---
title: "GPS principle and components, GIS applications"
subject: "Surveying II"
chapter: 8
key: "semester_4/surveying_ii:gps-principle-gis-applications"
source: https://www.bctengineer.com/q/semester_4/surveying_ii/gps-principle-gis-applications
site: BCT Engineering
---

# GPS principle and components, GIS applications

Surveying II · Chapter 8: Field Astronomy and GPS

- Asked in: 2079 Chaitra, 2+2 marks; 2075 Bhadra, 4 marks (asked 2 times)
- Video: [Components Of GPS](https://www.youtube.com/watch?v=VfGLHUmNFKw) — OneFourFourExplains
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/surveying_ii/gps-principle-gis-applications
- Whole chapter: https://www.bctengineer.com/md/semester_4/surveying_ii/chapter-8

## Question

State the principle and components of GPS and mention the application of GIS.

## Short answer

GPS determines position by trilateration using travel time of signals from at least four satellites to solve for X,Y,Z and clock error. Its components are space segment (24+ satellites), control segment (monitoring stations), and user segment (receivers). GIS applications include land use planning, route alignment, utility mapping, disaster management, and environmental assessment.

## Answer

#### Principle of GPS
GPS measures the distance (pseudo-range) from the receiver to at least four satellites by the signal travel time, $\rho = c(t_r - t_s)$. As the positions of the satellites are known from the navigation message, the receiver position $(X, Y, Z)$ and its clock error are obtained by trilateration from four equations.

#### Components of GPS
1. **Space segment:** 24+ satellites in six orbital planes at about 20 200 km, sending L1 and L2 signals.
2. **Control segment:** master control and monitor stations that track the satellites and upload orbit and clock data.
3. **User segment:** the receivers used by surveyors and other users.

#### Applications of GIS
- Land use planning and urban planning; cadastral and land records.
- Route selection and site suitability analysis for roads, canals and dams.
- Utility mapping and management (water supply, sewers, power lines).
- Disaster management, flood and landslide hazard mapping.
- Water resources and watershed management; environmental impact assessment.
- Transport and traffic planning; infrastructure asset management.

## Check yourself

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

1. GPS position is found by:
   A. Triangulation angles
   B. Trilateration from distances to at least four satellites
   C. Compass
   D. Barometer
   Answer: B. Ranges from known satellite positions give X, Y, Z and clock error. (Key point: Principle)

2. The control segment:
   A. Is the receiver
   B. Launches rockets
   C. Draws maps
   D. Tracks satellites and uploads orbit and clock data
   Answer: D. Master and monitor stations. (Key point: Control segment)

3. Satellites send:
   A. Only visible light
   B. L1 and L2 signals
   C. Sound waves
   D. X-rays
   Answer: B. Carriers L1 and L2. (Key point: Signals)

4. A GIS application:
   A. Measuring concrete strength
   B. Pile driving
   C. Compass survey
   D. Site suitability analysis and utility mapping
   Answer: D. GIS is used for planning, utilities, disasters. (Key point: GIS application)

## Related in Surveying II

- [GPS principles, components, applications](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Agps-principles-components-applications) — Surveying II, chapter 8
- [Short note: GPS principle and components](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Agps-principle-components) — Surveying II, chapter 8, asked 19×
- [GPS, components and working principle](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Agps-components-working-principle) — Surveying II, chapter 8, asked 19×
- [Short note: Importance of GPS and GIS](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Agps-gis-importance) — Surveying II, chapter 8
- [Short note: GIS components and sub-systems](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Agis-components-subsystems) — Surveying II, chapter 10, asked 11×
- [Short note: GIS advantages and applications](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Agis-advantages-applications) — Surveying II, chapter 10

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