Skip to main content

LiDaR Remote Sensing

LiDAR Remote Sensing: A Primer

LiDAR (Light Detection and Ranging) is a remote sensing technology that uses light in the form of a pulsed laser beam to measure ranges to the Earth's surface and various objects. This technology is incredibly versatile and has applications in a wide range of fields, including:

  • Cartography and mapping: Creating highly accurate 3D maps of the Earth's surface, including topography, vegetation, and buildings.
  • Forestry: Measuring forest height, density, and biomass.
  • Geology: Studying geological formations and identifying potential natural hazards.
  • Archaeology: Discovering and mapping ancient sites.
  • Environmental monitoring: Assessing changes in land cover, coastal erosion, and climate-related impacts.

Key Terminologies and Concepts

  1. Laser: A device that emits an intense beam of coherent light. LiDAR systems use lasers to emit pulses of light.
  2. Pulse: A short burst of laser energy.
  3. Time of Flight: The time it takes for a laser pulse to travel to a target and return to the sensor. This is used to calculate the distance to the target.
  4. Point Cloud: A collection of individual points, each representing a specific location on the Earth's surface. LiDAR data is often processed to create point clouds.
  5. Digital Surface Model (DSM): A 3D representation of the Earth's surface, including the tops of buildings, trees, and other objects.
  6. Digital Terrain Model (DTM): A 3D representation of the Earth's surface, excluding vegetation and other objects.
  7. Intensity: A measure of the strength of the laser return signal. This can be used to infer information about the properties of the target.
  8. Footprint: The area on the ground that is illuminated by a laser pulse.
  9. Accuracy: The degree to which LiDAR measurements agree with true values.
  10. Precision: The degree to which LiDAR measurements are consistent with each other.

Facts and Applications

  • High Accuracy: LiDAR can provide centimeter-level accuracy in measurements.
  • Versatility: LiDAR can be used to measure a wide range of objects, from small plants to large buildings.
  • Penetration: LiDAR can penetrate vegetation and other materials to measure underlying surfaces.
  • Real-Time Data: Some LiDAR systems can provide real-time data, allowing for immediate analysis and decision-making.


Comments

Post a Comment

Popular posts from this blog

Platforms in Remote Sensing

In remote sensing, a platform is the physical structure or vehicle that carries a sensor (camera, scanner, radar, etc.) to observe and collect information about the Earth's surface. Platforms are classified mainly by their altitude and mobility : Ground-Based Platforms Definition : Sensors mounted on the Earth's surface or very close to it. Examples : Tripods, towers, ground vehicles, handheld instruments. Applications : Calibration and validation of satellite data Detailed local studies (e.g., soil properties, vegetation health, air quality) Strength : High spatial detail but limited coverage. Airborne Platforms Definition : Sensors carried by aircraft, balloons, or drones (UAVs). Altitude : A few hundred meters to ~20 km. Examples : Airplanes with multispectral scanners UAVs with high-resolution cameras or LiDAR High-altitude balloons (stratospheric platforms) Applications : Local-to-regional mapping ...
Post a Comment
Read more

Types of Remote Sensing

Remote Sensing means collecting information about the Earth's surface without touching it , usually using satellites, aircraft, or drones . There are different types of remote sensing based on the energy source and the wavelength region used. 🛰️ 1. Active Remote Sensing 📘 Concept: In active remote sensing , the sensor sends out its own energy (like a signal or pulse) to the Earth's surface. The sensor then records the reflected or backscattered energy that comes back from the surface. ⚙️ Key Terminology: Transmitter: sends energy (like a radar pulse or laser beam). Receiver: detects the energy that bounces back. Backscatter: energy that is reflected back to the sensor. 📊 Examples of Active Sensors: RADAR (Radio Detection and Ranging): Uses microwave signals to detect surface roughness, soil moisture, or ocean waves. LiDAR (Light Detection and Ranging): Uses laser light (near-infrared) to measure elevation, vegetation...
Post a Comment
Read more

Optical Sensors in Remote Sensing

1. What Are Optical Sensors? Optical sensors are remote sensing instruments that detect solar radiation reflected or emitted from the Earth's surface in specific portions of the electromagnetic spectrum (EMS) . They mainly work in: Visible region (0.4–0.7 µm) Near-Infrared – NIR (0.7–1.3 µm) Shortwave Infrared – SWIR (1.3–3.0 µm) Thermal Infrared – TIR (8–14 µm) — emitted energy, not reflected Optical sensors capture spectral signatures of surface features. Each object reflects/absorbs energy differently, creating a unique spectral response pattern . a) Electromagnetic Spectrum (EMS) The continuous range of wavelengths. Optical sensing uses solar reflective bands and sometimes thermal bands . b) Spectral Signature The unique pattern of reflectance or absorbance of an object across wavelengths. Example: Vegetation reflects strongly in NIR Water absorbs strongly in NIR and SWIR (appears dark) c) Radiance and Reflectance Radi...
Post a Comment
Read more

Resolution of Sensors in Remote Sensing

Spatial Resolution 🗺️ Definition : The smallest size of an object on the ground that a sensor can detect. Measured as : The size of a pixel on the ground (in meters). Example : Landsat → 30 m (each pixel = 30 × 30 m on Earth). WorldView-3 → 0.31 m (very detailed, you can see cars). Fact : Higher spatial resolution = finer details, but smaller coverage. Spectral Resolution 🌈 Definition : The ability of a sensor to capture information in different parts (bands) of the electromagnetic spectrum . Measured as : The number and width of spectral bands. Types : Panchromatic (1 broad band, e.g., black & white image). Multispectral (several broad bands, e.g., Landsat with 7–13 bands). Hyperspectral (hundreds of very narrow bands, e.g., AVIRIS). Fact : Higher spectral resolution = better identification of materials (e.g., minerals, vegetation types). Radiometric Resolution 📊 Definition : The ability of a sensor to ...
Post a Comment
Read more

Radar Sensors in Remote Sensing

Radar sensors are active remote sensing instruments that use microwave radiation to detect and measure Earth's surface features. They transmit their own energy (radio waves) toward the Earth and record the backscattered signal that returns to the sensor. Since they do not depend on sunlight, radar systems can collect data: day or night through clouds, fog, smoke, and rain in all weather conditions This makes radar extremely useful for Earth observation. 1. Active Sensor A radar sensor produces and transmits its own microwaves. This is different from optical and thermal sensors, which depend on sunlight or emitted heat. 2. Microwave Region Radar operates in the microwave region of the electromagnetic spectrum , typically from 1 mm to 1 m wavelength. Common radar frequency bands: P-band (70 cm) L-band (23 cm) S-band (9 cm) C-band (5.6 cm) X-band (3 cm) Each band penetrates and interacts with surfaces differently: Lo...
Post a Comment
Read more