Application Of UAV Aerial Survey Technology In Monitoring Of Small Watershed Comprehensive Management Measures In Taiyi Mountain Areas

In order to explore the technology and effect of UAV aerial survey applied to small watershed comprehensive management project monitoring.In this paper,three small watershed comprehensive management project areas in Yishui County,Linyi City,Shandong Province and three soil and water conservation forestation sites in Xintai City,Tai’an City were selected.Taking the soil and water conservation engineering measures and plant measures implemented as the research objects,the UAV aerial survey technology was used,combined with basic data collection and field sample survey,to monitor and study different soil and water conservation measures.Research purposes:1)to establish interpretation marks of soil and water conservation measures under different resolution images;2)to clarify the identification effect of different resolution images on Soil and water conservation measures;3)to analyze flight efficiency under different flight photography modes and flight altitudes.The main results and conclusion are as follows:1.Comprehensive control measure system of soil and water loss in small watershed of study areaThe system of comprehensive control measures for small watershed in the study area includes soil and water conservation engineering measures and plant measures.The engineering measures include slope terraces(soil ridge terraces and stone ridge terraces),reservoir,grit chamber,drainage ditch,channel weir and sand retaining dam,etc.;the plant measures include soil and water conservation forest and economic forest(fruit forest),and the tree species of soil and water conservation forest are Platycladus orientalis,Pinus thunbergii and Robinia pseudoacacia and the economic forest are chestnut and peach trees.2.Interpretation marks of soil and water conservation measures under different resolution images(1)Aerial survey image:obtain the orthophoto images of UAV in the project area under two shooting modes(hovering,equal time interval)and three flight altitudes(100m,150m and 200m).The resolution of UAV images under 100m,150m and 200m is 2.7-2.9cm,4.2-4.4cm and 5.5-5.8cm respectively.(2)Interpretation marks:the interpretation marks of soil and water conservation engineering measures and plant measures in different project areas and forestation sites were established under three kinds of flying altitude images,and the image characteristics of texture,color,shape and outline of interpretation marks of different soil and water conservation measures were defined.3.Identification effect of different resolution images on Soil and water conservation measures(1)Engineering measures:under the image of 200m flight altitude(resolution 5.5-5.8cm),various soil and water conservation measures can be distinguished,and the engineering plane parameters such as shape and size can be obtained.Therefore,the flight altitude of UAV aerial survey for identification of soil and water conservation engineering measures can be 200m.(2)Plant measures:the recognition effect varies with the image resolution,tree type and tree body(crown size).Under the 100 m flying height(resolution 2.7-2.9 cm)image,the plant species(coniferous and broad-leaved)and plant contour with the crown diameter greater than40 cm can be distinguished,and the specific deciduous tree species with the crown diameter greater than 160 cm can be distinguished,so it is difficult to distinguish the specific coniferous tree species.At 150 flight height(resolution 4.2-4.4cm),only conifers(Platycladus orientalis and Pinus thunbergii)with crown larger than 70cm can be distinguished.200m flight altitude(resolution 5.5-5.8cm)can not be distinguished.According to the above results,the flight altitude of UAV aerial survey for soil and water conservation plant measures identification should be less than 100m.4.Flight efficiency under different flight photo modes and flight altitudes.In hover mode,the flight efficiency of UAV is about 0.0075km~2/min,0.022km~2/min and0.0394km~2/min at 100m,150m and 200m altitude;in equal time interval mode,the flight efficiency is about 0.0103km~2/min,0.0225km~2/min and 0.054km~2/min at 100m,150m and200m altitude.It shows that the flight efficiency of UAV is positively related to the shooting height,and the flight efficiency of equal interval shooting mode is higher than that of hovering shooting mode.