An efficient camera calibration technique offering robustness and accuracy over a wide range of lens distortion.

In the field of machine vision, camera calibration refers to the experimental determination of a set of parameters that describe the image formation process for a given analytical model of the machine vision system. Researchers working with low-cost digital cameras and off-the-shelf lenses generally favor camera calibration techniques that do not rely on specialized optical equipment, modifications to the hardware, or an a priori knowledge of the vision system. Most of the commonly used calibration techniques are based on the observation of a single 3-D target or multiple planar (2-D) targets with a large number of control points.

Laser scanning reveals bryophyte canopy structure.

We evaluated laser scanning as a method to provide depth measurements for bryophyte canopies at fine spatial scales to derive surface roughness (Lr), a structural parameter. Depths to the first vertical canopy contact were measured on 5 x 5 cm2 areas of 27 bryophyte canopies using a contact probe, a commercial laser scanner and a scanner employing a laser diode striper (LED scanner). Laser scanning adequately distinguished structural types, but scanner configuration led to differences in the magnitude of Lr.

Vertical impact increase in middle age may explain idiopathic weight-bearing joint osteoarthritis.

Objective: To test the hypothesis that ground reaction force increases when a standard stepping task is performed in late middle age.

Design: Consecutive sample.

Setting: Internal medicine practice.

Improving balance.

Objective: To test the hypothesis that shoes made with a sole material that retains compressed thickness between steps (low resiliency) provide balance better than and comfort equal to shoes composed of high resiliency sole material.

Setting: Older subjects were recruited from a medical clinic population, and younger subjects came from a recreational sports population.

Design: A randomized-order, cross-over, controlled comparison design.

Foot position awareness in younger and older men: the influence of footwear sole properties.

Objectives: To test the hypotheses that foot position awareness is related positively to stability, positively to shoe sole hardness, and negatively to shoe sole thickness, and that foot position awareness declines with advancing years.

Setting: Older subjects were consecutive volunteers from a medical clinic; younger subjects were volunteers from the community.

Design: Randomized-order, cross-over, controlled comparison.