In recent years, UAV aerial surveying has developed rapidly with the advancement of UAV technology and digital camera technology. It is an important means of geographic information collection, characterized by low operating costs, high work efficiency, and high measurement accuracy, which greatly improves the accuracy and reliability of topographic mapping.
Unmanned aerial surveying (UAV) is a type of aerial photogrammetry, primarily used in low-altitude remote sensing. It is characterized by low cost, high speed and efficiency, flexibility, and wide applicability. The development of UAV aerial surveying benefits from the rapid advancements in UAV and digital camera technologies. Currently, it is mainly applied in topographic mapping, engineering construction, land resource surveys, geological disaster emergency response, and urban digitalization.
I. Characteristics of UAV Aerial Survey Technology
1. Low operating costs
Traditional manual surveying techniques primarily utilize satellite mapping. For the same survey area, the personnel and topographical costs required for traditional manual surveying are approximately 10 times that of UAV aerial surveying, and the project duration is about twice that of UAV aerial surveying. UAV aerial surveying equipment has a longer lifespan, lower maintenance costs, requires fewer personnel, and is more efficient, effectively reducing outdoor surveying time. From all aspects, UAV aerial surveying has significant advantages over manual surveying. Furthermore, due to the shorter operation cycle and lower surveying costs of UAV aerial surveying, it can enhance the overall market competitiveness of related enterprises, facilitate business expansion, and achieve better economic benefits.
2. Fast and efficient
When using drones for topographic mapping, staff can set the drone's flight path according to the actual conditions of the measurement area, optimize various settings, and rationally control the drone to quickly acquire geographic information data of the measurement area. Because drone aerial surveying is highly efficient, requires less on-site work time, and is more efficient and convenient in acquiring image data, it enables timely and effective analysis and control of geographic information data of the measurement area, quickly and efficiently completing topographic mapping tasks. This is especially true in large-scale topographic mapping operations, reducing the workload of surveying technicians and improving the efficiency of topographic mapping work.
3. High mobility
Traditional surveying operations require manual measurement of elevation points. In certain areas, such as rugged terrain, fast-flowing rivers, and wetlands, manual measurement is insufficient to meet the needs of surveying operations. Unmanned aerial vehicles (UAVs), on the other hand, offer advantages such as high mobility and rapid response. They are less demanding in terms of operating site conditions and surrounding weather, allowing for takeoff and deployment anytime, anywhere. Based on the received information, they can promptly conduct supplementary measurements. When site conditions are poor, UAVs can flexibly pause operations until conditions improve before resuming topographic surveying.
4. High accuracy of results
For areas difficult to reach by manual surveying, issues such as excessively large intervals between measuring points, common in conventional surveying operations, are major factors affecting the accuracy of topographic mapping. UAV aerial surveying can ignore most of these adverse environmental factors, accurately acquiring geographic information data for the surveyed area. Current UAV aerial surveying equipment is equipped with high-definition imaging devices, enabling rapid and clear acquisition of geographic information data for the surveyed area, providing high-precision raw data for topographic mapping. Furthermore, UAV aerial surveying possesses high coordination capabilities, combining satellite remote sensing and aerial surveying data to interact promptly with ground control systems, correcting erroneous images and data in a timely manner, ensuring the accuracy and quality of topographic surveying data.
II. Key Technologies for Unmanned Aerial Surveying in the Power Industry
(I) Image Acquisition Technology
In the traditional work model, outdoor operations are primarily conducted manually. Workers conduct on-site surveys of the power grid's installation location, then, considering local climate and geological conditions, obtain relevant parameters for power grid construction. However, power grid construction involves numerous tasks and requires a high degree of accuracy in the parameters.
First, during manual data collection, due to insufficient human technical skills, the relevant collection procedures were not strictly followed, leading to errors in data acquisition. Second, the quality of parameter acquisition is closely related to the accuracy of the equipment.
If the equipment is relatively outdated and its sensitivity is relatively poor, the acquired parameters will also contain certain errors. If there is a lack of accuracy in the parameter acquisition and calculation stages, then subsequent power grid planning and power grid laying location design will also lack a certain degree of rationality.
Therefore, power companies can use drones to acquire data parameters. Drones have long flight times, can cover relatively long distances, and are highly adaptable to different environments. For areas with complex terrain, staff can remotely control drones to acquire flight path parameters. Drones can also capture relevant images, providing staff with high-quality image data.
Drone aerial photography technology can effectively avoid errors in parameter acquisition caused by human factors. The parameters acquired by drones mainly include flight path curvature, altitude difference, and overlap. Staff can use these parameters to create video images, providing material support for subsequent flight path planning and ground control point deployment.
