Optimized selection of key frames for monocular videogrammetric surveying of civil infrastructure

Videogrammetry is an inexpensive and easy-to-use technology for spatial 3D scene recovery. When applied to large scale civil infrastructure scenes, only a small percentage of the collected video frames are required to achieve robust results. However, choosing the right frames requires careful consideration. Videotaping a built infrastructure scene results in large video files filled with blurry, noisy, or redundant frames. This is due to frame rate to camera speed ratios that are often higher than necessary; camera and lens imperfections and limitations that result in imaging noise; and occasional jerky motions of the camera that result in motion blur; all of which can significantly affect the performance of the videogrammetric pipeline. To tackle these issues, this paper proposes a novel method for automating the selection of an optimized number of informative, high quality frames. According to this method, as the first step, blurred frames are removed using the thresholds determined based on a minimum level of frame quality required to obtain robust results. Then, an optimum number of key frames are selected from the remaining frames using the selection criteria devised by the authors. Experimental results show that the proposed method outperforms existing methods in terms of improved 3D reconstruction results, while maintaining the optimum number of extracted frames needed to generate high quality 3D point clouds.© 2012 Elsevier Ltd. All rights reserved.

Chthamalid cyprid identification - a photographic guide

A photographic guide to identification of the chthamalid cyprid larval stage of Chthamalus stellatus and Chthamalus montagui. Dimensions, shape, colour and distinctive features are highlighted.

Surveying nursing students on their sources of stress: A validation study

This study tested the psychometric properties of a questionnaire that measured sources of distress and eustress, or good stress, in nursing students. The Transactional model of stress construes stress in these different ways and is frequently used to understand sources of stress, coping and stress responses. Limited research has attempted to measure sources of distress and eustress or sources that can potentially enhance performance and well-being. A volunteer sample of final year nursing students (n = 120) was surveyed in the United Kingdom in 2007. The questionnaire measured sources of stress and measures of psychological well-being were taken to test construct validity. This was tested through an exploratory factor analysis. This reduced the questionnaire from 49 to 29 items and suggested three factors: learning and teaching, placement related and course organization; second, it was analysed by testing the assumptions of the Transactional model, the model on which the questionnaire was based. In line with the assumptions of the model, measures of distress related to adverse well-being, and measures of eustress related to healthier well-being responses. The test–retest reliability estimate was 0.8. While certain programme issues were associated with distress, placement-related experiences were the most important source of eustress.

Comparison of consumer perception and acceptability for steaks cooked to different endpoints: Validation of photographic approach

Photographs have been used to enhance consumer reporting of preference of meat doneness, however, the use of photographs has not been validated for this purpose. This study used standard cooking methods to produce steaks of five different degrees of doneness (rare medium, medium well, well done and very well done) to study the consumer’s perception of doneness, from both the external and internal surface of the cooked steak and also from corresponding photographs of each sample. Consumers evaluated each surface of the cooked steaks in relation to doneness for acceptability, ‘just about right’ and perception of doneness. Data were analysed using a split plot ANOVA and least significant test. Perception scores (for both external and internal surfaces) between different presentation methods (steak samples and corresponding photos), were not significantly different (p > 0.05). The result indicates that photographs can be used as a valid approach for assessing preference for meat doneness.

Assessing the Influence of Acoustic Variation on the Acquisition of Bathymetric Surveying Data

[author abstract] The field of hydrographic surveying is inherently important to achieving a true understanding of the world that underlies the vast bodies of water that cover the earth. In this study I will determine the uncertainties of depth estimates of the seafloor that relate to the survey design and sound velocity. The survey design and collection of sound velocity were all conducted of the coast of Vancouver Island, B.C. near the entrance of the Strait of Juan de Fuca. The assessment will show how the change in sound velocity over time will influence the bathymetric reading, if not corrected for. The differences in bathymetric depth readings will show a correlation to the changes in sound velocity.