With a rapid shift to digital adoption, land surveyors are now replacing the use of rigid traditional surveying tools with drones. Although in an infancy stage, drones have taken a quantum leap with the increasing adoption across industries, including surveying.
Introduction to drone survey
A drone survey is a process of aerial survey using unmanned aerial systems (UAS), commonly known as drones. These are small, remote-controlled planes used for various purposes such as surveillance, mapping, photography, and videography. Often equipped with sensors or LiDAR payloads, drones provide advanced high-resolution images and sets of data that are analyzed and processed using software programs.
As drone survey creates a range of assets, it benefits various sectors of the economy with use in real estate and construction, agriculture, environmental monitoring, safety and security, surveillance, disaster management, law enforcement, etc. Moreover, with their low cost and ease of usability, drones as a surveying tool are becoming increasingly popular and are expected to grow exponentially over the next decade.
Figure 1: Drones used for agricultural purposes
Existing land survey techniques
There exist a number of survey techniques used for land surveying since ages. Some of the existing survey techniques include:
- Ground method, which includes:
- Total station (TS)
- Differential global positioning system (DGPS)
- Aerial photography
- High-Resolution Satellite Imagery (HRSI)
In addition to these, newer techniques such as LiDAR (Light Detection and Ranging) technology and Drone surveys are also adopted for surveys. At present, several surveys (especially on a larger scale) are conducted in a hybrid mode with two survey methods carried out simultaneously for more accuracy.
UAVs or drones can be used either by controlling remotely through wireless communication or they can be programmed to specific routes using navigation algorithms. They can have multiple configurations with payloads of sensors and digital imaging capabilities such as multispectral, high-resolution camera systems, and actuators. While drones were initially used primarily in the defense sector, they are now being explored as a surveying tool for their efficiency and time-saving factor, as well as for the advanced level data.
Figure 2: Aerial view captured by a drone
Use of drones for land survey
There are many uses of drones in land surveying. It measures distances between points on a map, creates 3D models of buildings and structures, and is commonly used for mapping purposes such that aerial photographs of a large area are taken and then stitched together to form a single image. Some of the uses of drones for surveying include:
Demarcation of land holdings
Land demarcation defines the boundaries of properties or land holdings. Thus, surveying of land using drones will demarcate the plot boundaries along with their shapes, sizes, and locations.
Surveying of land-use patterns
Drones survey will be useful to capture the types of land and its uses across the city. This will determine the existing land-use pattern and the area of each land-use, thus providing a useful exercise in the planning and development sector.
Measuring area of land
Drones capture high-resolution images which allows the surveyors to determine accurate measurements of the land accordingly. This can include areas of a smaller extent such as that of individual plots to a larger scale including vegetation cover, water bodies, forest land, etc.
Drones allow to capture expansive and detailed data, which helps determine the built-up of the area. Using various software, the aerial maps can also be overlayed with existing maps and projected buildings for detailed analysis and visualizations.
Drones survey amplify the management of land, including monitoring developments, construction activities, etc., by capturing aerial images and collecting data at regular intervals.
Capturing topographic data
Drones can capture several topographic data points, which provides accurate volume measurements. Besides, this data set will be useful to calculate and analyze topographic features. Capturing topographic data with drones is quicker, safer, and more accurate as compared to traditional manual surveying techniques.
Types of drone
As drone technology continues to grow, drones as a tool for surveying include several features. Some of these include aerial photography, video recording, and data collection. These are captured using downward-facing sensors, such as RGB or multispectral cameras, and LIDAR payloads.
There are two main types of drones used for surveying:
Fixed-wing aircraft: Typically powered by propellers or jet engines, fixed-wing drones are large aircraft that fly low over the ground. They are often used to survey large areas, such as farms and ranches. Fixed-wing aircraft can fly higher than rotary-wing aircraft, but they cannot hover.
Figure 3: Fixed-wing UAV
Rotary-wing aircraft: Smaller than fixed-wing drones, they don’t require a runway to take off and land. Instead, they hover above the ground, allowing them to capture detailed images of small areas. These planes can hover and maneuver quickly.
Figure 4: Rotary-wing UAV
Pros and cons of drones survey
Drone surveying is a relatively new technology that allows us to capture aerial images without using manned aircraft. To understand the application of drones for the survey, it is significant to explore their benefits as well as their challenges.
|Faster than traditional methods|
Surveying through drones is much faster, and requires less manpower as compared to traditional methods of surveying. With minimum human involvement, the cost of operating drones is much lower than traditional methods.
|Limited availability of drones|
Drones are not available in all areas, and thus limits the use of drones for surveys. Several countries, including India, are considering drones for survey and may therefore witness an increase in their availability.
|Better quality data than traditional methods|
With the use of sensors and multiple captured images, drones provide more accurate and exhaustive data as compared to the traditional methods of surveying.
|Limited availability of technically trained pilots|
Drones survey require hiring of technically skilled pilots to conduct a survey. The limited availability of trained pilots to conduct surveys makes it extremely expensive in addition to the cost involved in obtaining drones.
The traditional methods of manned aerial surveying emitted carbon dioxide, which is harmful to the environment. Drones on the other hand run on batteries and are therefore eco-friendly and sustainable.
|Lack of appropriate drone regulations|
Many countries to date do not have proper drone rules and regulations in place. This may pose a threat as people may not be aware of the protocols it needs to follow. Hence, introducing proper rules for people and companies, including that for surveys will help regulate drones usage.
|Map inaccessible areas|
Unlike that of traditional measuring methods which are restricted to unsafe slopes, terrain, or water bodies; drones can fly and map any area. This is useful to survey areas, including the former inaccessible areas easily.
Although drones have demonstrated the ability to work in environmental conditions with low air pressure, high altitude, and persistent cloud cover, however, they do not function well under severe conditions such as rainy or windy conditions.
Drone technology has grown exponentially over the past decade, with the use of drones expanding beyond military applications into commercial and recreational uses. They have proven very useful as a tool for survey because of their ability to map and survey areas that were either onerous or impractical in the traditional physical survey.
Despite significant advancements, there are still limitations to using drones for surveys. For example, drones are not available everywhere, and even if they were, there would be no qualified people who could fly them. They are, however, expected to become more widely prevalent in the near future. Drone technology as a method for surveying is advantageous especially to the government as it replaces the traditional labor-intensive and time-consuming process while generating a more detailed record with advanced-level data of surveyed land, properties and its components.
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