Research on GNSS technology of UAV remote sensing measurement

1.Overview of GNSS technology development

The traditional measurement methods are mostly carried out in the mode of manual+equipment+technology, so the measurement efficiency and accuracy cannot be properly guaranteed. The existing GNSS technology combines various technical advantages, integrates the operation of UAV equipment, obtains real-time and real aerial photography data, and can deliver high-quality data, providing a first-rate work base map for remote sensing measurement. It can be said that under the revolution of technological innovation, it will provide more convenient places for the remote sensing measurement industry at this stage, with less investment and simple operation mode, which can greatly improve the application scope of GNSS technology and help the UAV positioning and measurement work to achieve the set goals efficiently. GNSS technology can cooperate with the aerial triangulation mode, scientifically reduce the field image control points, and then complete the survey of more areas within the given time, reduce the cost of a single operation, provide the survey industry with higher necessity of application, promote the technology to be more widely promoted, shorten the industrial operation cycle, and provide basic support for the stable operation of society.

2.GNSS technology application characteristics

Application advantages

First, high accuracy. The equipment used in GNSS technology is equipped with a remote sensing measurement system under the innovative application form, which can complete the high-precision acquisition and transmission process with a lower overall power consumption during continuous operation. When the UAV conducts remote sensing measurement, it can reduce the flight load by means of lightweight design, and add a storage module in multiple media inside the equipment to ensure stable data transmission. The most important part for accuracy assurance is the design application of the UAV camera's application performance. The camera used in GNSS technology can achieve the time accuracy control process under the real-time ns level. Therefore, the camera's exposure data can be better protected during the exposure signal, and all kinds of collected geographic information attributes can be transmitted in real time to enhance the information accuracy.

Second, the scope is wide. GNSS technology not only has a wide range of operations, but also has high application efficiency within its scope, which is related to the overall performance of UAV equipment and aerial cameras. For example, the voltage input stage of the receiver equipment can support the wide voltage factor, so when the UAV carries various equipment, it can better control the power supply voltage problem, which is beneficial to the improvement of flight duration. In addition, the OEM board equipment used by GNSS technology can effectively track multi-frequency satellite signals and accurately obtain the collected geographic information, which increases the range of observation data and helps the subsequent processing software process to obtain more high-quality raw data, thus improving the application effectiveness of GNSS technology in large-scale operations

Third, it can be used in harsh environment. GNSS technology provides an accurate solution to the difference between dynamic and static modes with the help of the KGO difference algorithm, and can provide good calculation support for single point positioning. Therefore, GNSS technology can complete high efficiency remote sensing measurement regardless of whether the external measurement environment is good or not. Data shows that this technology can reduce the number of ground image control points to less than 20% of the original demand, so most harsh environments will not have a significant adverse impact on the application of GNSS technology. With the gradual operation of the process of acquisition, reception and calculation, the technology can better complete the innovation and transformation of the technology integration mode, and achieve the work adaptation to the harsh environmental conditions such as strong interference, multiple obstacles and strong concealment while improving the measurement efficiency.

3．technology application types

3.1 Disaster emergency

The southern region of China was hit by floods in 2020. During this period, GNSS technology was used to provide high-definition image support for the government rescue department to help the disaster areas better resist adverse effects. In fact, the number of disasters that occur every year in China is not small. In serious cases, it will affect the development of transportation and economy, and disaster emergency measures need to be carried out under more severe conditions. Therefore, high-precision and real-time image data can play a good role in emergency aid. With the help of GNSS technology, flight acquisition operations in various disaster areas can be carried out, and various geographical data can be collected in time through the equipment differential positioning system, and the high-definition data can be integrated by the quick spell software to help the rescue command work obtain the first-hand scene situation, promote the more scientific and effective implementation of emergency decision-making, and ensure social stability.

3.2Power maintenance

Relevant troubleshooting and maintenance of power line network is a necessary work for the transmission industry. However, with the improvement of transmission level, the inspection of power line network gradually shows the undesirable phenomenon of low efficiency. In order to maintain the operation under high efficiency, the access of information technology for power maintenance is an urgent matter. The use of UAV equipment for patrol inspection and maintenance of power lines is characterized by fast and clear application. The UAV operation mode can also improve the efficiency of the original maintenance work and help the power industry to complete the patrol inspection more efficiently and safely. For example, using a digital product of a certain brand as a remote sensing measuring equipment can accurately locate the location of the fault line in the process of troubleshooting a long line, help the line patrol personnel get timely feedback information, and increase the effectiveness of power maintenance.

3.3Survey route

China's road construction industry has a relatively high development advantage, and the mileage and speed of high-speed railway construction have reached the world-class level. However, during the construction of road and bridge projects, the survey process of the line has great difficulties for the survey personnel. For example, the railway line has a very long crossing distance, and will form a mountain tunnel, overhead road and bridge and other line operation types under different terrain conditions. It is not more accurate to borrow only the traditional survey method The existing route data can be obtained quickly, so the UAV aerial survey mode is the most important application form of the survey route at this stage. Using the method of no control point in the UAV image acquisition can better collect the ground route information, so that it can be mapped and used for the transportation industry erection and route planning. This technology can meet the accuracy requirements for route survey.

3.4case analysis

At present, major domestic companies have launched airborne GNSS-assisted UAV aerial triangulation system to meet the defect of insufficient accuracy of POS-assisted aerial triangulation and greatly reduce the number of image control points. For example, an airborne remote sensing GNSS equipment uses a high-precision GNSS OEM motherboard, with a data sampling rate of up to 20Hz, supports multiple parallel receiving channels, and can track GNSS satellite signals to the maximum extent. At a survey site, the surveyors measure the total area of about 50km by using unmanned aerial vehicles ²、 In hilly areas, UAV equipment has flown 13 routes in 2 hours and taken a total of 897 photos, which can preliminarily meet the measurement requirements. With the help of the ultra-high precision image mapping system without control points (P8 receiver+KGO post-processing software) carried by the UAV equipment, the local survey work was well completed. According to the data, the average flight height reached 600 meters, and the original image data obtained was relatively rich. After KG0 difference calculation, the fixed rate reached 98.07%, and the data quality achieved was good.

The sophisticated helix antenna design allows GNSS helix antennas to be widely used in UAVs. In this way, UAV aerial survey has the characteristics of flexibility, high efficiency, low operation cost, wide application range and short production cycle. In recent years, the UAV industry has developed rapidly. Sophisticated helix antenna has been widely used in surveying and mapping, precision agriculture, disaster monitoring, traffic patrolling , security monitoring and other fields. Especially in field work, it reduces the workload of operators and speeds up the operation efficiency.