Remote Sensing Quiz

Remote Sensing Course Outline

• GEOL 315 covers Introduction to Remote Sensing and GIS
• Topics include Introduction to remote sensing, Electromagnetic energy and remote sensing, Sensors and platforms, Aerial cameras, Multispectral scanners, RADAR, Remote sensing below the ground surface, Radiometric aspects, Geometric aspects, Image enhancement and visualization, Visual image interpretation, and Digital image classification.

Spatial Data Acquisition

• Georeferenced data is used by many disciplines, not just geology, for collection, analysis, and decision-making. Data represents information for a computer; information is data interpreted by humans.
• Spatial data, often spatio-temporal, is crucial for applications like geological mapping.

Ground-Based and Remote Sensing Methods

• Spatial data acquisition has two main types:
  • Ground-based methods utilize field observations, in-situ measurements, and land surveying in the real world.
  • Remote sensing methods use image data from sensors like aerial cameras, scanners, or radar to create a representation of the real world. Remote sensing analysis is performed on the acquired image data.

Remote Sensing Definitions

• Two definitions of remote sensing include:
  • The science of acquiring, processing, and interpreting images recording interactions between electromagnetic energy and matter.
  • The science and art of obtaining information about an object, area, or phenomenon via analysis of data taken by a device not in contact with the object.

Application of Remote Sensing

• Remote sensing generates image data related to the Earth's electromagnetic properties, which can be linked to real-world parameters or features.
• Combining remote sensing with ground data yields the best results.
• Remote sensing provides efficient area coverage compared to ground surveys, e.g., in aeromagnetic and ground magnetic surveys.
• Remote sensing initially provides surface information with limitations, requiring additional models for subsurface characteristics.

Remote Sensing Process and Topics

• Remote sensing involves a process with image data, observations, and spatial databases.
• Key topics include electromagnetic energy, sensors and platforms, radiometric aspects, geometric aspects, image enhancement and visualization, visual image interpretation, and digital image classification.

Electromagnetic Energy and Remote Sensing

• Remote sensing relies on measuring electromagnetic (EM) energy, primarily from the sun (visible light, heat, UV).
• Some sensors detect energy emitted by the Earth itself.
• The EM spectrum encompasses various wavelengths from gamma rays (most energetic) to radio waves (least energetic).

Waves and Photons

• EM energy can be described as both waves and photons (energy particles).
• EM waves are characterized by oscillating electric and magnetic fields perpendicular to each other and the direction of travel.
• Wavelength (distance between waves) and frequency (number of cycles per unit time) are inversely related.
• Energy of a photon is proportional to its frequency (and therefore inversely to wavelength).

Sources of EM Energy

• All matter above absolute zero emits EM energy due to molecular motion.
• The amount of emitted energy depends on temperature, emissivity, and wavelength. Higher temperatures relate to greater contribution from shorter wavelengths.

Electromagnetic Spectrum

• All matter emits EM waves across a broad spectrum (range of wavelengths) from gamma rays to radio waves.
• Remote sensing utilizes specific sections of the EM spectrum to generate relevant information about the Earth's surface.

Active and Passive Remote Sensing

• Passive remote sensing relies on natural energy sources, like sunlight, and measures reflected or emitted energy.
• Active remote sensing systems provide energy, e.g., radar and lasers, and measure the energy reflected back to the sensor.
• Passive methods operate during daylight hours, while active sensors work day and night.

Energy Interaction in the Atmosphere

• EM energy interacts with the atmosphere through absorption, transmission, and scattering.
• Gas molecules in the atmosphere absorb solar radiation particularly water vapor, ozone, and carbon dioxide.
• Absorption and scattering also affect energy transmission resulting in either reflected, transmitted, or absorbed energy at surface material.
• Atmospheric transmittance describes the proportion of energy that passes through the atmosphere at specific wavelengths.

Atmospheric Scattering

• Rayleigh scattering is caused by particles smaller than the wavelength of light.
• Rayleigh scattering is more effective with short wavelengths (like blue light), making the sky appear blue.
• Mie scattering occurs when the particle size is similar to or larger than the wavelength.
• Non-selective scattering occurs when particles substantially larger than the wavelength (e.g., water droplets in clouds) interact with radiation across the whole visible spectrum, resulting in white light.

Energy Interaction in the Earth's Surface

• Reflection, absorption, and transmission processes of EM energy by surface materials are important factors for interpreting remote sensing data.
• Specular reflection is from smooth surfaces, while diffuse reflection is from rough surfaces, scattering energy uniformly.
• Characteristics of visible reflected energy (spectral reflectance curves) reveal information about material compositions, e.g., vegetation, bare soil, and water.

Sensors and Platforms

• Sensors, often mounted to static or moving platforms (aircraft or satellites), measure EM energy reflected or emitted from the Earth's surface.
• Sensor types include gamma-ray spectrometers, multispectral scanners, thermal scanners, laser scanners, and radar altimeters.

Platforms - Airborne Remote Sensing

• Airborne platforms, such as aircraft, allow data collection from various heights and are suitable for acquiring information from specific areas.
• Key factors for aerial photography missions include scale, required percentage of overlap, flight line conditions, and temporal conditions to ensure data accuracy.

Platforms - Spaceborne Remote Sensing

• Satellites collect data from space and orbit, allowing imaging of entire regions, e.g. oceans to determine relevant details of a specific area.
• Key factors for satellite imagery missions include altitude, inclination angle, period, and repeat cycle.
• These factors affect the measurements and speed and quality of information extracted.

Image Data Characteristics

• Image data comprises various details that are essential for interpreting the data. These important components include image size, number of bands, quantization, spatial resolution, ground pixel size.

Visual Image Interpretation

• Visual interpretation is a key part of remote sensing data analysis, utilizing human observation.
• Key elements for interpreting images include tone, hue, texture, shape, size, pattern, and association.

Image Enhancement and Visualization

• Image enhancement methods improve the visualization of image data.
• Techniques such as histogram matching and atmospheric corrections can improve image contrast and detail.

Radiometric Aspects

• Radiometric aspects deal with image data corrections including cosmetic rectification (errors and noise) and atmospheric corrections (haze, sun angle, atmospheric effects).

Test your knowledge on remote sensing concepts, including reflection types, satellite orbits, and reflectance characteristics. This quiz covers key principles related to how radiation interacts with surfaces and the implications for satellite observations. Perfect for students studying Earth science or remote sensing.