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Planetary topography measurement by descent stereophotogrammetry
Planetary and Space Science ( IF 2.4 ) Pub Date : 2021-05-04 , DOI: 10.1016/j.pss.2021.105242
G. Brydon , D.M. Persaud , G.H. Jones

Digital Terrain Models (DTMs) provide valuable insights into the nature of solar system surfaces, facilitating geological analysis, landing site selection and characterisation, and contextualising in situ measurements. For missions to solar system bodies for which orbiters and soft landed platforms are technologically or financially challenging to achieve, low mass descent or ascent probes (e.g. planetary penetrators) provide an alternative means by which to access the atmosphere and/or surface, and a platform from which to image the surface from a range of altitudes and perspectives. This paper presents a study into the concept of large-coverage descent stereophotogrammetry, whereby the stereo geometry of vertically offset wide-angle descent images is used to measure surface topography over a region of large extent. To do this, we simulate images of Mars' Gale Crater using a large coverage, high resolution DTM of the area, and derive topographic measurements by stereo matching pairs of simulated images. These topographic measurements are compared directly with the original DTM to characterise their accuracy, and dependence of elevation measurement accuracy on stereo geometry is thus investigated. For a stereo pair with a given altitude (corresponding to the altitude of its lower image), error in elevation measurement is found to have its minimum value for surface at a horizontal distance between 1 and 3 times the altitude. For a point on the surface with given horizontal distance from the imaging location, a stereo imaging altitude between 0.2 and 0.5 times this distance is found to achieve best elevation measurement accuracy. Surface appearance, and its change between two images of a stereo pair, is found to have a significant impact on stereo matching performance, limiting stereo baseline length to an optimum value range of 0.2–0.4 times the lower image's altitude, and resulting in the occurrence of occlusions and blind spots, particularly at oblique viewing angles.



中文翻译:

下降立体摄影测量法测量行星形貌

数字地形模型(DTM)可提供有关太阳系表面性质的宝贵见解,有助于进行地质分析,着陆点的选择和表征,以及现场测量的背景信息。对于要完成轨道技术和软着陆平台在技术或经济上具有挑战性的太阳系机构的飞行任务,低质量下降或上升探测器(例如行星穿透器)提供了进入大气层和/或地面的替代方法,以及一个平台从中可以从各种高度和角度对表面进行成像。本文介绍了对大范围下降立体摄影测量的概念的研究,其中垂直偏移的广角下降图像的立体几何用于在较大范围内测量表面形貌。去做这个,我们使用该区域的大覆盖率,高分辨率DTM来模拟火星大风火山口的图像,并通过对模拟图像进行立体匹配来得出地形测量结果。将这些地形测量结果与原始DTM直接进行比较,以表征其精度,从而研究了仰角测量精度对立体几何形状的依赖性。对于具有给定高度(对应于其下部图像的高度)的立体声对,在高度的1到3倍之间的水平距离处,高程测量误差被发现具有其最小值。对于与成像位置具有给定水平距离的表面上的点,发现在此距离的0.2到0.5倍之间的立体成像高度可以实现最佳的高程测量精度。表面外观

更新日期:2021-05-13
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