In order to explore the effect of multispectral data of unmanned aerial vehicles(UAV)acquired at differ-ent time on the estimation of canopy chlorophyll density(CCD)of maize,the UAV multispectral observation experi-ment was conducted at 10:00-10:59,11:00-11:59,13:00-13:59,14:00-14:59 at the tasseling silking stage,blister stage,milk stage and dough stage,respectively.The PROSAIL model simulation results and the meas-ured CCD data were combined to analyze the changes of the typical vegetation indexes at different time of the day and the difference between the CCD estimation results.The results showed that both the canopy reflectance and the value of vegetation indexes strongly correlated with the measured CCD changed with the time on the same day.The most obvious change of reflectance was found in the near-infrared band on the same day.The vegetation index value de-creased as it approached 12:00 in the noon,whereas the value of vegetation indexes simulated by PROSAIL model at different time of the day showed little difference.The correlation between the same vegetation index obtained at dif-ferent observation time and the measured CCD was different on the same day,and the difference between growth sta-ges and indexes was not consistent;while the correlation between the same simulated vegetation index and CCD was not obvious at different time on the same day.CCD estimation models based on UAV data at different observation time could achieve good accuracy at different growth stages,but the estimation results at different observation time were different,with the lowest determination coefficient(R2)of 0.53 and the highest R2 of 0.80.These results showed that the traditional spectral data acquisition time range(10:00-14:00)had an impact on CCD estimation of maize,and the closer to the noon(12:00),the higher the estimation accuracy.These results provided basic sup-port for the accurate CCD estimation of crops.
维普
万方数据