---
title: "Criteria for selecting a suitable scale"
subject: "Surveying I"
chapter: 1
key: "semester_3/surveying_i:criteria-selecting-scale"
source: https://www.bctengineer.com/q/semester_3/surveying_i/criteria-selecting-scale
site: BCT Engineering
---

# Criteria for selecting a suitable scale

Surveying I · Chapter 1: Introduction

- Asked in: 2076 Chaitra, 2 marks; 2074 Chaitra, 2 marks (asked 2 times)
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/surveying_i/criteria-selecting-scale
- Whole chapter: https://www.bctengineer.com/md/semester_3/surveying_i/chapter-1

## Question

What are the selection criteria of scale for drawing a map? Explain.

## Short answer

Scale choice depends on purpose (large scale for detail, small for overview), area extent, accuracy (smallest plottable 0.25 mm), detail amount, drawing sheet size, cost, and readability. For example, 1:500 for building plans, 1:25,000 for topographic maps.

## Answer

The scale of a map should be chosen after considering the following points:

1. **Purpose of the map.** Detailed engineering plans (building, road design) need a large scale such as 1:100 to 1:1000; reconnaissance or index maps use a small scale such as 1:50,000.
2. **Extent of the area.** A large area drawn at a large scale needs huge drawing sheets; the scale must let the area fit on a convenient sheet.
3. **Accuracy and the smallest plottable length.** The smallest length that can be plotted is about 0.25 mm. The ground length represented by 0.25 mm (0.25 mm $\times$ scale denominator) must not be more than the required ground accuracy. For an accuracy of 0.1 m, the scale cannot be smaller than 1:400.
4. **Amount of detail** to be shown. More detail needs a larger scale.
5. **Size of the drawing sheet** and ease of handling and storage.
6. **Cost and time.** A larger scale means more field work, cost and time.
7. **Convenience of reading.** Round RFs (1:500, 1:1000, 1:2500) make plotting and reading easy.
8. **Standards of the department**, e.g. the Survey Department of Nepal uses 1:500 to 1:2500 for cadastral maps and 1:25,000 for topographic maps.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which scale suits a detailed engineering plan of a building or road design?
   A. A small scale such as 1:50,000
   B. A large scale such as 1:100 to 1:1000
   C. 1:250,000
   D. Any scale, as purpose does not matter
   Answer: B. Detailed engineering plans need large scales; small scales are used for reconnaissance or index maps. (Key point: Purpose)

2. How does the amount of detail affect the scale chosen?
   A. More detail calls for a smaller scale
   B. It has no effect
   C. More detail calls for a larger scale
   D. Detail only affects the paper colour
   Answer: C. A large scale is needed to show more details clearly. (Key point: Amount of detail)

## Related in Surveying I

- [Diagonal scale: Kathmandu-Pokhara highway map](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Adiagonal-scale-kathmandu-pokhara-224) — Surveying I, chapter 1, asked 2×
- [Scale of a map and its classification](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Ascale-of-map-classification) — Surveying I, chapter 1
- [Scale for 1.5 km road on map](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Ascale-road-1-5-km) — Surveying I, chapter 1
- [RF and scale for 51072 m² plot](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Ascale-plot-51072-sqm) — Surveying I, chapter 1, asked 3×
- [RF and scale for 6.304 ha plot](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Ascale-plot-6-304-ha) — Surveying I, chapter 1, asked 3×
- [RF and scale for 51750 m² plot](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Ascale-plot-51750-sqm) — Surveying I, chapter 1, asked 3×

## Related in other subjects

- [Criteria for selecting a processor](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Aprocessor-selection-criteria) — Embedded System, chapter 2, asked 2×
- [Criteria for selecting a water source](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Aselection-criteria-water-source) — Water Supply Engineering, chapter 2, asked 5×
- [Flying height from photo and map scale](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Aflying-height-pq-20cm-focal-24) — Surveying II, chapter 7
- [Selection criteria for ADC](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Aadc-selection-criteria) — Instrumentation II, chapter 4, asked 3×