--- title: "Types of errors in surveying" subject: "Surveying I" chapter: 2 key: "semester_3/surveying_i:types-of-errors-surveying" source: https://www.bctengineer.com/q/semester_3/surveying_i/types-of-errors-surveying site: BCT Engineering --- # Types of errors in surveying Surveying I · Chapter 2: Distance Measurements - Asked in: 2075 Chaitra, 4 marks; 2064 Jestha, 6 marks; 2067 Asar, 4 marks (asked 3 times) - Video: [Types of Errors | Fundamental Concepts of Surveying | Geomatics Engineering - GATE](https://www.youtube.com/watch?v=GwEiyGxCXrc) — Ekeeda GATE & ESE - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_3/surveying_i/types-of-errors-surveying - Whole chapter: https://www.bctengineer.com/md/semester_3/surveying_i/chapter-2 ## Question Describe the various types of errors in surveying (differentiate errors and mistakes; cumulative and random/accidental errors) with examples. ## Short answer Mistakes are large, avoidable blunders. Errors are systematic (cumulative, same sign, correctable, e.g., tape too long) or accidental (random, compensating, reduced by averaging, e.g., reading fractions). They arise from personal, instrumental or natural sources. ## Answer An **error** is the difference between a measured value and its true value. No measurement is free from error. #### Mistakes (blunders) and errors | Mistake (blunder) | Error | |---|---| | Caused by carelessness or lack of knowledge | Caused by imperfect instruments, methods and nature | | Large in size, can be avoided | Small and unavoidable, but can be reduced | | Examples: wrong booking, miscounting tape lengths, reading 5.4 as 4.5 | Examples: tape expansion, reading estimate | | Found by checks and repeating | Corrected by calculation or adjusted | #### Types of errors **1. Cumulative (systematic) errors.** These have the same sign in all measurements and increase with the amount of work. Their size and sign can be found and a correction applied. - Examples: tape too long or short, a wrong zero in a levelling staff, sag, temperature change, collimation error in a theodolite. **2. Accidental (random or compensating) errors.** These occur due to causes beyond the surveyor's control and are equally likely to be positive or negative. They follow the laws of probability and are reduced by repeating the measurements and taking the mean. - Examples: estimating the last fraction of a reading, slight movement of the plumb bob, personal limitations of eyesight. #### By source - **Personal errors:** due to the observer (limited sight, bias, careless reading). - **Instrumental errors:** due to imperfect adjustment or construction of the instrument. - **Natural errors:** due to wind, temperature, refraction, curvature of the earth. Systematic errors are removed by calibration and corrections, and accidental errors are minimised by taking many observations. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. How does a mistake (blunder) differ from an error? A. A mistake is small and unavoidable B. A mistake comes from carelessness, is large and avoidable; an error is small from imperfect instruments or nature C. They are the same D. Mistakes follow probability laws Answer: B. Blunders are caused by carelessness and found by checks; errors come from instruments, methods and nature. (Key point: Mistake vs error) 2. Which statement about cumulative (systematic) errors is correct? A. Equally likely + or - B. Same sign in all measurements, so they grow with the work, but can be corrected by calculation C. Cannot be corrected D. Reduced only by averaging Answer: B. Their size and sign can be found, so a correction can be applied. (Key point: Cumulative errors) 3. How are accidental (random) errors reduced? A. By applying a fixed correction B. By repeating measurements and taking the mean C. By changing the tape D. They cannot be reduced Answer: B. They follow probability laws, so repeated observations and averaging minimise them. (Key point: Accidental errors) 4. Wind, refraction and temperature belong to which source of errors? A. Personal B. Instrumental C. Natural D. Blunders Answer: C. Natural errors arise from environmental conditions such as wind, temperature, refraction and curvature. (Key point: Classification by source) ## Related in Surveying I - [Sources of errors in chaining/taping](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aerrors-in-taping-sources-directions) — Surveying I, chapter 2, asked 4× - [Plane versus geodetic surveying](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aplane-vs-geodetic-surveying) — Surveying I, chapter 1, asked 5× - [Objectives of surveying; plane vs geodetic](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aobjectives-plane-geodetic) — Surveying I, chapter 1 - [EDM operation principles and errors](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aedm-operation-and-errors) — Surveying I, chapter 2, asked 2× - [Levelling methods; errors eliminated by balancing](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aprinciple-methods-leveling-balancing-sight) — Surveying I, chapter 5, asked 2× - [Face observation errors; optical theodolite](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aface-observation-errors-optical-theodolite) — Surveying I, chapter 7, asked 2× ## Related in other subjects - [File I/O operations, errors, random access](https://www.bctengineer.com/question.md?key=semester_1%2Fcomputer_programming%3Afile-io-errors-random-access) — Computer Programming, chapter 10 - [Random scan versus raster scan display](https://www.bctengineer.com/question.md?key=semester_5%2Fcomputer_graphics%3Arandom-vs-raster-display) — Computer Graphics, chapter 1, asked 7× - [Interpret: avoidable errors and use of words](https://www.bctengineer.com/question.md?key=semester_5%2Fcommunication_english%3Ainterpret-avoidable-errors-in-reasoning) — Communication English, chapter 1