I found toys at the beach and change at the park testing these expert-approved metal detectors

Scanning parks and beaches with one of these can be a unique and fascinating hobby.
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All About Monocular Cues and How We Use Them

Monocular cues are ways one eye judges distance, depth, and three-dimensional space. Six monocular cues guide depth perception: relative size, interposition, linear perspective, aerial perspective, ...