Abstract: The aerial photogrammetry technology of UAV makes traditional forest survey methods develop towards digitalization and intelligence. In order to improve the precision and efficiency of forest resource information collection, reduce field work time and work intensity, the method and precision of obtaining forest resource data by UAV stereo photography technology are studied in this paper. A three-dimensional stereo image of the study area was acquired by using a rotorcraft equipped with a five-eye camera. The tree height, three-dimensional coordinates, crown width, and area were extracted from the image by software. All these was y=0.998 9x+0.068 5, the correlation coefficient R²=0.98,indicating a high precision of crown width obtained by UAV stereo photography. The true error interval of the three-dimensional coordinate positioning was between -13 and 17, in which the discrete interval of the elevation coordinate was greater than the planar coordinate, the precision of the planar coordinate is about 3 cm, while elevation coordinate is about 10 cm. The sample area values obtained by the stereo photography technology were close to true values and the correlation coefficient is 0.98. It could be obtained that the UAV stereo photography technology had a high precision of obtaining forest resource information data, which improved efficiency, saved costs, reduced work intensity, and had higher practical promotion value.

Key words: unmanned aerial vehicle (UAV), 3D photography, measure, tree characteristic factors, precision