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    基于SRTM3的MODIS图像几何精校正方法研究

    A method of highly accurate geometric correction for MODIS images based on SRTM3.

    • 摘要: 地形地物被高度综合化,只存在超大尺度或大尺度的特征地物,可供选择GCP(地面控制点)的明显地物非常有限,这是中低分辨率遥感图像进行几何精校正面临的最大难题。本文提出了基于SRTM3数据构建与遥感图像几何特征尺度一致的地理参照,对MODIS图像进行几何精校正的方法。首先,利用90 m分辨率的SRTM3进行地形综合,生成250 m像元尺度的DEM并提取地性线,并将其与1∶25万的大型湖泊、大江大河矢量图合并;使用地形光照立体渲染模型 (Hillshade)制作250 m的负立体可视化彩色地形地貌图;集成由3种地理信息要素构成的地理参照数据集。之后,分别选取250和500 m分辨率的MODIS数据,利用亚像元分解与增强技术制作125 m分辨率的假彩色影像。最后,叠加显示地理参照数据集和假彩色卫星图像,目视比对采集控制点,利用自适应三角网控制校正模型对多波段数据进行校正处理,其GCP点集的均方误差达到了431 m。结果表明:250 m分辨率的DEM地性线与MODIS亚像元图像表达的特征地物的几何尺度一致,MODIS图像中能识别的特征地物在SRTM3地性线与大型水系中均能找到,地性线所表达的特征地物点的数量多于遥感图像。与传统的基于基础地理底图选择控制点的方法相比,本文提出的方法更有利于同名地物点的判读和选取,并且操作处理简单,选取的GCP点的坐标精度较高,纠正处理工作效率高。

       

      Abstract: The features of terrain and ground surface are highly integrated and there are only some characteristic features with a super or large scale on the ground. Therefore, the potential obvious ground features that can be recognized and chosen as GCP are very limited. It is the biggest problem for lower and moderate resolution images to handle highly accurate geometric correction. In this paper,we present a method that creates the georeferencing data sets by using SRTM3 for GCP collecting for geometric correction,which can keep scale of the geometric elements consistent between satellite images and DEM. Firstly,the terrain synthesis needs to be done from SRTM3 with 90 m resolution to new DEM with 250 m pixels. Layers of terrain features extracted from 250 m DEM and the gorge features are merged into data sets of the borders of large lakes and big rivers from the 1:25 million map. And then,the visual negative relief color maps with 250 m are created by the terrain illumination and lighting model (Hillshade). Thus, the georeferencing data sets that include three kinds of geographic information elements are formed. Then multispectral bands from MODIS data sets with 250 m and 500 m resolution are selected and composited as pseudo color images with sub-pixel by decomposition and enhancement technology. Finally,maps of the georeferencing data sets and pseudo color images are overlaid and displayed on the same window for GCP collection by manual and visual comparison. All MODIS bands are subjected to highly accurate geometric correction by using a model of adaptive triangulation nets. As an example, it has 431 m of average square error for all GCP set. The results show that the geometric dimensions of 250 m of DEM are similar to features from MODIS sub-pixel images. The features that can be recognized and located on MODIS images will be found out and identified on the georeferencing data sets from SRTM3 or on the big scale maps of hydrology. The numbers of land features in the georeferencing data sets are more than in MODIS images. Compared with the traditional method that selects GCP from base maps, the method we propose is more suitable to interpret,identify and capture the same objects. And the operation and data processing is easy. It has higher accuracy of coordinates for capturing GCP and high working efficiency.

       

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