Characteristics of close-range photogrammetry

Close-range photogrammetry refers to photogrammetry using stereo images taken by objects with a distance of not more than 300m m m.

In the steel rolling production line, in order to improve the production efficiency and product quality, a measuring camera is installed to measure the size and shape of the processed object in real time and guide the equipment to process the billet. In this way, the technology of shooting the target image at close range (generally within 100 meters) and determining its size, shape and geometric position after processing is called close-range photogrammetry.

The processing methods of close-range photos are divided into simulation method and analytical method. The simulation method is to measure the isoline and elevation of the photographed object with the help of a stereo mapper, and the result form is single. Analytical method is the main method, which can process photos taken by various cameras and provide high-precision results. Moreover, with the help of computers and plotters, contour maps (as shown in the figure), cross-sectional maps and three-dimensional perspective views can be drawn, and various parameters required by engineering designers, such as area, volume, perimeter, curvature, radius, speed, acceleration, trajectory and mass distribution, can be output in digital or graphic form. Close-range photos can be processed by various single images or three-dimensional coordinate measuring instruments, analytical surveying instruments and some three-dimensional surveying instruments, and there are also special close-range photogrammetry instruments.

The cameras used in close-range photogrammetry can be roughly divided into measuring cameras and non-measuring cameras. According to the structure, the camera used for measurement can be divided into single camera and stereo camera with fixed length baseline. The distortion of the objective lens is generally controlled within a few microns, and the internal orientation elements can be accurately recorded. Some cameras are also equipped with external orientation equipment, synchronous photography equipment and continuous photography equipment. Non-measuring cameras include general cameras, movie cameras and general high-speed cameras. This kind of camera generally has low imaging quality, unknown internal orientation elements and no external orientation equipment. When used to measure the target, the directional positioning mainly depends on a large number of evenly distributed control points, or the necessary verification is carried out in advance according to the situation.