| we need solve the problems in our agricultural production,one is precise fertilization in a single field,the other is variable rate fertilization in different fields.Acquiring information of farmlands quickly and accurately is implementation of variable fertilization,spectral reflectance is a new spectrum analysis technology,which is the effective technological means in crop fertilizer stage.it use reflectance spectroscopy to get spectral reflectance indices and use crop nutrition diagnosis model to access crop nutrition information.now spectral reflectance measurement are main hand-held and vehicular,hand-held is use for sampling inspection,when it measured,it cost many time,so it is suitable for application in research activities,not suitable for application in practical production.though vehicular can acquire crop nutrition information,in order to avoid second crop damage,we usually control the operation of variable rate fertilization in real-time measurement,it can't achieve the ideal effect and satisfy precise fertilization in single field.we use UAV to build a crop canopy spectral reflectance test platform,which can quickly acquire crop nutritional status of the growth stage information and build field of crop growth information,at last it can guide variable rate fertilization.Research contents and results are summarized as blow:1.Set up a canopy spectral reflectance measurement platform base on UAV.it use the M100 which was made by DJM,and active light source spectral reflectance measuring instrument which was made by our lab.in order to match platform,we design the spectral reflectance measuring shell,finish light path system and installation of circuit module structure,ensure the light path system avoiding sunshine and interference between circuit and stability to ensure spectrometer stable.2.Improve the light source spectral reflectance measuring instrument.In order to meet the requirement of UAV reflection spectrum measurement platform,the spectral measuring instrument by our lab is improved,it include three aspects:(1)In order to satisfy requirement of platform and reduce the weight of platform,platform use UAV to supply the platform;(2)platform is joined the GPS positioning module of speed,it can get field location information,UAV speed information and flight trajectory;(3)considering spectrometer using many resources,so platform use double MCU,design the circuit which is receiving data and storing data for data acquisition and storage effectively.3.UAV canopy spectral reflectance measurement platform measure effectively and stably of test,it include three aspects:(1)Comparing with hand-held canopy spectral reflectance measurement experiment:choosing the hand-held canopy spectral reflectance measuring instrument which has been calibrated to compare the platform,a row of bar area 64m x 2.3m in the fields are selected for the test object,choose a measurement point every 10m,select five measurement and three measuring height which are 60cm,70cm and 80cm.hand-held canopy spectral reflectance measuring instrument and platform have high consistency under different measurement point and different measuring height,maximum average deviation of measurement point is 3.2%,maxium standard deviation is 2%,the results show platform is stable and effective.(2)Performance test of platform under the heeling condition:when UAV is flying,it is often impact external factors include wind speed,frequency interference and so on,then UAV will be heeled.In order to analysis Performance test of platform under the heeling condition,the platform must be heeling in all experiment and tilt angle is less than 45°,then test data and data under static condition are compared.The results show data under heeling is large than it in static condition,the maximum relative deviation is 4.4%,the maximum is standard deviation is 4.45%,it indicate the platform has a good resistance under heeling condition.(3)Performance test of platform under flying fix-point:when UAV is flying,it will produce wind field,then wind field will have larger disturbance on crop canopy,in order to analysis wind field weather impact experiment platform,UAV is fly upon crop,the height is in 60cm-100cm,compare test data with data under static condition.The results show data under flying and has high consistent with data under static condition,maximum relative error of measuring points is 4.4%,minimum relative error of measuring points is 0.57%,the maximum is standard deviation is 3.89%,the minimum is standard deviation is 0.48%,it show wind field has little effect,the platform can satisfy the dynamic measurement.4.Performance test of UAV canopy spectral reflectance measurement platform in field:in order to test under flying without people controlled weather is realized and analysis the NDVI in a single field and between different fields,then the platform will fly according to designer routes,two fields were chose,areas of them are 12m×68m and 18m×68m,areas of each is divided into four rows,every row is 68m and has five point,the distance of every point is 10m,then platform will measure without people controlled.the results show flight path of UAV are basically superposing,the results show that test under flying without people controlled can get nutritional rapid and efficient,it can provide the basis for implementing variable crop fertilization.NDVI is similar in the same field,the maximum average relative deviation is 4.12%,the largest standard deviation is 3.84%,there may be differences in two fields,the maximum average relative deviation is 4.61%,the largest standard deviation is 2.89%.NDVI in two fields of average deviation is 4.8%.it shows Autonomous flight acquisition can get nutrition of crops rapidly and efficient,it provide basis for crop fertilization. |
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