标题： 尼日利亚20米SPOT DEM的质量评估 显示英文标题

标题： Quality Assessment of the 20m SPOT DEM in Nigeria

摘要： 20米SPOT数字高程模型（Digital Elevation Model）由尼日利亚联邦测量师总署（OSGoF）获取，用于地形制图。由于众所周知全球数字高程模型的垂直精度在不同地貌环境中有所不同，因此需要对数字高程模型进行局部评估以验证其声明的精度。因此，本研究通过将数字高程模型的高度与拉各斯州和尼日利亚联邦首都特区（FCT）的780个地面控制点（GCPs）进行比较，评估了数字高程模型在不同土地覆盖类型中的质量。使用空间自相关分析和其他精度指标分析了高度差异的分布模式。在一般的精度评估中，数字高程模型在拉各斯的均方根误差为2.33米，在FCT为3.69米。结果显示，裸地上的高度在数字高程模型上表示得最准确，而建筑物区域的高度在两个地点都最不准确。尽管如此，尼日利亚不同土地覆盖类型中的SPOT数字高程模型精度超过了其声明的全球精度。拉各斯州低高度差异和高高度差异的空间分布显示出聚集性，而在FCT则相反。经过此次评估，建议该国应扩大数字高程模型的应用范围，以最大限度地发挥其效用。 显示英文摘要

摘要： The 20m SPOT DEM (Digital Elevation Model) was acquired by the Office of the Surveyor-General of the Federation (OSGoF) in Nigeria for use in topographic mapping. A localized assessment of the DEM is needed to validate its stated accuracies as it is well known that the vertical accuracy of global DEMs varies in different landscape contexts. Hence, this study assessed the quality of the DEM in variable land cover types by comparing its heights against 780 Ground Control Points (GCPs) in Lagos State and the Federal Capital Territory (FCT) of Nigeria. The pattern of distribution of the height differences was analysed using spatial autocorrelation analysis, including other accuracy metrics employed. In the general accuracy assessment, the DEM yielded root mean square errors of 2.33m in Lagos and 3.69m in the FCT. It was shown that heights over the bare lands were the most accurately represented on the DEM while heights over built-up areas are the least accurate at both locations. Despite this, the SPOT DEM accuracies in the varying land cover types surpassed its stated global accuracy. While the spatial distribution of low and high height differences in Lagos State showed clustering, the converse was the case in the FCT. Following this assessment, it is recommended that the country should extend the application scope of the DEM in order to exploit its utility to the maximum.