Search

A novel concept of camera modelling for underwater 3D measurements based on stereo camera utilisation is introduced. The geometrical description of the ray course subject to refraction in underwater cameras is presented under assumption of conditions, which are typically satisfied or can be achieved approximately. Possibilities of simplification are shown, which allow an approximation of the ray course by classical pinhole modelling. It is shown how the expected measurement errors can be estimated, as well as its influence on the expected 3D measurement result. Final processing of the 3D measurement data according to the requirements regarding accuracy is performed using several kinds of refinement. For example, calibration parameters can be refined, or systematic errors can be decreased by subsequent compensation by suitable error correction functions. Experimental data of simulations and real measurements obtained by two different underwater 3D scanners are presented and discussed. If inverse image magnification is larger than about one hundred, remaining errors caused by refraction effects can be usually neglected and the classical pinhole model can be used for stereo camera-based underwater 3D measurement systems.

1. It has been shown that pure anhydrous glycerol and fatty triglycerides do not react appreciably below decomposition temperatures but that water or an alkaline material such as soap will catalyze reaction. 2. It has been shown that fatty monoglycerides when free from soap or alkaline material can be distilled in vacuum with only slight reversion in the higher members of the series. 3. The monoglycerides produced by the action of glycerol on methyl esters of fatty acids using caustic alkali as catalyst have been shown by periodic acid oxidation to have α-mono glyceride structure