D2000 is Equipped with D-OP4000 Tilt Camera Module to Help the Smart City Construction in Downtown Shanghai

With the continuous transformation and upgrading of my country's "digital city" to "smart city", GIS applications based on two-dimensional vector data have been difficult to meet the needs of urban intelligent management. The important construction task of national basic surveying and mapping during the "14th Five-Year Plan" period, the urban 3D platform can provide the city's 3D base for the comprehensive management of natural resources and smart city management, and provide basic data and information for urban planning, management, fire protection, emergency response, ecological environment monitoring, etc. management platform. Therefore, how to quickly and accurately obtain 3D data in geographic space has become an important support for the 3D construction of real China. UAV oblique photogrammetry has become an important way to obtain oblique photography data due to its efficient and flexible data acquisition capabilities.

However, compared with professional aerial cameras, it has a lighter load and a shorter focal length of the camera. How to obtain high-resolution UAV oblique photography images in the central urban area with many high-rise buildings and large building height differences has become a technical difficulty in urban UAV oblique photogrammetry. This study uses the Pegasus D2000 quadrotor UAV, equipped with a telephoto D-OP4000 (focal length: 40mm for downward view, 56mm for side view) oblique photography module, to explore the data acquisition and real-scene 3D of UAV oblique photogrammetry in the central urban area of a megacity Model application.

Range of study area

The research area is located on the north bank of the Huangpu River in Shanghai, adjacent to Nanjing Road. It is the famous Museum of International Architecture in Shanghai. The rest of the buildings higher than 100 meters are relatively small, so it is necessary to obtain high-resolution UAV oblique photography images, which is very difficult.

Photos of high-rise buildings in the study area

The technical route is shown in Figure 3. According to the DSM data of building heights in the North Bund area of Shanghai, the PHOTOMOD digital elevation model is used to manually edit the DSM. Height-changing flights are carried out for some buildings with a height of 320 meters and 260 meters.

Artificial Terrain

The digital surface model of the research area is shown in Figure 4. The building heights range from 3 to 320 meters, and the tallest building, the Magnolia Building, is 320 meters high. Use the PHOTOMOD DEM editing module to manually edit, and manually modify the DSM model to center on the Magnolia Building (extend 100 meters) with heights of 80 meters (red), 50 meters (light yellow), 30 meters (yellow) and 10 meters (green) ) of the stepped terrain.

Route Planning

According to the artificially simulated terrain, the altitude flight is carried out, the route planning flight altitude is 319 meters, and the highest flight altitude of Magnolia Plaza is 400 meters. Course overlap 80%, side overlap 70%.

Image control point layout and measurement

Since the survey area is located in the central urban area, this project arranges ground control points and inspection points according to the distance of 200-300 meters, and adopts the existing zebra crossings, step corners, etc., as the image control points, and uses the CORS network mobile station mode The RTK measurement method measures the coordinates of the image control points, and a total of 50 image control points and inspection points are arranged. 

Ground control point measurement and distribution map

Drone Flight

Since the survey area is located in the downtown area of Shanghai, the electromagnetic interference is relatively serious. In order to maintain the communication between the drone and the ground station, the helicopter docking station on the roof of the 260-meter-high Raffles Building was chosen as the take-off point. Taking off from the roof has two advantages: (1) The effective communication distance between the ground UAV and the ground station in the city center is about 1km, but at the top of the Raffles City tower, the communication link of the aircraft can be guaranteed to be normal, which is convenient for handling special situations and guarantees flight Safety; (2) Since the load of D-OP4000 is heavier than that of orthophoto and D-OP3000, flying on the roof of a 260-meter-high building can minimize the power consumption of the UAV during the climbing phase and improve the performance of UAV tilt photography. Airline flight time. The area of the survey area is about 5.46 square kilometers, and a total of 4 sorties were flown. The photos of the field operations are shown.

UAV flight operations

View of the North Bund skyline in Shanghai

The side views of the North Bund were obtained sequentially along the centerline of the Huangpu River waterway, and then all the side views were spliced into a landscape map of the Bund skyline in Shanghai, as shown in Figure 9. Through the production of the skyline landscape map, the beautiful landscape of the Wanguo Architecture Museum on the north bank of the Huangpu River in Shanghai is well displayed. It provides excellent materials for urban construction planning and historical building protection and display in Shanghai.

Restoration and preservation of historic buildings

The Bund is known as the Museum of International Architecture in Shanghai, so how to protect and repair it is an important proposition in Shanghai’s urban construction. Take the Shanghai Building (formerly known as Broadway Mansions Broadway Building) designed by the famous British designer Francais in 1934 as an example. For example, through UAV aerial photogrammetry, we can accurately obtain the facade and design dimensions of the Shanghai Building, and provide visible repair effects and protection construction planning for the protection and repair plan of the Shanghai Building based on the real-world 3D model

This research is located in the center of Shanghai, where there are many high-rise buildings and the electromagnetic environment is complex. It is very representative in the application of smart cities and oblique photogrammetry across the country. This research creatively adopts the high-flying scheme of artificial simulation of terrain change, combined with the performance characteristics of D-OP4000 telephoto (40mm) full-frame, it solves the problem of multiple flights in the central urban area, which not only improves the oblique aerial photogrammetry Efficiency, but also to ensure the quality of data collection. The main conclusions are as follows:

(1) Artificially simulated terrain-changing flight: The height of urban buildings is artificially optimized and simulated into terrain, and then combined with the planning and design of the UAV housekeeper's altitude-changing route, it solves the problem of inconsistent flight resolution of UAV city modeling and one The survey area needs to fly multiple times according to different floor heights. It not only improves the efficiency of data collection, but also ensures the quality of data;

(2) Telephoto take-off from the roof: Due to the high floors in the central urban area, it is difficult to collect high-resolution images with ordinary focal length cameras. For example, the tallest building in this research area is 320 meters. High-rate images, the flight altitude is about 191 meters, and flying dangers are prone to occur near tall buildings with building heights of 260 meters and 320 meters, and in the flight plan, different heights should be adopted according to different building heights. This is what we usually say There are many cases. But in this study, the camera with a long focal length (40mm) can be used to collect data with the same resolution (3cm) at a higher flying height (319m). At the same time, the take-off point is set on the roof of a 260-meter-high building, which not only solves the problem of strong electromagnetic interference of UAV flight in the city, but also improves the efficiency of UAV battery route flight and shortens the climbing time in the air.

(3) Exploring the application scenarios of the real-scene 3D model: this study extracted the skyline landscape on the north bank of the Huangpu River through the data of the urban 3D real-scene model, and used the real-scene 3D model for measurement and scheme design in the preparation of the building protection and repair plan of Shanghai Building, which enriched the Application scenarios of real-world 3D models.