Remote sensing of a gantry-equipped facility: Optimizing accuracy by integrating SfM photogrammetry and laserscan computer graphics through fixed base model geometry

Gantry-equipped facilities are used in a wide range of research fields, for instance geomorphology. Such setups allow for frequent and comprehensive measurements from sensors mounted on gantries or in fixed overhead position. These measurements often require high spatial and relative accuracy because of small scale morphology. Our objective is to develop high-performance data processing methods for our 20 by 3 m laboratory facility that is used for physical scale experiments on coastal morphology. We compare new and existing methods through quantification of spatial and relative errors in DEMs. Our new data processing methods incorporate SfM photogrammetry and computer graphics using a “base model” of our facility under idealized conditions. With this base model, we are able to successfully align all sensor outputs, creating large and geometrically consistent timeseries of orthomosaics and DEMs. Furthermore, the base model geometry provides for a gridded laserscan processing method, incorporating fixed extrinsic, intrinsic and distortion parameters of the sensors along the gantry. Compared to SfM photogrammetrically constructed DEMs, this new method shows greatly improved relative accuracy (0.74 mm compared to 0.97–4.18 mm) and spatial accuracy (2.13 mm compared to 2.39–8.25 mm). Moreover, we show that variations of extrinsic parameters of laserscan equipment along the gantry survey are significant, while these parameters are often assumed to be constant. Our improved methods may open up new research questions in experimental geomorphology and can be applied to other facilities, research fields and industries. • New and known DEM construction methods of a gantry-equipped facility are compared. • Some methods involve an SfM photogrammetric base model of our facility. • Base model alignment is fast and consistent for large timeseries and low overlap. • The most accurate DEM method is base model geometry-based laserscan processing. • We recommend our methods to other facilities and applications.