Remote Sensing (RS)
Definition:
Remote sensing is the science of obtaining information about objects or areas from a distance, typically using satellites or aircraft.
How it works:
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Uses electromagnetic radiation (EMR)
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Sensors detect reflected/emitted radiation from Earth's surface
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Data is analyzed for mapping, monitoring, etc.
Types:
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Passive Remote Sensing: Uses natural energy (e.g., sunlight) – e.g., Landsat
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Active Remote Sensing: Uses artificial signals (e.g., RADAR, LiDAR)
Applications:
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Weather forecasting
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Agriculture
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Forest cover mapping
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Disaster management
Important Terms:
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Sensor: Device that collects data (e.g., radiometer)
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Resolution: Spatial, spectral, temporal, radiometric
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Platform: Aircraft, satellite, drone
📘 2. GIS (Geographic Information System)
Definition:
GIS is a system designed to capture, store, manipulate, analyze, manage, and present spatial or geographic data.
Components:
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Hardware
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Software (e.g., ArcGIS, QGIS)
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Data (raster & vector)
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People & methods
Functions:
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Mapping
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Spatial analysis
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Data management
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Geocoding
Applications:
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Urban planning
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Transportation
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Environmental studies
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Resource management
📘 3. GPS (Global Positioning System)
Definition:
GPS is a satellite-based navigation system that provides location and time information anywhere on Earth.
How GPS Works:
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24+ satellites in orbit (NAVSTAR)
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A GPS receiver calculates position using signals from at least 4 satellites
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Uses trilateration technique
Applications:
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Navigation
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Surveying
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Disaster response
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Wildlife tracking
📘 4. DGPS (Differential GPS)
Definition:
An enhanced version of GPS that improves location accuracy using a fixed ground-based reference station.
How DGPS Works:
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One GPS receiver at known location (base station)
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Another GPS receiver (rover) nearby
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Corrections sent from base to rover
Accuracy:
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Up to 10 cm
📘 5. ETS (Electronic Total Station)
Definition:
ETS is an optical/electronic instrument used in modern surveying that integrates an electronic theodolite, EDM (Electronic Distance Measurement), and software.
Functions:
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Measures angles & distances
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Calculates coordinates
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Stores data electronically
Applications:
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Civil engineering
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Construction
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Land surveying
🌍 6. Types of Satellites by Purpose
| Type | Use Example |
|---|---|
| Weather Satellite | INSAT, NOAA |
| Earth Observation | Landsat, Resourcesat |
| Communication | GSAT, INTELSAT |
| Navigation | GPS (USA), GLONASS (Russia) |
| Scientific | Hubble Space Telescope |
| Military | Reconnaissance satellites |
🚀 7. Space Programs of Different Countries
| Country | Space Agency | Important Satellites/Programs |
|---|---|---|
| India | ISRO | Chandrayaan, Mangalyaan, Cartosat, RISAT |
| USA | NASA | Landsat, Hubble, GPS, Artemis |
| Russia | Roscosmos | GLONASS, Luna missions |
| China | CNSA | BeiDou, Tianwen-1, Chang’e missions |
| EU (ESA) | European Space Agency | Sentinel (Copernicus Program) |
| Japan | JAXA | Himawari, Hayabusa |
| France | CNES | SPOT series |
| UAE | UAESA | Hope Mars Mission |
✅ Important Points Summary
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Remote sensing uses satellite/airborne sensors to study Earth.
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GIS integrates spatial & attribute data for analysis.
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GPS uses 24+ satellites for accurate location.
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DGPS uses correction signals to improve GPS accuracy.
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ETS is used for surveying with electronic angle/distance measurement.
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ISRO is India's space agency with notable missions like Chandrayaan and Mangalyaan.
❓ MCQs with Answers
Q1. What does GPS stand for?
A. Global Position Sensor
B. General Positioning System
C. Global Positioning System ✅
D. Ground Position Setup
Q2. Which of the following is a passive remote sensing method?
A. RADAR
B. LiDAR
C. Optical satellite imaging ✅
D. SONAR
Q3. ETS is used in which field?
A. Space science
B. Land surveying ✅
C. Meteorology
D. Oceanography
Q4. Which Indian satellite is used for earth observation?
A. GSAT
B. Cartosat ✅
C. INSAT
D. Aryabhata
Q5. DGPS provides better accuracy than GPS by using:
A. More satellites
B. Laser technology
C. Base station corrections ✅
D. Infrared signals
Q6. ISRO launched which Mars mission?
A. Chandrayaan
B. PSLV
C. Mangalyaan ✅
D. Aryabhata