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.
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.
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 circuits, 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.
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.
| 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. |
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: –
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.
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.
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.
Two main types of drones can be distinguished:
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.
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.
Table: Comparison of pros and cons of Drone Types
| Multi-rotor Drones | ||
|---|---|---|
| Benefit | Maneuverability Compact design Increased payload capacity Ease of use | Increased flight range Stability in windy conditions Ability to recover from power loss |
| Drawback | Limited flight range | Take-off and landing area required More difficult to fly Less maneuverable Larger dimensions Increased cost |
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.
The main camera types used for agricultural applications are presented in the table below.
| Camera type | Main characteristics | Examples of Applications |
| RGB | Red, Green, Blue light High spatial detail Resembles visual observations | Crop monitoring Weed detection Plant cover |
| Multi-spectral (Satellite Remote Sensing and Landsat Satellite Series) | More spectral bands Information in near-infrared Higher costs | Plant 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 costs | Irrigation 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.
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.
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.
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.
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.
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