在应用年内的NDVI信息的时候，由于云的干扰，通常需要对NDVI产品如MOD13A2进行滤波处理进行重建，本文基于matlab平台，结合SG滤波和质量控制文件对MOD13A2产品进行重新构建，基本思路是首先对23期数据进行滤波处理，然后质量好的像元保持不变，而质量较差的像元为滤波后的值，构成新的NDVI序列?；敬肴缦?/p>
% @author yinlichang3064@163.com
[a,R]=geotiffread('I:\MOD13A2\MOD13A2_yr_03-17_16DAY\NDVI_PR_2017353.hdfout.1_km_16_days_NDVI.tif');
info=geotiffinfo('I:\MOD13A2\MOD13A2_yr_03-17_16DAY\NDVI_PR_2017353.hdfout.1_km_16_days_NDVI.tif');
[m,n]=size(a);
begin_year=2001;
end_year=2018;
qs=23;
%总共23期数据
for year=begin_year:end_year
ndvisum=zeros(m*n,qs)+NaN;
qcsum=zeros(m*n,qs)+NaN;
k1=1;
for k=1:16:366
if k<10
filename=['I:\MOD13A2\MOD13A2_yr_03-17_16DAY\NDVI_PR_',int2str(year),'00',int2str(k),'.hdfout.1_km_16_days_NDVI.tif'];
filename_pr=['I:\MOD13A2\MOD13A2_yr_03-17_16DAY\NDVI_PR_',int2str(year),'00',int2str(k),'.hdfout.1_km_16_days_pixel_reliability.tif'];
else
if k<100
filename=['I:\MOD13A2\MOD13A2_yr_03-17_16DAY\NDVI_PR_',int2str(year),'0',int2str(k),'.hdfout.1_km_16_days_NDVI.tif'];
filename_pr=['I:\MOD13A2\MOD13A2_yr_03-17_16DAY\NDVI_PR_',int2str(year),'0',int2str(k),'.hdfout.1_km_16_days_pixel_reliability.tif'];
else
filename=['I:\MOD13A2\MOD13A2_yr_03-17_16DAY\NDVI_PR_',int2str(year),int2str(k),'.hdfout.1_km_16_days_NDVI.tif'];
filename_pr=['I:\MOD13A2\MOD13A2_yr_03-17_16DAY\NDVI_PR_',int2str(year),int2str(k),'.hdfout.1_km_16_days_pixel_reliability.tif'];
end
end
ndvi=double(importdata(filename));%获取ndvi
ndvi=reshape(ndvi,m*n,1);
ndvi(ndvi==-3000)=NaN;
qc=importdata(filename_pr);%获取ndvi的质量文件
qc=reshape(qc,m*n,1);
ndvisum(:,k1)=ndvi;
qcsum(:,k1)=qc;
k1=k1+1;
end
for i=1:m*n
data1=ndvisum(i,:);
if min(data1)>=-2000
qc=qcsum(i,:);
data_sg=sgolayfilt(data1,3,5);
data_sg(qc==0)=data1(qc==0);%进行还原
ndvisum(i,:)=data_sg;
end
end
for k=1:qs
ndvi=ndvisum(:,k);
ndvi=reshape(ndvi,m,n);
ndvi(ndvi<-2000)=NaN;
filename=['I:\MOD13A2\MOD13A2_yr_03-17_16DAY\基于质量文件和SG滤波插补\MOD13A2_',int2str(year),'_',int2str(k),'.tif'];
geotiffwrite(filename,ndvi,R,'GeoKeyDirectoryTag',info.GeoTIFFTags.GeoKeyDirectoryTag)
end
end
在用上述代码的时候请引用以下文献:
Yin, L.; Wang, X.; Feng, X.; Fu, B.; Chen, Y. A Comparison of SSEBop-Model-Based Evapotranspiration with Eight Evapotranspiration Products in the Yellow River Basin, China. Remote Sens. 2020, 12, 2528.
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