63 Unmanned Aerial Vehicle(UAV): Futuristic Technology of Remote Sensing

Introduction:-

Drones are revolutionizing remote sensing and GIS applications. For example, a Drone can be used by a farmer to collect photographs of complete fields to gather insights into the state of his crop. The significant advantage of the UAV machines is that this can be done more quickly, easily, and cheaply compared to conventional surveys done on foot, by GPS (Global Position System: Different Segments of GPS, its working Principle, Popular Substitute of GPS), etc. Spatial information from drone images can help better decisions on where and when to improve the required target surface. In aviation terminology, it is known as RPAS (remotely piloted aerial system).

Agriculture, as you may be aware, is undergoing significant problems. The global population is forecast to reach 9.7 billion by 2050. Agriculture output must expand to feed all of these people. At the same time, agriculture’s environmental effect must be decreased. This requires the appropriate use of soil and water resources and the maintenance of forest cover and biodiversity. Drones are seen as one of the solutions to support next-generation agriculture.

Main Components of a Drone

Drone(UAV)
Figure: Main components of a drone system: Drone, remote control, ground control station (tablet), and drone battery.

Drone Platform, Remote Control, and Ground Control Station

A drone system’s main components are the drone platform, GPS, and remote control. A ground control station is frequently added. This is a computer, laptop, or tablet that displays drone status information, a map of the flying region, and real-time photographs captured during the flight.

Batteries

The main type of battery used for drones(UAVs) is Lithium Polymer. This type of rechargeable battery can provide the required high electrical discharge to power the motors and weighs relatively little.

However, this type of battery requires attention: overcharging, overheating, short circuit, and physical damage may result in catastrophic failure, including expanding or breaking packaging, electrolyte leaking, and fire. Therefore safe charging, storage, and transport procedures are really important.

Drone Battery
Figure: Different types of LiPo batteries used for drone flights

Global Positioning System (GPS)

Most drone systems have included global positioning system (GPS) components. GPS, also known as GNSS (Global Navigation Satellite System), allows the user to locate the drone (Global Position System: Different Segments of GPS, its working Principle, Popular Substitute of GPS). While the drone is flying, the GPS data is utilized to construct a flight record, which stores the flight coordinates. Furthermore, this position data is utilized to follow the drone in real-time on the map shown on the ground control station.

GPS
Note: –  what is Ortho-mosaic imagery In simple words we may say about ortho-mosaic imagery that it is a set of images that have been stitched together like taking a landscape picture with an accurate 2D representation of a ground.

How to Apply Remote Sensing With Drones

As we discuss different forms of remote sensing (The Basic Concept of Remote Sensing, What is Hyperspectral Remote Sensing and its important Applications) in our previous article, we have a basic knowledge of the working principle of remote sensing. Here in this part of the article, we will learn the different types of resolution which may be used while planning a drone flying plan. Following are the major types of resolution used in remote sensing systems as well as in UAVs: –

  1. Spatial resolution:

First, important resolution refers to the size of one pixel on the ground of the image acquired with a drone. The following figure highlights the different spatial resolution imagery of the ground for a better understanding of it. In simple words we may say, where the size of a pixel is small, you can identify more details in an image. The image presented on the right has a high spatial resolution as compared with the image illustrated on the right.

Spatial resolution
  1. Spectral Resolution: –

It discriminates between different ranges of EMR (electromagnetic radiation) (The Concept of Microwave Remote Sensing, its Geometry, and its Applications) and describes how many spectral bands are measured by a camera and at which wavelength these bands are located. The RGB camera is a well-known example. This camera measures three spectral bands in the visible EMS spectrum range, as illustrated in the image below: red, green, and blue. A multi-spectral camera measures in multiple bands and covers near-infrared wavelength bands.

Spectral resolution
  1. Temporal Resolution: –

It denotes how frequently a picture of the same region or field is collected. Changes throughout time can be noticed in greater detail when photos are taken more often. Drought affects an agricultural area, for example, with plants drying out after a period of no rainfall.

.Types of Drones in Remote Sensing Application

Two main types of drones can be distinguished:

  1. Multi-rotor Drones: –

Multi-rotor-based drones look more like a helicopter but have multiple rotors. Control of drone movement, in this case, is achieved by varying the relative speed of each rotor. Multi-rotor drones are constructed with varying numbers of rotors. Common types are tricopter, quadcopter, hexacopter, and octocopter referring to systems with 3, 4, 6, and 8 rotors.

  1. Fixed-wing Drones:-

Fixed-wing drones look like airplanes and can be identified by their rigid wing. Because of this rigid wing, they cannot do vertical lifts. Instead, they glide to higher altitudes.

