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  2. Horizon - Wikipedia

    en.wikipedia.org/wiki/Horizon

    For an observer standing on a hill or tower 100 metres (330 ft) above sea level, the horizon is at a distance of 36 kilometres (22 mi). For an observer standing on the roof of the Burj Khalifa, 828 metres (2,717 ft) from ground, and about 834 metres (2,736 ft) above sea level, the horizon is at a distance of 103 kilometres (64 mi).

  3. Tree height measurement - Wikipedia

    en.wikipedia.org/wiki/Tree_height_measurement

    Tree height is the vertical distance between the base of the tree and the tip of the highest branch on the tree, and is difficult to measure accurately. It is not the same as the length of the trunk. [note 1] If a tree is leaning, the trunk length may be greater than the height of the tree. The base of the tree is where the projection of the ...

  4. Snellen chart - Wikipedia

    en.wikipedia.org/wiki/Snellen_chart

    Snellen chart. Purpose. Snellen chart is used to estimate visual acuity (last three rows are 20/15, 20/13 and 20/10) A Snellen chart is an eye chart that can be used to measure visual acuity. Snellen charts are named after the Dutch ophthalmologist Herman Snellen who developed the chart in 1862 as a measurement tool for the acuity formula ...

  5. Average human height by country - Wikipedia

    en.wikipedia.org/wiki/Average_human_height_by...

    According to a study in France, executives and professionals are 2.6 centimetres (1.0 in) taller, and university students are 2.55 centimetres (1.0 in) taller than the national average. [ 7 ] As this case shows, data taken from a particular social group may not represent a total population in some countries.

  6. Human eye - Wikipedia

    en.wikipedia.org/wiki/Human_eye

    The sagittal vertical (height) of a human adult eye is approximately 23.7 mm (0.93 in), the transverse horizontal diameter (width) is 24.2 mm (0.95 in) and the axial anteroposterior size (depth) averages 22.0–24.8 mm (0.87–0.98 in) with no significant difference between sexes and age groups. [3]

  7. Human height - Wikipedia

    en.wikipedia.org/wiki/Human_height

    Human height or stature is the distance from the bottom of the feet to the top of the head in a human body, standing erect. It is measured using a stadiometer, [ 1 ] in centimetres when using the metric system or SI system, [ 2 ][ 3 ] or feet and inches when using United States customary units or the imperial system. [ 4 ][ 5 ] In the early ...

  8. Tree measurement - Wikipedia

    en.wikipedia.org/wiki/Tree_measurement

    This process applies the trigonometric tangent function. In this process the horizontal distance is measured to the trunk of a tree from a sighting position. The angle to the top of the tree is measured with the clinometer. horizontal distance at eye level to the tree trunk x tangent Θ = height above eye level.

  9. Visibility - Wikipedia

    en.wikipedia.org/wiki/Visibility

    At sea level, the Rayleigh atmosphere has an extinction coefficient of approximately 13.2 × 10 −6 m −1 at a wavelength of 520 nm. This means that in the cleanest possible atmosphere, visibility is limited to about 296 km. Visibility perception depends on several physical and visual factors.