A High Precision DEM Generation Method Based on Ascending and Descending Pass TerraSAR-X/TanDEM-X BiSAR Data
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摘要: 该文基于TerraSAR-X/TanDEM-X (TSX/TDX)双基升降轨数据,首先采用非局部干涉(NonLocal Interferometric SAR, NL-InSAR)相位滤波分别得到单航过升轨和降轨模式下的高分辨率DEM。在此基础上,基于NL-InSAR估计得到的较准确相干系数,提出一种升降轨DEM融合方法,恢复SAR侧视成像造成的几何畸变,提高DEM重建精度。该文采用两幅北京地区的TSX/TDX升降轨干涉对进行融合处理,结果表明,在地形复杂地区的叠掩和阴影等无效区域,融合之后的DEM无效点数明显减少。经统计,融合后无效点数比例由升轨、降轨的4.93%和4.52%降低到1.34%。同时,融合DEM的精度相比于升轨的6.74 m提高了8.7%、相比于降轨的6.67 m提高了9.6%,融合后高程精度达到6.09 m。Abstract: A method for fine resolution and high precision Digital Elevation Model (DEM) generation using ascending and descending pass TerraSAR-X/TanDEM-X (TSX/TDX) datasets is proposed in this study. First, the NonLocal Interferometric SAR (NL-InSAR) can effectively generate ascending and descending pass raw DEMs. On this basis, the coherence well recovered by NL-InSAR is used to fusion the raw DEMs to further improve the accuracy and reduce the invalids caused by layover and shadows. This method was used to process the TSX/TDX data obtained in Beijing. The number of invalid points of DEM after fusion decreased significantly. Statistics result shows that it decreased from 4.93% in ascending raw DEM and 4.52% in descending raw DEM to 1.34% in the fusion DEM. At the same time, the accuracy of the fusion DEM increased by 9.6% compared to 6.67 m in the descending raw DEM and 8.7% compared to 6.74 m in the ascending raw DEM, reaching 6.09 m.
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表 1 升降轨DEM融合处理表
Table 1. Logic table for ascending and descending pass TanDEM-X raw DEMs fusion
升轨叠掩
/阴影降轨叠掩
/阴影升轨相干系数
小于阈值降轨相干系数
小于阈值融合DEM 1 1 – – 无效值 1 0 – 1 无效值 1 0 – 0 降轨h 0 1 1 – 无效值 0 1 0 – 升轨h 0 0 0 1 升轨h 0 0 1 0 降轨h 0 0 0 0 加权 0 0 1 1 无效值 表 2 数据集
Table 2. Datasets
数据类型 时间 轨道 垂直基线(m) 入射角(°) 模糊高度(m) TDX/TSX 2014-08-19 升轨 104.27 43.34 73.31 TDX/TSX 2014-04-07 降轨 89.22 45.86 93.21 表 3 缺失区域统计表
Table 3. Statistics table of invalids
处理方法 无效点比例(%) 升轨 4.93 降轨 4.52 融合 1.34 表 4 与SRTM DEM对比高程残差统计表(SRTM)
Table 4. Comparison of height difference with respect to SRTM DEM
处理方法 山区 平地 升轨DEM (m) 13.55 7.37 降轨DEM (m) 12.80 6.81 融合后DEM (m) 11.56 6.61 表 5 高程精度
Table 5. Accuracy of different DEMs
序号 纬度(°) 经度(°) 控制点高程值(m) 升轨DEM (m) 降轨DEM (m) 融合DEM (m) 高程值 误差 高程值 误差 高程值 误差 1 39.787079N 116.386766E 36.46 46.19 9.73 47.61 11.15 46.42 9.96 2 39.946029N 116.180640E 80.67 78.64 –2.03 75.55 –5.12 77.28 –3.39 3 39.936176N 116.163946E 83.03 76.40 –6.63 81.13 –1.90 80.00 –3.03 4 39.933121N 116.158557E 90.82 96.75 5.93 95.70 4.88 96.15 5.33 均方根误差 6.74 6.67 6.09 -
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