Camera Calibration for Coastal Monitoring Using Available Snapshot Images

Abstract

Joint intrinsic and extrinsic calibration from a single snapshot is a common requirement in coastal monitoring practice. This work analyzes the influence of different aspects, such as the distribution of Ground Control Points (GCPs) or the image obliquity, on the quality of the calibration for two different mathematical models (one being a simplification of the other). The performance of the two models is assessed using extensive laboratory data (i.e., snapshots of a grid). While both models are able to properly adjust the GCPs, the simpler model gives a better overall performance when the GCPs are not well distributed over the image. Furthermore, the simpler model allows for better recovery of the camera position and orientation.

The Influence of Camera Calibration on Nearshore Bathymetry Estimation from UAV Videos

“…This figure also shows the distribution of the intrinsic parameters obtained, for checking purposes, from the 30 aforementioned images of each video. The distributions are, in general, compact, showing that the number and distribution of the GCPs allow for a potentially good calibration of the camera, according to [43]. Besides, the results for the different values of n I are similar and centered in the distribution (for n I = 1 by chance).…”

“…The influence of the governing Equation 3, which includes the intrinsic parameters, has also been analyzed. When dealing with video monitoring images, where the GCPs are often scarce and not well distributed along the image, some reasonable simplifications of the model have shown to work more robustly for some cameras [43]. Three different simplifications have been considered here:…”

UCalib: Cameras Autocalibration on Coastal Video Monitoring Systems

“…Equation (1) represents a reasonable simplification of more complex distortion models: the radial distortion was assumed parabolic and tangential distortion neglected. This simplified model was shown to be able to model the distortion of common cameras [39] and, in particular, the cameras considered in this work. The eight free parameters of the model are the camera position, x c = (x c , y c , z c ) , the three eulerian angles (φ, σ and τ), as well as k 1 and s.…”