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Unmanned Aerial Vehicles


Unmanned Aerial Vehicles (UAVs)—commonly called drones—are pilotless aircraft used as remote sensing platforms to acquire very high-resolution geospatial data. They fly at low altitudes (typically 50–300 m), enabling them to record centimeter-level details of the Earth's surface.

UAVs are increasingly used in remote sensing because they offer on-demand data acquisition, flexible sensor deployment, and the ability to fly under cloud cover, making them ideal for scientific, environmental, and disaster applications.

Characteristics

✔ 1. High-Resolution Data Acquisition

  • UAVs can collect imagery with spatial resolutions up to <1 cm.

  • Suitable for detailed mapping of vegetation, buildings, hazards, and micro-topography.

✔ 2. On-Demand and Rapid Deployment

  • Can be launched quickly anytime data is needed.

  • Extremely useful after floods, landslides, earthquakes, or in inaccessible terrain.

✔ 3. Operational Flexibility

  • Able to fly:

    • in rugged terrain

    • over small areas

    • in hazardous environments where humans cannot reach

  • They operate below cloud cover, unlike satellites affected by weather.

✔ 4. Versatile Sensor Payload

UAVs can carry different types of sensors depending on the application:

Primary (Navigation) Sensors

Built into the UAV for stability and control:

  • GPS/GNSS

  • IMU (Inertial Measurement Unit)

  • Accelerometers

  • Gyroscopes

  • Magnetometers

  • Barometers / Altimeters

These ensure accurate positioning and flight control.

Secondary (Remote Sensing) Sensors

Mounted externally for data collection:

  • RGB cameras (photogrammetry)

  • Multispectral cameras

  • Hyperspectral sensors

  • LiDAR (3-D terrain mapping)

  • Thermal infrared cameras

  • Radar (on larger UAVs)

  • Gas sensors (air quality)

  • SONAR (water depth in special systems)

✔ 5. Cost-Effectiveness

  • UAV surveys are cheaper compared to manned aircraft and high-resolution commercial satellites.

  • Require fewer human resources and provide repeatable measurements.

✔ 6. Precise Geospatial Accuracy

  • Equipped with RTK/PPK GNSS, UAVs can achieve centimeter-level positioning accuracy.

  • Ideal for DEM/DSM generation and engineering surveys.

Types

UAVs are usually classified based on flight mechanics, payload capacity, and mission requirements.

1. Fixed-Wing UAVs

✔ Description

  • Look like mini-airplanes.

  • Use wings for lift, making them energy-efficient.

✔ Features

  • Long endurance (1–3 hours)

  • High flight speed

  • Can cover large areas

  • Can carry larger payloads

  • Need a runway or catapult for takeoff/landing

  • Cannot hover

✔ Applications

  • Large-scale mapping

  • Agriculture

  • Coastal and forest surveys

  • Pipeline/road corridor mapping

  • Disaster assessment over large regions

2. Rotary-Wing UAVs (Multirotors)

Includes quadcopters, hexacopters, and octocopters.

✔ Description

  • Use multiple rotors to generate lift.

  • Most common UAV type for remote sensing.

✔ Features

  • Vertical Take-Off and Landing (VTOL)

  • Can hover continuously

  • Highly maneuverable in confined or rugged spaces

  • Shorter flight time (20–45 minutes)

  • Lower energy efficiency

  • Limited coverage area per mission

✔ Applications

  • Precision agriculture

  • Urban mapping

  • Building inspections

  • Landslide surveys

  • Archaeology

  • Environmental monitoring in limited areas

3. Hybrid UAVs

Combine features of fixed-wing + rotary-wing systems.

✔ Description

  • Have wings for forward flight and rotors for vertical lift.

  • Can take off vertically, then switch to efficient fixed-wing mode.

✔ Features

  • VTOL capability + long endurance

  • No runway needed

  • Better range than multirotors

  • Ideal for medium to large areas

✔ Applications

  • Corridor mapping

  • Long-distance mapping missions

  • Search and rescue

  • Coastal and wetland monitoring


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