Drone type(UAV)1
Drone typeUAV2

Table: Comparison of pros and cons of Drone Types

Multi-rotor Drones
Fixed-wing Drones
BenefitManeuverability
Compact design
Increased payload capacity
Ease of use
Increased flight range
Stability in windy conditions
Ability to recover from power loss
DrawbackLimited flight rangeTake-off and landing area required
More difficult to fly
Less maneuverable
Larger dimensions
Increased cost

Sensors and Cameras for Drones

In the slipstream of drone technology development, the availability of drone-specific cameras and sensors is changing rapidly. Cameras are becoming smaller and lighter to fit the drone. But applications in agriculture also stimulate the large-scale production of specific cameras to identify, for example, the stress in crops. Here we provide a short overview of different camera types and their potential application.

Drone Cameras

The main camera types used for agricultural applications are presented in the table below.

Camera typeMain characteristicsExamples of Applications
RGBRed, Green, Blue light High spatial detail Resembles visual observationsCrop monitoring Weed detection Plant cover
Multi-spectral
(Satellite Remote Sensing and Landsat Satellite Series)
More spectral bands Information in near-infrared Higher costsPlant health Biomass and yield mapping Nutrient deficiencies Better discrimination between features Helpful for more remote sensing operations (spectral indices, PCA, etc)
Thermal
(Remote Sensing Using the Thermal Infrared Spectrum Range)
Measures temperature differences More complex measurement Higher costsIrrigation and water management Soil water status Disease mapping

Furthermore, the potential for specialized drone cameras is being examined. For example, hyperspectral (What is Hyperspectral Remote Sensing and its important Applications) cameras capture pictures with extremely fine spectrum information that can be used to recognize the disease. Another kind of camera, known as LiDAR (LIDAR Remote Sensing: Historic Development, components, and Advantage of LIDAR Remote Sensing), measures 3D information in great detail by using light waves from a laser. This might be used to determine the amount of any object to be collected by measuring the 3D structure of objects in the targeted area.

Sensors

In addition to cameras, sensors (UAV) are also available for point measurements of particles in the air or water. These chemical sensors measure concentrations of a selection of substances for which they are sensitive. The sensors are positioned under the drone and by flying around samples are taken at regular intervals. From this concentration, maps can be derived. Possible applications are measuring ethylene as an indicator of fruit’s ripeness or determining irrigation basins’ water quality.

Drone Sensor
Figure: Examples of chemical sensors under a Drone.

Application of UAV-based Remote Sensing

Until five years ago, satellite images were the main tool for observing crop growth in agricultural fields. Several satellite systems, such as Sentinel-2, or Landsat, are regularly used and crop-specific monitoring applications have been developed. An important advantage of satellites is that they can cover the complete globe regularly.

Application of UAV Based Remote Sensing
Application of UAV Based Remote Sensing2

The increasing availability of drones provides a flexible alternative. As a drone user, you can decide on your timing for data acquisition. But also you can select different cameras and sensors to attach to the drone depending on the information needed for the application you are targeting.

  1. Real-time monitoring
  2. Fire monitoring
  3. Crop growth monitoring
  4. Helpful for precision farming
  5. Yield estimation
  6. Disaster management task
  7. High-detail 3D terrain modeling
  8. Urban planning
  9. Transport planning

Rules and regulation for Flying a Drone in the Field

Nowadays we see that the number of drones is increasing very rapidly. The drone is used by commercial companies, research institutes,s and a lot more, so it is very important to set some rules and regulations for drone(UAV) flying due to safety reasons. Four major regulations can be remembered by a drone pilot while flying a drone in the air.

  1. What is the flying height of the UAV in the targeted area
  2. Take care that you can see your drone while flying. This height is known as the Visual Line of Sight.
  3. Don’t fly any drone over a group of people.
  4. Don’t fly it near the airport with permission. It will create a severe problem.
  5. Carefully check the laws of your country for UAV use.

Major Components of UAV Flight Planning

  1. The first and most important step of UAV flight planning is to prepare a flight plan
  2. check the available digital or analog map of the target area,
  3. make sure early the potentially hazardous objects like hills, tall buildings, etc. which can cause damage to the drone,
  4. Check the weather forecast before the flight,
  5. check the battery status,  
  6. Calculate how much time is required for completing the flight,
  7. evaluate how side and end lap are required for the field,
  8. What type of drone is required for the target region etc?

Before take-off

  1. Check the actual situation in the field
  2. Decide on take-off and landing area,
  3. Emergency landing area

During flight

  1. Check the drone and camera system, and data on the ground station during the flight.
  2. Check the situation on the ground and in the air.

Recommended Books for the Detail Study of Unmanned Aerial Vehicle(UAV)

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