一种新的X波段单航过干涉SAR森林地上生物量估测方法

A New Approach for Forest Aboveground Biomass Estimation Using X-band Single-Pass Interferometric SAR Data

  • 摘要: 森林地上生物量(Aboveground Biomass,AGB)是衡量森林生态系统生产力的关键指标,其精确测量对于森林资源的监测与管理具有重要意义。本研究基于高分辨率X波段单航过干涉合成孔径雷达(Interferometric Synthetic Aperture Radar,InSAR)数据和少视干涉等技术发展了一种新的森林地上生物量估测方法。首先,基于少视干涉处理InSAR数据得到初始的数字地表模型(Digital Surface Model,DSM);其次,采用低通滤波技术去除初始干涉DSM中的地形趋势,在此基础上构建森林的垂直结构剖面;然后,基于剖面提取能够反映森林的垂直和水平结构信息的多个特征;最后,构建森林AGB估测模型,实现森林AGB的精准估测。在内蒙古呼伦贝尔市伊根农林交错区附近的森林区域,基于机载X波段单航过InSAR数据对提出的方法进行了验证。该方法的估测精度为80.98%,R2为0.89,RMSE为3.15t/hm2,与传统基于干涉差分法提取森林高度估测森林AGB的方法相比,估测精度提高了6.8%。研究结果同时表明本文提出的方法构建的森林垂直结构剖面,可以有效地提取反映森林高度信息的剖面高度特征和反映森林密度信息的剖面面积衍生特征,而通过这些特征联合的联合可实现对森林AGB的精准估测。

     

    Abstract: Objectives: Forest aboveground biomass (AGB) is a crucial indicator for assessing forest ecosystem productivity, and its accurate estimation is vital for effective monitoring and sustainable management of forest resources. Traditional methods for estimating forest AGB using InSAR typically rely on a single forest height feature for AGB estimation, which suffers from poor robustness and limited accuracy. Addressing the aforementioned issues, this study aims to utilize few-look interferometric and local histogram statistics techniques to extract more forest structural parameters, thereby enhancing the estimation accuracy of forest AGB. Methods: This study proposes a novel approach for forest AGB estimation using high-resolution X-band single-pass InSAR data, which integrates the few-look interferometric technique, low-pass filtering, and local histogram statistics. The implementation procedure involves four key steps. Firstly, an initial Digital Surface Model (DSM) is generated via few-look interferometric processing of InSAR data. Secondly, low-pass filtering technology is employed to remove the terrain trend from the initial InSAR DSM, upon which the vertical structure profile of the forest is constructed. Then, multiple features reflecting the vertical and horizontal structural information of the forest are extracted based on the profile. Finally, a forest AGB estimation model is constructed to achieve accurate estimation of forest AGB. Results: The proposed method was experimentally validated using high-resolution airborne X-band single-pass InSAR data. We found that the forest vertical profile constructed from the differential phase heights can effectively characterize the distribution patterns of forest structure. The features extracted from the vertical structure profile exhibit strong correlations with forest biomass (correlation coefficient R > 0.80, P< 0.05). Among these features, DH5 showed the highest correlation with forest AGB, with a correlation coefficient of 0.94. And the estimation accuracy of the proposed method was 6.8% higher than that of traditional InSAR methods based on interferometric phase difference for forest height estimation. Specifically, the model achieved an overall accuracy of 80.98%, with a coefficient of determination (R2) of 0.89 and a root mean square error (RMSE) of 3.15 t/hmR2. Conclusions: Based on the few-look interferometric and local height histogram statistical techniques, it is possible to effectively construct the vertical structural profile of forests and extract feature parameters sensitive to forest AGB. Compared with the single height feature estimation method, the multi feature joint estimation method significantly improves the accuracy of forest AGB estimation. Compared with traditional methods based on interference difference to extract forest height and forest AGB, the accuracy has been improved by about 6.8%. The method proposed here provides a new approach and method for accurate estimation of forest AGB in high-resolution interferometric SAR. However, the applicability of this method in different data sources and study areas still needs further research in the future.

     

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