--- title: "Working from whole to part; accuracy" subject: "Surveying I" chapter: 1 key: "semester_3/surveying_i:whole-to-part-and-accuracy" source: https://www.bctengineer.com/q/semester_3/surveying_i/whole-to-part-and-accuracy site: BCT Engineering --- # Working from whole to part; accuracy Surveying I · Chapter 1: Introduction - Asked in: 2079 Bhadra, 1+3 marks - Video: [Work from Whole to Part | Principal of Surveying | Surveying](https://www.youtube.com/watch?v=JPiP-N0eU1k) — Prof. Ankit Mahidadiya - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_3/surveying_i/whole-to-part-and-accuracy - Whole chapter: https://www.bctengineer.com/md/semester_3/surveying_i/chapter-1 ## Question What are the general principles of surveying? Why in surveying should the principles of "working from whole to part" and accuracy be followed? Explain. ## Short answer The principles are working from whole to part, fixing a point by at least two independent measurements, and checking every measurement. Working from whole to part prevents error accumulation by establishing a precise control framework first. Following required accuracy ensures reliable, economical results and detects blunders through checks. ## Answer #### General principles of surveying 1. **Working from whole to part.** 2. **Locating a new point by at least two independent measurements** (distances or angles) from points already fixed. 3. Check every measurement (take it twice or by another method) and keep the accuracy consistent with the purpose. #### Why work from whole to part? In this method a precise control framework is first fixed over the entire area, and the smaller details are then surveyed inside it by less precise methods. - Errors do not accumulate: each small part is tied to an already correct framework. - An error made in one part stays inside that part and does not affect the others. - The big triangles are measured accurately, so the plan fits the ground as a whole. - If we worked from part to whole, the small errors of each part would add up as we proceed, and the final survey would be distorted. Example: For a farm, big triangles such as ABC are measured accurately by chain; then the fields and buildings inside are fixed by offsets from the sides of the triangles. #### Why accuracy must be followed - A survey is used to design and set out works; wrong measurements cause a wrong layout, wasted cost and even failure of structures. - The final plan can only be as good as its measurements. On the other hand, there is no point in high accuracy where the purpose does not need it, so the required accuracy is decided first (e.g. 1 in 1000 for rough work, 1 in 5000 or better for good work). - Suitable instruments and methods are then selected to reach this accuracy economically. - Accuracy checks (closing error, repeated measurement) detect blunders before they spread. Hence, working from whole to part controls the errors, and working to the required accuracy makes the result reliable and economical. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Why is the 'working from whole to part' principle followed? A. It lets the details be measured with the most precise instruments B. It removes the need to check measurements C. Errors do not accumulate, and a mistake in one part stays inside that part D. It makes the survey cheaper because no control stations are required Answer: C. A precise control framework is fixed first and details are fitted inside it, so errors are localised instead of adding up. (Key point: Why whole to part) 2. In working from whole to part, what is done first? A. A precise control framework of a few widely spaced stations over the whole area B. Detail survey of each small part with offsets C. Plotting of the buildings and roads D. Small chain triangles with less precise methods Answer: A. The accurate control framework comes first; the details are surveyed inside it with less precise methods. (Key point: Order of work) 3. Why should the required accuracy be decided first? A. To avoid doing any checks B. To select instruments and methods that reach it economically C. To make all surveys use the highest accuracy D. To remove the need for control stations Answer: B. High accuracy is not needed everywhere; the purpose decides the accuracy and thus the methods. (Key point: Why accuracy) 4. What do accuracy checks such as closing error and repeated measurement do? A. Remove all random errors completely B. Replace the principle of whole to part C. Increase the scale of the map D. Detect blunders before they spread Answer: D. Checks catch mistakes early. 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