Background With the rapid development of civil small drone photogrammetry technology, a large amount of field work has been gradually shifted to internal work in the field of soil and water conservation monitoring.Inthis article, a simple and efficient area measurement method with certain accuracy was explored based on UVA photography, aiming to solve the time-consuming problem to obtain digital orthophoto (DOM) in production with a relatively large storage capacity.

Methods A surface soil storage site in a soil and water conservation monitoring project on a highway in Guangxi province was selected as the experiment area, and the DJI Phantom 4 Pro drone was used to conduct surface observations at different altitudes. The relationship between the viewport area, the viewport length and the viewport width were quickly determined the scale of a single low-altitude aerial image, so as to achieve the purpose of quickly measuring the length and area of points of interest, eliminating the need to generate DOM.

Results The UAV flying height had a strong correlation with the viewport area, viewport length, and viewport width. R² was both 0.999, and the flight height was approximately equal to the viewport width.Using the regression equation formula and according to the law of the benchmark length and the height was approximately equal to the viewport width, the length information of the point of interest was calculated and the accuracy was verified. The accuracy of the 3 methods was: Benchmarking method (94.03%)>law of flying height = viewport width (93.97%)> formula method (92.18%), the data accuracy rate is >90%.

Conclusions The method of using UAV to quickly measure the area proposed in this paper is of high feasibility. In actual operation, it reduces working time and data redundancy, and thus improves work efficiency. It is also provide a feasible method reference to calibrate the related parameters of UAV. The research results provide a reliable method reference for UAV photography technology in the field of soil and water conservation monitoring.