The unmanned aerial vehicle (UAV) aerial surveying system has been widely used in various industries due to its advantages such as flexibility, convenience, high efficiency, speed, and low cost. The following will detail the main steps and specific details of UAV aerial surveying.

Main Process Overview

The fieldwork of UAV aerial surveying mainly consists of four stages: flight preparation, flight operation, export of aerial survey data, and deployment of control points. Among them, the flight preparation stage is crucial for ensuring the smooth progress of the entire aerial survey process. It involves various preparatory tasks before the flight, collecting necessary data, selecting takeoff and landing points, and planning flight routes.

Detailed Steps

1. Flight Preparation Stage

The pre-flight preparation work is crucial as it directly affects whether the UAV can operate normally and the quality of the operation. This step mainly includes assembling the UAV, testing the avionics system, and inspecting UAV accessories. The purpose of these tasks is to ensure that the UAV can operate smoothly during the mission and to avoid any interruptions due to equipment failures, thereby affecting the progress of the operation.

To ensure that UAV aerial survey operations can be conducted during the optimal time frame, it's necessary to charge all electrical devices in advance. This includes the power batteries for the UAV, radio transmitters, remote controllers, and camera batteries. After charging is complete, it's important to check whether all batteries are fully charged and to verify once again that all equipment accessories are complete and stored properly.

In terms of data preparation, it's essential to gather various relevant data and collect basic information about the aerial survey area, such as topographic maps and satellite images. These data can help us better understand the terrain and landforms of the survey area, providing strong support for subsequent flight route planning and flight operations. Additionally, it's important to confirm whether there are any areas within the survey area that require special reporting, such as military camps or airports, to ensure the legality of the flight operation.

The selection of takeoff and landing points is also an important task during the flight preparation stage. When choosing these points, factors such as the UAV model, takeoff and landing conditions, and surrounding environment need to be considered. Initially, preliminary screening can be done indoors using online mapping resources. Then, a site reconnaissance should be conducted before the flight to confirm whether the selected alternate points meet the requirements for takeoff and landing conditions, ultimately choosing suitable points. To improve efficiency and safety, takeoff and landing points should preferably be selected in open grasslands or unused areas.

Flight planning is a crucial step to ensure that UAV aerial survey operations are conducted efficiently and accurately. After determining the boundaries of the survey area, it's necessary to divide the entire area into sections, considering the selected takeoff and landing points. The purpose of this division is to ensure seamless integration between each flight block, avoiding instances of missed or duplicated flights. Upon arrival at the site, adjustments and optimizations can be made to the pre-defined sections based on actual conditions, aiming to improve work efficiency and flight safety. In situations with low wind speeds, adjustments to the wind direction settings can also be made to shorten the UAV's flight time.

2. Flight Operation Stage

When the UAV reaches the takeoff and landing point, it's essential to observe the surrounding environment, particularly for any tall obstacles such as buildings or power towers in the takeoff and landing direction. To avoid collisions, it's advisable to choose a left or right circling direction to bypass these obstacles. In cases of strong winds, consideration of wind direction is crucial to ensure operations against the wind during takeoff and landing while choosing crosswind during flight. When setting up the takeoff and landing points, the circling direction must be determined based on the terrain in the landing direction. During catapult takeoff, the operation should be swift and forceful to prevent the catapult from jamming. In case of a jam, immediately insert the safety pin and reset the launch frame after releasing the force.

Once the aircraft is airborne, real-time tracking of flight parameters such as battery level, flight duration, and altitude is conducted through the ground control station. In urban or densely populated areas where the takeoff and landing points are far from the survey area, it's important to set an appropriate radio disconnect time before takeoff. Based on the flight duration, convenient traffic and open terrain within the survey area should be selected as waiting points to ensure timely reconnection of the radio link with the aircraft and prevent the aircraft from automatically returning due to prolonged radio disconnection. Signals are prone to interruption during aircraft turns, so when selecting waiting points, it's advisable to choose the middle section of the flight path for better signal stability.

During landing, the UAV can choose between circling or straight-line landing. Given that circling landing requires higher terrain conditions, straight-line landing is usually recommended. The ideal area for straight-line landing is within a range of 15 meters to the left and right of the designated landing point and 25 meters ahead and behind it, along the landing direction. In practice, landing is typically initiated 25 to 30 meters in advance, especially in poor terrain conditions, and careful attention must be paid to setting the landing point. If the aircraft delays landing and there are obstacles behind the landing point, a net interception can be chosen based on the site conditions. If there is significant delay and the battery level is still sufficient, consider canceling the landing and let the aircraft return to hover near the original landing point, reset the landing point, and then land.

3. Aerial Survey Data Export

After the aircraft lands, it's important to promptly copy the flight data and photos, check the quality of the photos, and confirm their accuracy before proceeding with the next flight. When there are multiple flight missions, pay attention to the naming conventions of the photos to avoid duplication. After exporting the data, promptly record relevant information about this flight, such as block numbers, flight duration, number of photos, etc., to facilitate subsequent work.

4. Control Point Deployment

The deployment of control points, like ground control points, should cover the entire survey area and be evenly distributed. For UAVs equipped with network RTK and PPK capabilities, the number of ground control points can be reduced by 50% to 80% depending on the actual situation. When deploying control points, it's important to follow principles such as clear marking, unobstructed visibility, even distribution, coverage of the survey area, fixed positions for control points, and deployment on a flat surface with no height differences. Additionally, ensure that the UAV can capture clear images of the control points during fieldwork and that the control points can be easily and accurately identified during post-processing.

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