Remote Sensing System LiDAR

Researchers have identified a previously unknown Mayan city hidden within Mexico’s dense jungle using LiDAR (Light Detection and Ranging) technology.

• This technology enabled them to bypass thick vegetation and locate the ancient city.
  • It is now named Valeriana, in Mexico’s Campeche region.
    • The city features pyramids, plazas, a ballcourt, and a reservoir.

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What is remote sensing technology?

• • It is a process in which physical characteristics of an area are detected and monitored.
    • It is done through the measurement of reflected and emitted radiation at a distance typically from a satellite. 

• Special cameras capture remotely sensed images.

• • • It helps researchers in sensing things about the earth. 

What is LiDAR?

• LiDAR refers to Light Detection and Ranging. 
• It is a remote sensing technology that uses laser pulses to measure distances between a sensor and the Earth’s surface.
• By analyzing the reflected light, LiDAR creates detailed 3D maps of the terrain.
• Types of LiDAR 
  • Topographic:  It maps earth surface and captures land features above water. 
  • Bathymetric: This lidar measures underwater and maps the seafloor. 

How does LiDAR Work?

• Components: LiDAR technology includes a laser, scanner, and GPS receiver.
• Process:
  • Laser pulses hit surfaces such as vegetation, buildings, or land features.
  • The reflected light is recorded, and two-way travel time of each pulse is measured.
  • GPS and Inertial Measurement System (IMS) data are combined to determine distances and generate elevation maps.
• Point Cloud Data:
• • The collected data appears as a point cloud that records reflections from various surfaces.
  • Scientists analyze these reflections to identify different features (e.g., vegetation vs. buildings).
• Digital Elevation Model:
  • Data can be refined to produce a “bare earth” model, which removes trees and structures, showing only ground elevation.

LiDAR’s Importance in Archaeology

• Rapid Survey of Large Areas: LiDAR can quickly scan vast areas, uncovering hidden structures and features.

• Penetrating Dense Vegetation: It can see through dense vegetation, revealing archaeological sites that would otherwise be obscured.

• High-Resolution Mapping: LiDAR provides detailed 3D maps  which allow for precise analysis of ancient settlements.

• • • These maps are  valuable for geographers, conservationists, and engineers.

• Non-Invasive Exploration: It minimizes damage to archaeological sites, preserving them for future study.

• High Efficiency: Unlike traditional methods, which involve labor-intensive exploration, LiDAR allows scientists to analyze vast areas quickly from labs.

Challenges of LiDAR Systems

Despite its many benefits, LiDAR technology faces some challenges:

• Isolating the Signal: LiDAR systems need to distinguish the weak reflected signal from the much stronger outgoing laser beam. 

• This ensures the sensor accurately detects targets and avoids being overwhelmed by its own light.

• Atmospheric Interference: Dust, fog, and other airborne particles can create false readings by reflecting the laser beam before it reaches its intended target.  

• Power Limitations: Stronger laser beams provide more accurate data but require more power and are more expensive to operate.

• Safety Concerns: High-powered lasers can be dangerous to human eyes. 

• Device Crosstalk: Signals from nearby LiDAR devices can interfere with each other. 

• Cost and Maintenance: LiDAR systems can be expensive compared to other sensors.

• Unintended Object Returns: LiDAR might pick up reflections from unwanted objects like birds or flying debris. 

Applications of LiDAR Technology

• Atmospheric Sciences: Used to study atmospheric particles, wind patterns, clouds, and weather profiles.

• Astronomy: LiDAR helps measure distances to distant objects like the Moon with high precision and creates guide stars for telescopes.

• Automobile Industry: LiDAR is a key sensor in self-driving vehicles, working alongside cameras and radar to detect objects in the environment.

• Topographic and Bathymetric Mapping: Topographic LiDAR uses infrared to map land, while bathymetric LiDAR uses green light to map underwater features like riverbeds and seafloors.

• Agriculture: Helps map land topology, monitor crop growth, and assess needs for fertilizers and irrigation.

• Archaeology: Enables mapping of ancient structures under dense vegetation, such as old roadways and ruins.

• Environmental and Coastal Management: Supports flood modeling, shoreline mapping, emergency response, and vulnerability assessments for coastal areas.

• Consumer Electronics: Miniature LiDAR is now used in mobile phones, enhancing 3D scanning and augmented reality applications.

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