(II) Image Processing Technology
1. Image preprocessing techniques
Drones can accurately capture images of locked areas because they are equipped with positioning and multi-coordinate locking devices. However, during drone aerial photography, factors such as human installation and external wind forces can cause lens distortion, affecting the stability of the entire image and leading to image deformation. Therefore, to ensure image stability, operators need to adjust the drone's shooting angle in advance to maintain stability and prevent the drone from deviating from the pre-designed coordinate points during shooting.
First, staff need to plan the shooting route based on actual shooting requirements. Since drone shooting is primarily aerial, it requires connection to ground control points to ensure drone stability. Staff can monitor the overall shooting operation using the planned shooting route map and terrain map. Simultaneously, staff must remotely monitor the drone's flight status and record its flight parameters. If any abnormal parameters occur, the drone must be corrected promptly to prevent deviations in the shooting route or problems with the drone's camera lens.
Secondly, while the use of drone aerial surveying technology has alleviated some of the workload for staff, drone operation is relatively technically demanding. Therefore, staff need to improve their drone operation skills to ensure the quality of the images captured initially. After the drone aerial photography is completed, staff must check the images; if the images do not meet the requirements, they must be retaken.
2. Mapping Image Generation Technology
Digital line maps, digital elevation models, and digital orthophotos are essential components of surveying and mapping. Different image types require different data parameters and data acquisition methods. In the power industry, different imaging content can be selected based on the specific needs of the image creation. Digital line maps are key graphic representations of topographic features. Through digital line maps, workers can not only understand the elements contained in the terrain and the attributes of each element, but also clarify the spatial relationships between these attributes.
Digital line maps can be specific symbols on a map, or a point, line, or even a single surface. Digital line mapping is a commonly used surveying and imaging method. Digital elevation models (DEMs) are digital simulations of observed terrain based on elevation data. Unlike digital line maps, DEMs are physical terrain models, allowing workers to more intuitively understand terrain conditions and corresponding terrain data. Digital orthophotos have significant advantages in the power industry.
First, digital orthophotos are created by performing differential correction and mosaicking on digital data to form an orthophoto set. Based on the power grid construction needs of the industry, staff delineate the map area. Then, digital orthophoto technology is used to crop this map area, resulting in an image set. This image set combines the advantages of a map with the characteristics of an image. Through digital orthophotos, staff can not only visually view the terrain but also accurately obtain various parameters and corresponding geometric data within the map area.
III. Current shortcomings of UAV aerial surveying
The integration of UAV aerial surveying technology with geographic information technology has led to rapid development, with its advantages being self-evident. However, it also has certain shortcomings. For example, multi-rotor UAVs have a relatively small overall mass, and high-altitude winds can adversely affect UAV aerial surveying operations, causing unstable flight and reducing the clarity of the final image data. Furthermore, the development of UAV equipment sensors still has certain deficiencies, with insufficient accuracy, thus affecting the precision of aerial surveying data. Electronic communication technology is also a factor affecting the accuracy of UAV aerial surveying. To improve the accuracy and reliability of UAV aerial surveying data, it is essential to conduct aerial surveying work scientifically and systematically.
IV. Technical Applications of Unmanned Aerial Survey
Digital orthophotos
Digital orthophotos (DOM) are image data generated by correcting projection differences pixel by pixel in scanned digitized aerial photographs and remote sensing images using a digital elevation model, then mosaicking the images and cropping them according to the map sheet area. DOM can serve as background control information for map analysis, and can also extract historical or new information on natural resources and socio-economic development, providing a reliable basis for applications such as disaster prevention and public infrastructure planning. Furthermore, it can extract and derive new information to enable map revision and updates. As a reference for evaluating other data, it performs well in terms of accuracy, timeliness, and completeness.
Map surveying
Based on the required accuracy of the topographic map, adjust the scale, resolution, and overlap of the drone images. After producing the orthophoto map, use mapping software to first perform map interpretation (i.e., vectorization) in the office, then check its accuracy on the field, and conduct control surveying of the entire map to determine the coordinate system of the entire topographic map. Use mapping software to achieve functions such as map creation, map editing, and map analysis.
Digital line map
Digital line maps (DLGs) are a more convenient type of map for zooming, panning, querying, checking, measuring, and overlaying. Because digital line maps have small data volumes, they are easy to layer and can quickly generate thematic maps; they are also known as vector thematic information. This data can meet the requirements of various spatial analyses in geographic information systems, allowing for random data selection and display, and overlay with other products for easier analysis and decision-making.
Article source: Li Zhenhao (DDD), Chengdu Yuanshi Farstein, You got what you wanted.
