High-Speed Motion Picture Photography Analysis in 3D - A New Approach to Analyzing Full Scale Blasts

Vanderberg B,
Organization: The Australasian Institute of Mining and Metallurgy
Pages: 6
Publication Date: Jan 1, 1990
A 3D, PC based computer program is currently under development by Blasting Analysis International, Inc., to analyze the kinetics of full scale blasts with two or more high-speed motion picture cameras. Todays common approach of utilizing only a single camera system can, in some cases, lead to great errors and erroneous conclusions when motion is assumed to be in a predefined plane of motion. CMe phrase, "What you see is what you get, it no longer true in 3D."). This is especially true in blasting environments which exhibit complex and/or predominant structural geology. The 3D system eliminates this problem, and includes automatic corrections for vertical and horizontal camera optic axis orientation, dimensional controls, lens distortion, field set-ups, projection imaging and digitized inputs. The only information required is the surveyed or known coordinates of at least six non coplanar points in the field of view. Motitn from each camera view is then digitized, transformed through a direct linear transformation, and processed with the 3D software, which also automatically time matches the data, even when the high-speed cameras are operated at different speeds. Eleven calibration constants are generated using an overdetermined system of linear equations to output the true 3D coordinates of motion in the time domain. Applications for this 3D approach are not restricted to just analyzing the kinetics of a blast. The system is sufficiently flexible to allow an accurate, quick and economical method of bench face profile analysis, generate muck pile profiles and estimate volumetric calculations. The recording systems for these applications can be common 35mm still photography and/or video equipment. It is envisioned that this system will soon replace expensive laser surveying systems at a fraction of the cost in the near future. It is also an excellent system to accurately quantify drill pattern layouts and the spatial locations of each blasthole. This information is required for generating single hole based synthetic seismograms to accurately predict the vibrational outputs of full scale blasts. In terms of litigation concerning claims resulting from blast induced ground vibrations to structures, the system is proving to be an excellent and economical method of performing pre-blast surveys where differential settlement is suspect.
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