Analysis of image processing technology in basic surveying and mapping engineering?

1 "Large-scale basic surveying and mapping project" and "UAV image"

1. 1 Large-scale basic surveying and mapping project. Basic surveying and mapping project refers to measuring a certain interval and space, or measuring the land and area of a certain area, and drawing topographic maps through various effective information and data measured. In our place, topographic maps are usually drawn before some large-scale projects are built, or basic aerial photography is carried out when virgin land (uncultivated land or unexplored fields) is developed to obtain remote sensing data of basic geographic information.

1.2 UAV image. UAV image refers to the remote sensing image of UAV. Under the new situation, UAV remote sensing is one of the development trends of remote sensing. The reason why UAV remote sensing image technology has been widely used and developed is mainly reflected in two aspects: ① UAV remote sensing image technology application system has many advantages, low operating cost and strong flexibility in performing tasks. ② UAV remote sensing image application technology exists and develops as a supplement to satellite remote sensing and aerial remote sensing, because UAV has many functions that satellite remote sensing and aerial remote sensing do not have. Characteristics of UAV's influence: As mentioned earlier, compared with conventional manned aerial airplanes, UAV's camera is miniaturized and non-specialized, and its flying platform is low, which is its unique characteristics and advantages in a certain sense. Its specific advantages are as follows: the types of drones are diversified, and the cameras are also diversified. Therefore, the quality of image information and data obtained by different types of UAVs equipped with different types of cameras is also different. Small image, true color and high resolution are the common characteristics and advantages of UAV images.

2 UAV image processing application technology

2. 1 space three encryption application technology. As for aerial photography three encryption, aerial photography three encryption is the focus of UAV image processing technology in China, and it is also the most difficult point in the whole workflow. Its quality and degree directly affect the accuracy of subsequent results. In the early stage of the development of UAV image processing technology in China, aerial photography encryption was the main bottleneck in the process of large-scale basic surveying and mapping engineering. Later, through the comprehensive application of a number of related advanced technologies and scientific treatment methods and strategies, this problem was solved. At present, PixelGrid is widely used in aviation 3D encryption, which is a high-resolution integrated mapping system for remote low-altitude remote sensing images developed and manufactured by China Academy of Surveying and Mapping.

2.2 image data preprocessing of large-scale basic surveying and mapping engineering. In the process of aerial surveying and mapping, the cameras used in UAV images are basically non-metric cameras, so the edges of the images taken by them have optical distortion. The so-called distortion phenomenon can be seen from Figure E. The optical distortion of the edge of this image photo changes the actual terrain position of the photographed area and so on. Therefore, data preprocessing in the process of basic surveying and mapping can better correct image pictures.

2.3 image distortion correction. As mentioned earlier, image distortion is different from traditional aerial photography. The low-altitude remote sensing platform we use is usually equipped with non-metric cameras. At present, in the process of large-scale basic surveying and mapping engineering in China, in the application field of UAV image processing technology, common civil SLR cameras such as 500D and 5DMarkII are widely used, and fixed-focus lenses are used to shoot in the air. Under the influence and action of these factors, the images and photos taken by unmanned aerial vehicles are distorted to varying degrees, as shown in Figure E. Therefore, in order to weaken and reduce the errors caused by the distortion of non-measurement cameras in the process of surveying and mapping, we take the following necessary corrective measures. The modified model is as follows: ① δ x = (x-x0) (k1R2+K2R4)+p1[R2+2 (x-x0) 2]+2p2 (x-x0) (y-y0)+α (x-x0). 0) X and Y in Formula ① and Formula ② respectively represent the coordinates of the image point in the pixel coordinate system, K 1 and K2 are image distortion coefficients, and P 1 and P2 represent decentering distortion coefficients. Recover by calculation.

In large-scale basic surveying and mapping projects, more topographic maps and other related data can be obtained by using UAV image processing technology. The UAV itself has the advantages of motorization and rapid aerial photography, so the images obtained also have the characteristics of high resolution. In the application process, some technical measures are very important, which can help improve the efficiency of aerial survey of unmanned aerial vehicles and better provide services and guarantees for relevant departments to carry out large-scale basic surveying and mapping projects.

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