High-accuracy UAV photogrammetry of ice sheet dynamics with no ground control
High-accuracy UAV photogrammetry of ice sheet dynamics with no ground control
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DOI：
10.5194/tc-13-955-2019
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发表时间：
2019-03-19
期刊：
影响因子：
5.2
通讯作者：
Snooke, Neal
中科院分区：
文献类型：
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作者：
Chudley, Thomas R.;Christoffersen, Poul;Snooke, Neal
无人机（uav）和多视点立体运动结构（SfM-MVS）摄影测量技术在地球科学应用中越来越普遍，但在缺乏密集和分布良好的地面控制点（gcp）网络的情况下，最终产品的精度可能会大大降低。这在难以接近或危险的野外环境中是有问题的，包括高度裂缝的冰川，在那里实施合适的GCP网络在后勤上是困难的，如果不是不可能的话。为了克服这一挑战，我们提出了一种替代的地理定位方法，称为gnss支持的空中三角测量（GNSS-AT）。在这里，使用机载载波相位GNSS接收器来确定使用运动学差分载波相位定位的照片采集位置。相机位置可以用作摄影测量过程的地理空间输入。我们描述了这种方法在低成本、定制的无人机上的实现，并将该方法应用于格陵兰岛西部Store冰川的冰川环境。我们在产犊前沿验证了该技术，当飞行高度接近地面450米时，地形不确定性水平为+/- 0.12米（类似于1.1倍地面采样距离），垂直为+/- 0.14米（类似于1.3倍地面采样距离）。这与以前在冰川环境中由gcp得出的不确定性相比是有利的，并允许我们在内陆研究地点应用SfM-MVS摄影测量，那里的冰流量为每天2米（-1），并且无法获得稳定的地面控制。在这里，我们能够在不使用gcp的情况下，第一次用无人机获得冰盖内部的速度场。鉴于在冰川学和地球科学中越来越多地使用无人机和sbm - mvs， GNSS-AT将对那些希望在GCP收集受到物流限制的情况下使用无人机摄影测量来获得高精度地形变化测量的人感兴趣。
Unmanned aerial vehicles (UAVs) and structure from motion with multi-view stereo (SfM-MVS) photogrammetry are increasingly common tools for geoscience applications, but final product accuracy can be significantly diminished in the absence of a dense and well-distributed network of ground control points (GCPs). This is problematic in inaccessible or hazardous field environments, including highly crevassed glaciers, where implementing suitable GCP networks would be logistically difficult if not impossible. To overcome this challenge, we present an alternative geolocation approach known as GNSS-supported aerial triangulation (GNSS-AT). Here, an on-board carrier-phase GNSS receiver is used to determine the location of photo acquisitions using kinematic differential carrier-phase positioning. The camera positions can be used as the geospatial input to the photogrammetry process. We describe the implementation of this method in a low-cost, custom-built UAV and apply the method in a glaciological setting at Store Glacier in western Greenland. We validate the technique at the calving front, achieving topographic uncertainties of +/- 0.12 m horizontally (similar to 1.1 x the ground sampling distance) and +/- 0.14 m vertically (similar to 1.3 x the ground sampling distance), when flying at an altitude of similar to 450 m above ground level. This compares favourably with previous GCP-derived uncertainties in glacial environments and allows us to apply the SfM-MVS photogrammetry at an inland study site where ice flows at 2 m day(-1) and stable ground control is not available. Here, we were able to produce, without the use of GCPs, the first UAV-derived velocity fields of an ice sheet interior. Given the growing use of UAVs and SfM-MVS in glaciology and the geosciences, GNSS-AT will be of interest to those wishing to use UAV photogrammetry to obtain high-precision measurements of topographic change in contexts where GCP collection is logistically constrained.