Positive error is caused if

📈 Understanding Positive Error

In surveying, an error is the difference between a measured value and the true value. A positive error occurs when the measured distance is greater than the true distance. This means the corresponding correction that needs to be applied is negative (subtractive) to get the true value.

True Distance = Measured Distance - Positive Error

🔬 Detailed Analysis of Causes

Let's analyze why each of the given situations results in a positive error:

• A. Length of the chain is shorter than the standard: If a chain is too short (e.g., a 20m chain is actually 19.9m), you are using a faulty, shorter measuring stick. Over a distance, you will count more "chain lengths" than actually exist, leading to a recorded measurement that is longer than the true distance.
• B. Slope and sag corrections are not applied: The measured length along a slope or a sagging chain is always longer than the true horizontal distance. Corrections for slope and sag are therefore always subtractive (negative corrections). If you fail to apply these corrections, your measured length remains inflated, hence a positive error.
• C. Measurements are made along an incorrectly aligned line: The shortest distance between two points is a straight line. If you measure along a crooked or misaligned path, the distance you record will always be longer than the true, straight-line distance.

📊 Summary: Causes of Positive vs. Negative Errors

💡 Key Takeaway

Since all three scenarios—using a short chain, neglecting slope/sag corrections, and measuring along a misaligned line—result in a measured distance that is greater than the true distance, they all cause a positive error. Therefore, all options are correct.