single polarization TanDEM-X InSAR data, we studied the forest height estimation method with InSAR coherence amplitude, and analyzed the effects of different DEMs spatial resolutions (one is LiDAR DEM of 5 m resolution and the other is SRTM DEM of 30 m resolution) on forest height estimation accuracy. Method: First, non-volumetric decorrelation was corrected from the observed coherence in order to obtain the volumetric decorrelation (γVol), and then based on the SINC model, the amplitude of γVol was used to estimate forest height. Then forest height inversion results were validated against LiDAR CHM data and compared with the method based on phase difference. Plot sizes of 15 m×15 m, 30 m×30 m, 50 m×50 m and 100 m×100 m were selected to analyze the effects of spatial interpolation. Result: The effects of DEMs in two kinds of resolutions (5 m×5 m, 30 m×30 m) on inversion accuracy are small, when plot size is 100 m×100 m, the R2 are 0.54 and 0.51, the RMSEs are 2.38 m and 2.51 m, and the overall accuracies are 77.19% and 75.99%, respectively. Although the method based on phase difference has a better performance than the SINC model over different plot sizes, its results are obviously underestimated and should be calibrated with some known forest height samples. If the plot size is set as 100 m×100 m, the R2 is 0.79, the RMSEs before and after calibration are 2.57 m and 1.63 m, the overall accuracies are 75.44% and 84.41%, respectively. Conclusion: The forest height estimation method using SINC model with the TanDEM-X InSAR coherence amplitude can obtain a good performance even if using a low spatial resolution DEM, such as SRTM DEM of 30 m resolution for terrain compensation and geo-coding. Although the accuracy of SINC model is less accurate than that of phase difference method, it requires neither plot measurements for model calibration nor high-resolution DEM for terrain compensation and geo-coding, so it has the potential for large-scale forest height mapping and higher value for practical applications.

Key words: TanDEM-X, forest height, InSAR, SINC model

CLC Number: