中国大陆地区TanDEM-X 90 m DEM误差空间分布特征

TanDEM-X 90 m 数字高程模型（DEM）在其原始雷达影像的采集与DEM产品生产过程中,坡度、坡向和地表覆盖物等 因素都会对误差产生一定的影响。为了便于该数据更好地为各领域的研究提供服务,本文以整个中国大陆为研究区域,运用ICESat/GLA14数据对该区域的TanDEM-X 90 m DEM对应位置的高程数据进行提取统计,对比分析了我国陆地区域 TanDEM-X DEM数据与GLA14高程点数据的整体误差精度,并提取坡度、坡向地形因子,研究TanDEM-X 90 m DEM误差在不同坡度、不同坡向以及不同地表覆盖物影响下的分布规律。结果表明：① TanDEM-X 90 m DEM在中国区域整体的绝对误差均值为3.89 m,中误差为9.03 m,标准差为8.85 m; ② 受地形因子的影响,在坡度<3°时,绝对误差均值仅为1.29 m,标准差为2.84 m; 在坡度>25°时,绝对误差均值20 m以上,标准差也达到30 m左右,即误差随着坡度的上升逐渐增大;③ 坡向对误差也有一定影响,在南北方向的绝对误差均值明显比东西方向小;④ 受地表覆盖物影响较大,在荒地误差最小,绝对误差均值仅为 1.85 m,但在冰川积雪区绝对误差均值达到12.68 m。通过与无人机获取的等高线及剖面图对比分析发现,TanDEM-X 90 m DEM能较好地反映真实地形情况。最后,根据不同影响因素的权值,绘制全国范围的TanDEM-X 90 m DEM误差绝对值分布图,且验证了可靠性。

Error Spatial Distribution Characteristics of TanDEM-X 90 m DEM over China

Some topographic factors such as slope, aspect, and land cover may cause errors on TanDEM-X 90 m Digital Elevation Model (DEM) product when collecting and processing of these data. In order to better understand the error distribution and serve the research in this field, the comparison between TanDEM-X 90 m DEM and ICESat/GLA14 DEM was conducted over the entire China. The findings are summarized: ① The average absolute error, Root Mean Square Error (RMSE) and Standard Deviation (STD) of TanDEM-X 90 m DEM over the entire China are about 3.89, 9.03, and 8.85 m, respectively. ② The error increases when the slope increases. The mean absolute error is about 1.29 m and the STD is about 2.84 m when the slope is below 3°. In comparison, the mean absolute error is above 20 m and the STD is about 30 m when the slope is above 25°. ③ For the aspect, the mean value of absolute error in the north-south direction is obviously smaller than that in the east-west direction, indicating the influence of aspect on TanDEM-X 90 m DEM product. ④ For the land cover, the uncultivated land shows the smallest error with the mean absolute error of 1.85 m, while the region covered with snow and glacier show the largest error with the mean absolute error of 12.68 m. Comparisons of the contour map and profile between TanDEM-X 90 m DEM and UAV-derived DEM suggest that the TanDEM-X 90 m DEM can reflect the real topography. However, due to the influence of resolution in some areas, it can not be expressed for some detailed terrains, especially for valley and ridge. The absolute error distribution of TanDEM-X 90 m DEM over the entire China is produced and evaluated based the weights of different influencing factors, which are considered to be reliable. Through the analysis of error distribution map, it is found that the accuracy of TanDEM-X 90 m DEM shows a trend of high in the north and low in the South over the entire mainland of China. In the North China region, the overall accuracy is higher, while the error in the northwest region is smaller, but the overall accuracy in the Central South region is poor. By referring to the relevant data, when using the data of TanDEM to generate DEM, its accuracy has a great relationship with the vegetation coverage rate of the area. High forest coverage rate will seriously affect the coherence of SAR data, and then affect the accuracy of generated DEM.