CET205 M5 Ktunotes.in

Surveying & Geomatics - Module 5 Overview

• Module 5 Topics:

  • Global Positioning System (GPS)

  • Remote Sensing

  • Geographic Information Systems (GIS)

Global Positioning System (GPS)

Introduction to GPS

• GPS is a satellite-based navigation system that allows for precise positioning on Earth.

• Early navigation methods included celestial navigation using celestial bodies as references.

Evolution of Navigation Techniques

• Celestial Navigation: Used for positioning in open waters based on sun, moon, and stars.

• Radio Navigation: Emerged in the mid-20th century using radio signals to determine distances.

  • Example: LORAN system providing longitude and latitude information, but not altitude.

Satellite-Based Navigation

• Satellite systems offer global coverage with three-dimensional positioning

• The Global Navigation Satellite System (GNSS) includes numerous satellites, ground stations, and user equipment, capable of producing location information with few meters of accuracy.

• GPS: The most known GNSS system, operational since 1978, consists of 24 satellites in orbit.

Components of GPS

Space Segment

• Contains at least 24 satellites positioned in a high Earth orbit of about 20,200 km.

• Satellites transmit radio signals to GPS receivers, maintaining precise time and orbital data.

Control Segment

• Monitors satellite positions and clock states.

• Comprises master control and uploading stations for correcting satellite data.

User Segment

• Comprises GPS receivers, which calculate positions based on received satellite signals.

• Receivers have varying capabilities based on the number of satellite signals they can process.

Working Principle of GPS

• GPS uses trilateration by measuring distances from at least three satellites.

• Types of Trilateration:

  • Two-dimensional trilateration involves determining location based on three reference points.

  • Three-dimensional trilateration requires four satellites for altitude determination.

• GPS signals are coded, allowing for both navigation and timing.

Differential GPS (DGPS)

• DGPS enhances accuracy by using a reference receiver at a known location to correct positional data of a moving receiver.

• Error Correction: Corrections are sent to the rover receiver for improved accuracy.

Applications of GPS

• Common in sectors like agriculture, transportation, military, disaster management, and construction.

• Provides real-time data used in GIS applications for spatial analysis.

Remote Sensing

Introduction to Remote Sensing

• Remote sensing involves gathering information from a distance, primarily using satellite imagery or aerial photography.

• Uses electromagnetic waves to observe, categorize, and analyze various Earth features and phenomena.

Energy Interactions in Remote Sensing

• Electromagnetic Spectrum: Includes visible light, infrared, microwave, and more.

  • Wavelength and frequency are essential for understanding energy sources.

• Energy interacts with the atmosphere and the target surface, which is crucial for accurate data acquisition.

Sensor Classification

• Passive Sensors: Measure naturally available energy (e.g., sunlight).

• Active Sensors: Emit their own energy to illuminate targets (e.g., RADAR).

Types of Sensors

• Multispectral Sensors: Capture data across multiple wavelengths.

• Hyperspectral Sensors: Collect data in numerous narrow spectral bands.

Applications of Remote Sensing

• Used for environmental monitoring, agriculture, urban planning, and disaster response.

Geographic Information Systems (GIS)

Introduction to GIS

• GIS is a system for managing and analyzing spatial data.

• Integrates hardware, software, data, people, and methods to solve geospatial problems.

Components of GIS

• Hardware: Computers, servers, GPS devices, scanners.

• Software: Applications for mapping, data analysis, and visualization (e.g., ArcGIS).

• Data: Geospatial data collected from surveys, satellite images, and existing datasets.

GIS Operations

1. Spatial Data Input

   • Collecting data through GPS, satellite imagery, or manual digitizing.

2. Attribute Data Management

   • Managing and verifying attribute data in tables.

3. Data Display

   • Creating maps and visualizations from analyzed data.

4. Data Exploration

   • Investigating data trends and relationships using visualization tools.

5. Data Analysis

   • Performing spatial analysis using GIS tools.

Data Models in GIS

• Vector Data Model: Represents geographic features as points, lines, and polygons.

• Raster Data Model: Represents area as grids of pixels, each having a specific value (e.g., satellite imagery).

Map Projections and Coordinate Systems

• Essential for translating Earth's 3D surface to a 2D representation.

• Different projections (e.g., cylindrical, conic, planar) serve various purposes based on application needs.

• Coordinate Systems: Geographic (longitude/latitude) and projected systems (e.g., UTM) allow for spatial analysis.