Study On Total Grassland Coverage Measurement Method Based On Digital Photography

In grassland monitoring and evaluation,grassland coverage measurement method directly affects the accuracy of the results.The test from the resolution?24M,14 M,12M,10 M,9M and 8M?,shoot height?1.36 m,1.43 m,1.49 m?and light intensity?9AM 10 AM,12AM¹5PM,16 PM¹8PM?,factors influencing the photos taken with Photoshop?PS?and MATLAB processing photo coverage values?P >0.05?,point measuring method is used to test the grass coverage.The general estimation model of no-mowing and mowing was established by stepwise regression analysis,aiming at providing convenient coverage survey method for future field investigation of grassland plant community.The results showed that:1.In the sample plot without mowing,24 million pixels were applied,and the shooting time period was 9AM 11 AM and 16 PM 18 PM,and the shooting height was 1.46 m.The estimation accuracy of the coverage photos was the best.2.In the clipped sample plot,24 million pixels were applied,and the shooting time was 9AM 11 AM,and the shooting height was 1.46 m.The estimation accuracy of the coverage photos was the best.3.The coverage value of MATLAB is less affected by light intensity than that of PS,which is more suitable for the extraction of photo coverage.4.The general model for estimating grassland was established by using stepwise regression analysis for influencing factors of different resolutions,shooting heights and time periods: Y=?1.042e-5?X₁-?2.5e-6?X₂+?6.25e-6?X₃+15.946,R=0.935,R²=0.874,P < 0.0001.X₁ is the total number of green pixels in the coverage photo taken at 24 million pixels;X₂ is the total number of green pixels in the coverage photos taken from 9AM ¹1AM;X₃ is the total number of green pixels in the coverage photo taken at 1.46m;E is the base value of natural logarithm,2.71828.The estimated accuracy is up to 93.73%.Excluding August and September when the deviation is within 5%,the model is modified,and the modified estimation model is as follows: Y₅=?1.042e-5?X₁-?2.5e-6?X₂+?6.25e-6?X₃+2.596;Y₆=?1.042e-5?X₁-?2.5e-6?X₂+?6.25e-6?X₃+10.496;Y₇=?1.042e-5?X₁-?2.5e-6?X₂+?6.25e-6?X₃+15.396;Y₁₀=?1.042e-5?X₁-?2.5e-6?X₂+?6.25e-6?X₃+19.416.The mean deviation between the estimated value of the model andthe measured value is less than or equal to 5.16%,which proves that it can be used in the survey of grassland community.