A Novel Pixel-Level Image Matching Method for Mars Express HRSC Linear Pushbroom Imagery Using Approximate Orthophotos
A Novel Pixel-Level Image Matching Method for Mars Express HRSC Linear Pushbroom Imagery Using Approximate Orthophotos
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DOI：
10.3390/rs9121262
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发表时间：
2017-12
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影响因子：
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通讯作者：
X. Geng;Qing Xu;S. Xing;Chaozhen Lan;Junyi Xu
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文献类型：
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作者：
X. Geng;Qing Xu;S. Xing;Chaozhen Lan;Junyi Xu
火星地形数据，如数字正射影像图（DOM）和数字高程模型（DEM），是行星科学和探索任务的关键。我们研究的主要目的是使用火星快车（MEX）高分辨率立体相机（HRSC）生成更高分辨率的DEM。提出了一种新的HRSC线阵推扫式影像像素级匹配方法。我们建议首先对近似正射影像进行影像匹配。然后，将匹配点转换为原始图像进行前向相交。该方法采用了一些实用的策略，如分层图像匹配和归一化互相关（NCC）。这些战略的特点是：（1）在每一个金字塔层次上生成DEM和DOM;（2）使用当前金字塔层次上生成的DEM作为参考数据来生成下一个金字塔层次的近似正射影像;以及（3）使用正射影像的地面点坐标来估计共轭点的近似位置。因此，在影像校正过程中使用了精化后的DEM，近似正射影像上的共轭点的像素坐标位移将变得越来越小。四个实验数据集所获得的HRSC被用来验证所提出的方法。生成的DEM与HRSC 4级DEM产品进行了比较。实验结果表明，该方法可以生成精确的火星DEM。在原始图像分辨率水平下，可以以三个像素的精度来估计共辄点的近似位置。虽然观察到约两个像素的轻微系统误差，生成的DEM结果显示出良好的一致性与HRSC Level-4 DEM。
Mars topographic data, such as digital orthophoto maps (DOMs) and digital elevation models (DEMs) are essential to planetary science and exploration missions. The main objective of our study is to generate a higher resolution DEM using the Mars Express (MEX) High Resolution Stereo Camera (HRSC). This paper presents a novel pixel-level image matching method for HRSC linear pushbroom imagery. We suggest that image matching firstly be carried out on the approximate orthophotos. Then, the matched points are converted to the original images for forward intersection. The proposed method adopts some practical strategies such as hierarchical image matching and normalized cross-correlation (NCC). The characteristic strategies are: (1) the generation of a DEM and a DOM at each pyramid level; (2) the use of the generated DEM at the current pyramid level as reference data to generate approximate orthophotos at the next pyramid level; and (3) the use of the ground point coordinates of orthophotos to estimate the approximate positions of conjugate points. Hence, the refined DEM is used in the image rectification process, and pixel coordinate displacements of conjugate points on the approximate orthophotos will become smaller and smaller. Four experimental datasets acquired by the HRSC were used to verify the proposed method. The generated DEM was compared with the HRSC Level-4 DEM product. Experimental results demonstrate that an accurate and precise Mars DEM can be generated with the proposed method. The approximate positions of the conjugate points can be estimated with an accuracy of three pixels at the original image resolution level. Though slight systematic errors of about two pixels were observed, the generated DEM results show good consistency with the HRSC Level-4 DEM.