Why is the exact value of a measured angle or distance never known?

• A. Because every measurement contains an error due to natural, instrumental, and personal errors
• B. Because instruments are always wrong
• C. Because all data are made up
• D. Because surveying is unreliable

Answer: (D)

The main idea is that no measurement yields the exact true value. Every angle or distance you measure comes with some error, coming from natural variations in the environment, imperfections or miscalibration in the instrument, and the observer’s own reading or judgment. Because of these multiple, unavoidable sources of error, the true value can’t be known with perfect certainty. In practice we report what was measured and quantify the uncertainty, often by taking repeated measurements and using methods like least-squares adjustment to reduce errors and provide a best estimate with a measure of precision. This isn’t about surveying being unreliable or data being fake—it's about recognizing that measurements are inherently imperfect, and we manage that imperfection through careful technique and statistical analysis.