Lecture No. 10 Remote Sensing 2

Overview of Remote Sensing

  • Course Title: Remote Sensing-II (GEO INFORMATICS CE4131)

  • Lecturer: Engr. M. Wajahat Ali Khawaja

  • Email: wajahat.ali@cust.edu.pk

Introduction to Remote Sensing

Definition

  • Remote sensing is the process of recording electromagnetic energy from a distance using instruments.

Key Components

  • Remote Sensing Platforms: The structures (vehicles) used to carry sensors.

  • Remote Sensing Sensors: Devices that detect and record electromagnetic energy.

Remote Sensing Platforms

Categories of Platforms

  1. Ground-Based Platforms

  2. Airborne Platforms

  3. Spaceborne Platforms

Characteristics of Platforms

  • The platform type influences attributes like:

    • Distance from the object of interest

    • Frequency of image acquisition

    • Timing of acquisition

    • Coverage area

Ground-Based Platforms

  • Mobile Hydraulic Platforms: Elevation up to 15 meters.

  • Portable Masts: Less stable in windy conditions.

  • Towers: More rigid than masts for stability.

  • Weather Surveillance Radar: Detects atmospheric conditions such as typhoons.

Airborne Platforms

  • Balloon-Based: Operating altitude of 22 – 40 km.

  • Radiosonde Platforms: Measure atmospheric conditions (pressure, temperature, humidity).

  • Aircraft: Pros and cons include:

    • Advantages: High spatial resolution, flexible scheduling, easy maintenance.

    • Disadvantages: Requires permissions for airspace use, higher cost, limited coverage swath compared to satellites.

Spaceborne Platforms

  • Usage: Sensors are integrated into spacecraft, rockets, or satellites.

Remote Sensing Sensors

Types of Sensors

  • Passive Sensors: Collect data by detecting natural energy reflected from Earth (e.g., sunlight).

  • Active Sensors: Emit energy and measure the response reflected from the Earth (e.g., laser systems).

Specific Sensor Types

  • Microwave Radiometers

  • Magnetic Sensors

  • Gravimeters

  • Spectrometers

  • Cameras: Infrared, natural color, etc.

  • Radar: Real and synthetic aperture.

Characteristics of Images

  • Data Format: Images are stored in a rectangular grid of pixels.

  • Pixel: The smallest measurement unit of an image.

  • Digital Number Values (DN): Range from 0 (black) to 255 (white) in grayscale images.

  • Image Bands: Each band corresponds to a specific wavelength in the electromagnetic spectrum.

Sensor Characteristics

Spatial Resolution

  • Definition: Pixel size indicating the smallest feature detectable.

  • Influences: Number of pixels affects digital image quality.

    • High Spatial Resolution: More pixels, better detail.

    • Low Spatial Resolution: Fewer pixels, less detail.

Spectral Resolution

  • Definition: Wavelength intervals measured by the sensor.

  • Importance: Determines the sensor's ability to distinguish fine wavelength ranges.

Radiometric Resolution

  • Definition: Sensor's ability to record varying brightness levels.

  • Expressed in bits (e.g., 8-bit for 256 levels of brightness).

  • Higher bit depth allows discrimination of finer differences in energy.

Temporal Resolution

  • Definition: Time taken to revisit the same location for data collection.

  • Relevant to satellite orbit characteristics and sensor specifications.

  • High temporal resolution indicates frequent revisit capability.

Conclusion

  • Remote sensing is essential in many applications, including environmental monitoring and disaster management. Understanding sensors and platforms is crucial for utilizing remote sensing technologies effectively.

Acknowledgments

  • Thank you for attending the lecture.