---
title: "Short note: Types of remote sensing"
subject: "Surveying II"
chapter: 7
key: "semester_4/surveying_ii:remote-sensing-types-application"
source: https://www.bctengineer.com/q/semester_4/surveying_ii/remote-sensing-types-application
site: BCT Engineering
---

# Short note: Types of remote sensing

Surveying II · Chapter 7: Photogrammetry and Remote Sensing

- Asked in: 2075 Baisakh, 4 marks; 2081 Chaitra, 4 marks (asked 2 times)
- Video: [Remote sensing//Advanced Surveying//Surveyor grade2](https://www.youtube.com/watch?v=BAgAAiKLARE) — CEekers
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/surveying_ii/remote-sensing-types-application
- Whole chapter: https://www.bctengineer.com/md/semester_4/surveying_ii/chapter-7

## Question

Write a short note on the types of remote sensing and its application.

## Short answer

Remote sensing is passive (sunlight, thermal) or active (radar, LiDAR), ground-, air- or spaceborne, and panchromatic/multispectral/hyperspectral. Applications in civil engineering include land use mapping, route selection, water resources, geology, disaster assessment, urban growth monitoring, environmental monitoring, and topographic survey.

## Answer

Remote sensing records information about the Earth's surface from a distance using electromagnetic energy.

#### Types of remote sensing
1. **By energy source**
   - **Passive:** uses natural energy, mainly reflected sunlight or emitted thermal radiation (e.g. Landsat, Sentinel-2, aerial photography).
   - **Active:** the sensor sends its own energy and records the return (e.g. radar/SAR, LiDAR).
2. **By platform:** ground-based, airborne (aircraft, drones) and spaceborne (satellites).
3. **By wavelength region:** visible and near-infrared, thermal infrared and microwave remote sensing.
4. **By number of bands:** panchromatic, multispectral and hyperspectral.

#### Applications
- **Land use and land cover mapping:** classification of urban, agricultural, forest and water areas from multispectral images.
- **Route and site selection:** alignment of roads, canals, pipelines and transmission lines, and choice of dam, bridge and airport sites using terrain, drainage and geology.
- **Water resources:** mapping of rivers, lakes and catchments; snow and glacier monitoring; flood extent and flood-plain mapping; watershed management.
- **Geology and soil:** identification of rock types, faults and lineaments, landslide-prone slopes and soil types for foundation and slope-stability studies.
- **Disaster management:** assessment of damage after earthquakes (e.g. Gorkha 2015), floods and landslides, and hazard mapping.
- **Urban planning:** monitoring of urban growth, infrastructure inventory, and change detection.
- **Environmental monitoring:** vegetation health, erosion, deforestation, pollution of water bodies, and impact assessment of projects.
- **Construction and survey:** topographic mapping, DEM and contour generation.

## Check yourself

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

1. What is the difference between passive and active remote sensing?
   A. Passive sends its own energy; active uses sunlight
   B. Passive uses natural energy; active sensor sends its own energy
   C. Passive is on ground; active is in space
   D. There is no difference
   Answer: B. Passive sensors use reflected sunlight or emitted radiation; active sensors send a signal and record the return. (Key point: Passive vs active)

2. Which pair is active remote sensing?
   A. Landsat and Sentinel-2
   B. Aerial photography and Landsat
   C. Thermal and optical cameras
   D. Radar/SAR and LiDAR
   Answer: D. Radar/SAR and LiDAR emit their own energy. (Key point: Examples)

3. Classification by number of bands gives:
   A. Visible, thermal, microwave
   B. Panchromatic, multispectral, hyperspectral
   C. Ground, airborne, spaceborne
   D. Active, passive
   Answer: B. Band number gives panchromatic, multispectral and hyperspectral; the others are other classifications. (Key point: Classification by bands)

4. Which is an application in civil engineering?
   A. Mixing concrete
   B. Testing steel strength
   C. Setting out a building
   D. Route and site selection for roads, canals and dams
   Answer: D. Terrain, drainage and geology from imagery guide alignment and site choice. (Key point: Application)

## Related in Surveying II

- [Remote sensing, types, applications](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Aremote-sensing-types-application-civil) — Surveying II, chapter 7, asked 3×
- [Short note: Remote sensing process, applications](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Aremote-sensing-process-applications) — Surveying II, chapter 7, asked 3×
- [Short note: Applications of remote sensing](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Aremote-sensing-applications) — Surveying II, chapter 7, asked 15×