Refraction error depends on atmospheric conditions. It is generally considered to be about one-tenth of the curvature error.
The correct answer and explanation is:
Correct Answer: True
Refraction error depends on atmospheric conditions and is generally considered to be about one-tenth of the curvature error. This statement is true.
Explanation:
Refraction error occurs because light rays bend as they pass through the Earth’s atmosphere. This bending is due to the variation in air density, temperature, pressure, and humidity. These factors affect the refractive index of air. As a result, objects appear slightly displaced from their true position, especially when viewed over long distances or near the horizon.
In surveying and geodesy, refraction becomes significant when measuring long lines of sight, especially at low angles. It can cause errors in leveling and angular measurements. The atmosphere bends light downward, making a point appear higher than it actually is. This bending partially offsets the Earth’s curvature, which normally causes a target point to appear lower than it really is.
Curvature error results from the Earth’s spherical shape. Over a horizontal distance, the Earth’s surface curves away from a straight line of sight. The error from curvature increases with the square of the distance. For example, over one kilometer, the curvature error is approximately 7.85 centimeters.
Refraction compensates for a portion of this curvature. Empirically, refraction is often taken as one-seventh of the curvature, but a simplified and commonly accepted approximation is that refraction error is about one-tenth of the curvature error. This allows surveyors to apply a correction factor during measurements. The exact proportion can vary depending on atmospheric conditions, but for practical fieldwork, the one-tenth approximation provides a reasonable estimate.
Therefore, the statement is true because it aligns with standard surveying practice and scientific understanding of how atmospheric refraction interacts with the Earth’s curvature.