Development of a comprehensive model for concurrent water surface and bottom reconstruction in photo bathymetry (PhotoBathyWave)

在摄影测深学中，摄影测量技术用于通过水面拍摄的陆地和航空图像对水底地形进行三维测量。不同光学介质环境下的几何建模必须根据斯涅尔定律考虑像射线的折射。这要求存在分离光学介质的界面的精确几何模型。如果图像是在自由流动的水面上拍摄的，波浪的存在严重阻碍了几何建模。到目前为止，这个任务只存在近似解。该项目的目标是开发一种通用和通用的方法，通过开放的动态波浪影响水面进行多媒体摄影测量。我们的目标是在一个综合摄影测量参数估计程序中，同时从多视图图像中确定水面形状和淹没的水底地形。这就需要利用固定水面的折射或反射特性对其进行时空建模，作为严格考虑多射线空间相交光路折射的基础，从而精确地确定无偏的水底坐标。为了避免过度参数化，将特别强调参数确定性，其中包括适当的随机建模和测量配置的规划。一般来说，这将在扩展束块调整或解耦处理框架中同时确定图像方向和水面和底部点坐标的综合方法中得到解决。虽然存在大量文献用于用基于图像的技术对水面或底部几何形状进行建模，但我们的目标是从相同的立体图像中估计两者。在光测深处理管道中考虑复杂的、受动态波浪影响的水面是一种创新的方法，它有可能(i)将精度水平大幅提高一个数量级，并（ii）大大扩展光测深的应用领域。研究成果的应用领域包括水文生态学和水文形态学、海岸带的航空测绘、内陆浅水水体的无人机测绘、珊瑚礁变化探测或水力学实验室通道设施的多种测量任务。

In photo bathymetry, photogrammetric techniques are used for 3D measurements of water bottom topography from terrestrial and aerial images taken through water surfaces. Geometric modelling in environments with different optical media must consider image ray refraction according to Snell’s Law. This requires the existence of a precise geometric model of the interface separating the optical media. If images are taken through a free-flowing water surface, the presence of waves severely impedes geometric modelling. So far, only approximate solutions exist for this task. The objective of the proposed project is to develop a generic and versatile approach for multimedia photogrammetry through open dynamic wave-affected water surfaces. Our goal is to simultaneously determine both the shape of the water surface and the submerged water bottom topography from multi-view images in an integrated photogrammetric parameter estimation procedure. This necessitates spatio-temporal modelling of an instationary water surface exploiting its refractive or reflective property as a basis for strict consideration of refraction on the optical paths in multi-ray spatial intersection for precise unbiased water bottom coordinate determination. Special emphasis will be laid on parameter determinability in order to avoid over-parametrization, which includes appropriate stochastic modelling and planning of the measurement configuration. In general, this will be addressed in an integrated approach for simultaneously determining image orientations and water surface and bottom point coordinates within an extended bundle block adjustment or in a decoupled processing framework.While a broad body of literature exists for modelling either water surface or bottom geometry with image based techniques, our aim is to estimate both from the same stereo images. The consideration of complex, dynamic wave effected water surfaces in photo bathymetry processing pipelines constitutes an innovative approach, which has the potential (i) to substantially raise the accuracy level by one order of magnitude and to (ii) considerably extend the application fields of photo bathymetry. Application fields benefiting from the research outcomes include hydroecology and hydromorphology, airborne mapping of coastal zones, UAV-based mapping of shallow inland water bodies, coral reef change detection, or manifold measurement tasks in hydromechanical laboratory channel facilities.