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Surveying and Geomatics: Measurement errors and adjustments · Types of Errors

How surveyors tell blunders, systematic errors and random errors apart, where each comes from, and how each is caught or corrected.

Surveying and Geomatics · 34 questions

Try 3 questions

1. A surveyor measures 125.37 m but writes 152.37 m in the field book. What kind of error is this?

  1. A systematic error
  2. A blunder
  3. A random error
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Answer: A blunder

Blunders are human mistakes such as transposed digits; they follow no pattern and must be caught by checks, not modeled statistically.

2. A tape is 3 mm too long. A line measured as 9 full tape lengths will read about how far off?

  1. 27 mm too short
  2. 9 mm too short
  3. 27 mm too long
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Answer: 27 mm too short

A long tape covers more ground than it reports, so each length is under-read by 3 mm, and a systematic error adds up: 9 × 3 mm = 27 mm.

3. When many independent measurements with random errors are added together, how does the total random error grow?

  1. With the square root of their number
  2. In direct proportion to their number
  3. Not at all, since they cancel exactly
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Answer: With the square root of their number

Random errors have random signs and partly cancel; their variances add, so the standard error of a sum of n equal parts is σ√n.

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