---
title: "Plane versus geodetic surveying"
subject: "Surveying I"
chapter: 1
key: "semester_3/surveying_i:plane-vs-geodetic-surveying"
source: https://www.bctengineer.com/q/semester_3/surveying_i/plane-vs-geodetic-surveying
site: BCT Engineering
---

# Plane versus geodetic surveying

Surveying I · Chapter 1: Introduction

- Asked in: 2070 Chaitra (old course), 4 marks; 2069 Chaitra, 4 marks; 2068 Chaitra, 2 marks; 2062 Poush, 4 marks; 2078 Kartik, 1+3 marks (asked 5 times)
- Video: [Difference between Plane Surveying & Geodetic Surveying](https://www.youtube.com/watch?v=FCB3Fi4tIuw) — Learn Civil Tech & Tricks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/surveying_i/plane-vs-geodetic-surveying
- Whole chapter: https://www.bctengineer.com/md/semester_3/surveying_i/chapter-1

## Question

Define surveying. Differentiate between plane surveying and geodetic surveying.

## Short answer

Surveying determines relative positions of points and maps them. Plane surveying neglects earth's curvature for areas up to about 250 km², using plane trigonometry and ordinary accuracy. Geodetic surveying considers curvature for larger areas, uses spherical trigonometry, and attains high precision.

## Answer

**Surveying** is the art and science of determining the relative positions of points on, above or below the earth's surface by measuring distances, directions (angles) and elevations, and of representing them on a map or plan to a suitable scale. It is also used to set out (locate) planned works on the ground.

#### Difference between plane and geodetic surveying

| Basis | Plane surveying | Geodetic surveying |
|---|---|---|
| Shape of earth | Taken as a plane; curvature neglected | Earth taken as a spheroid; curvature considered |
| Level surface | Treated as a straight line | Treated as a curved line (arc) |
| Area covered | Small, up to about 250 km$^2$ | Large, above about 250 km$^2$ |
| Triangle angles | Sum is exactly $180^\circ$ | Sum exceeds $180^\circ$ (spherical excess) |
| Mathematics | Plane trigonometry | Spherical trigonometry |
| Accuracy | Ordinary accuracy | High accuracy; precise instruments |
| Purpose | Local works: roads, buildings, canals | Control points, national mapping, large projects |
| Cost and time | Low | High, needs skilled staff |
| Geodetic data | Not needed | Latitude, longitude and azimuth are determined |

In short, the two methods differ in whether the earth's curvature is considered or neglected; this depends on the size of the area and the accuracy required.

## Check yourself

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

1. Surveying is best defined as
   A. measuring only the areas of land for taxation
   B. determining relative positions of points by measuring distances, directions and elevations and representing them on a map or plan
   C. drawing maps from aerial photographs only
   D. measuring the earth's shape without plotting
   Answer: B. Surveying is the art and science of finding relative positions of points and plotting them to scale, as well as setting out works. (Key point: Definition)

2. What is the basic difference between plane and geodetic surveying?
   A. The type of chain used
   B. Whether levelling is done
   C. Whether the earth's curvature is neglected or considered
   D. Whether the survey is done on land or water
   Answer: C. Plane surveying neglects curvature, geodetic considers it; this depends on area and accuracy needed. (Key point: Basic difference)

3. Which row is correct for geodetic surveying?
   A. Spherical trigonometry, high accuracy, area above about 250 km^2
   B. Plane trigonometry, low cost, area below 250 km^2
   C. Spherical trigonometry, low accuracy, small area
   D. Plane trigonometry, high accuracy, large area
   Answer: A. Geodetic surveying uses spherical trigonometry, precise instruments and covers large areas. (Key point: Comparison)

## Related in Surveying I

- [Objectives of surveying; plane vs geodetic](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aobjectives-plane-geodetic) — Surveying I, chapter 1
- [Plane and geodetic surveying; principles](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aplane-geodetic-and-principles) — Surveying I, chapter 1, asked 7×
- [Classification of surveying](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aclassification-of-surveying) — Surveying I, chapter 1, asked 4×
- [Intersection versus resection in plane tabling](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aintersection-vs-resection-plane-table) — Surveying I, chapter 6

## Related in other subjects

- [Plane stress versus plane strain](https://www.bctengineer.com/question.md?key=semester_8%2Fcomputational_techniques_in_civil_engineering%3Aplane-stress-vs-plane-strain) — Computational Techniques in Civil Engineering, chapter 3, asked 4×
- [Plane failure versus wedge failure](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aplane-failure-versus-wedge-failure) — Engineering Geology I, chapter 6