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Unequal atmospheric refraction due to high temperature comes under which sources of errors?
Personal
Natural
Instrumental
Personal and natural
Natural
Atmospheric refraction is a phenomenon caused by the variation in the density of the earth's atmosphere due to temperature, pressure, and humidity changes. Since these conditions are dictated by nature and are beyond the control of the surveyor, they are classified as natural sources of error.
Atmospheric refraction is a phenomenon caused by the variation in the density of the earth's atmosphere due to temperature, pressure, and humidity changes. Since these conditions are dictated by nature and are beyond the control of the surveyor, they are classified as natural sources of error.
hrefтАЛ=2R1тИТkтАЛтЛЕD2 тАФ Correction for refraction where k is the coefficient of refraction, R is the radius of the earth, and D is the distance.
╬┤=тИлn1тАЛтЛЕdhdnтАЛdh тАФ Basic integral expressing the angular deviation of a light ray in a stratified medium.
As light travels through layers of air with varying density, its path bends, causing a target observed via a theodolite to appear at an incorrect elevation. The index of refraction (n) of air depends on temperature (T) and pressure (P); thus, high temperatures cause thermal gradients (dT/dh), inducing refractive bending described by the curvature of light rays.
Errors in surveying are classified as Personal, Instrumental, or Natural.
Natural errors occur due to climatic conditions like temperature, wind, and gravity.
Refraction causes an error in vertical angles, which is critical in precise leveling and triangulation.
Correction for refraction is usually applied alongside Earth's curvature correction.
High temperature fluctuations create higher atmospheric density gradients, leading to 'shimmering' or 'boiling' of the image.
Predictable through standard atmospheric models.
Can be minimized by taking observations during specific hours of the day (e.g., early morning).
Cannot be eliminated by adjusting the instrument.
Fluctuates rapidly, making real-time compensation difficult.
Geodetic surveying
Precise leveling
Long-range trigonometric leveling
The refractive index of air n is typically close to 1.0003, but deviations occur based on air density.
Option A (Personal) refers to human limitations in reading scales or centering; Option C (Instrumental) refers to calibration errors like non-perpendicular axes.
B is correct тАФ Unequal atmospheric refraction is a natural phenomenon caused by variations in atmospheric density beyond human or instrumental control.
In exams, remember that any error caused by the environment (wind, sun, rain, refraction) is always classified as a 'Natural' error, regardless of the instrument used.
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