One of the main purposes of calibrating aerial cameras is to accurately obtain the value of the camera ().

One of the main purposes of calibrating an aerial camera is to accurately obtain the value of the camera (internal orientation element).

Aerial photography is the whole process of taking airplanes or balloons as remote sensing platforms, using aerial cameras carried in the air to reach the ground, collecting and processing target information through photography, and obtaining various images and data. The sensors used in photography mainly include aerial cameras and multispectral cameras.

Photographs obtained by photography have the characteristics of large amount of information and high resolution, and can also obtain spectral radiation of ground objects from visible light to near infrared. However, due to the limitation of emulsion, only near ultraviolet, visible light and near infrared spectral information with wavelength of 0 can be obtained. 3 ~ 1.3 can obtain micron, and imaging can only be carried out in daytime.

(1) Type of photo

According to the relationship between the main optical axis of aerial camera and the vertical line, aerial photography can be divided into vertical photography and oblique photography. Vertical photography means that the main optical axis of the aerial camera is kept in the vertical direction, and the maximum included angle with the vertical line does not exceed 3, and the obtained photos are called horizontal aerial photos; If the included angle exceeds 3, it is oblique photography, and the obtained aerial photograph is called oblique aerial photograph.

According to the task and purpose, aerial photography can be divided into single photo photography, strip aerial photography and regional aerial photography.

According to the height of aerial remote sensing platform, it can be divided into: aerial photography (platform height above 9km); Aerial photography (height 6 ~ 9 km); Low-altitude photography (height less than 6 km). Low-altitude and high-altitude remote sensing, with small imaging scale and large coverage, is suitable for large-scale census; Low-altitude aerial remote sensing can obtain a wide range of images and is the most widely used remote sensing means at present.

According to the different photosensitive materials, it can be divided into full-color black-and-white photography, black-and-white infrared photography, color photography, color infrared photography and multi-spectral photography.

(b) Ground coverage and image overlap

In order to ensure the continuous coverage and stereoscopic observation of aerial photography, some images overlap between adjacent photos (Figure 3-29), and they overlap symmetrically along the route direction, and the overlap rate is required to reach 60% or not less than 53%. Two adjacent photos with this overlapping relationship are called stereo image pairs. The image overlap between two adjacent routes is called lateral overlap, and the overlap rate is usually 20% ~ 30%. The terrain fluctuates greatly, and the overlapping rate should be improved accordingly.