How to retrieve multiband data using shape file?
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I have kept the data and shape file on following link
I am using the code for extracting seven band data as follows;
% Get image info:
DataFile='C:\working_bpt\bands\Bagpat_7Bands.dat'
[Z,R] = readgeoraster(DataFile);
disp(size(Z));
p = R.ProjectedCRS;
[x,y] = worldGrid(R);
[lon,lat] = projinv(p,x,y);
ShapeFile='C:\working_bpt\bands\BAGHPAT.shp'
S = shaperead(ShapeFile);
info = shapeinfo(ShapeFile);
crs = info.CoordinateReferenceSystem;
[S(1).lon,S(1).lat] = projinv(crs,S(1).X,S(1).Y);
% Remove trailing nan from shapefile
rx = S(1).lon(1:end-1);
ry = S(1).lat(1:end-1);
logical_mask = inpolygon(S(1).lon,S(1).lat,rx,ry);
% Use the logical mask to extract data
extracted_data = Z(logical_mask);
disp(extracted_data);
it is giving following informations
DataFile =
'C:\working_bpt\bands\Bagpat_7Bands.dat'
5490 5490 7
ShapeFile =
'C:\working_bpt\bands\BAGHPAT.shp'
disp(size(extracted_data));
1 9
OR
ShapeFile =
'C:\working_bpt\bands\BAGHPAT.shp'
disp(extracted_data);
1794 1842 1829 1858 1934 1968 2315 2635 2578
My target is to retrieve the data from seven band data of dimensions
number of lines = 5490
number of samples = 5490
number of bands =7
and dimensions of output file are supposed to be
number of lines =1153
number of samples = 1315
number of bands =7
I request you to kindly look on it and suggest me how to get seven band data using shape file.
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Answers (1)
Samay Sagar
on 29 Jul 2024 at 4:16
To extract data from the seven-band image using the shapefile, you can follow these steps. This will involve reading the image data, using the shapefile to create a mask, and applying this mask to extract the relevant data from the image. Here is how you can do it:
% Load the synthetic image data
load('sample_image.mat', 'Z', 'R');
% Read the shapefile
ShapeFile = 'sample_shapefile.shp';
S = shaperead(ShapeFile);
% Use shapefile coordinates directly
x = [S.X];
y = [S.Y];
% Remove trailing NaN from shapefile
x = x(~isnan(x));
y = y(~isnan(y));
% Convert shapefile coordinates to pixel indices
row = floor((y - R.YWorldLimits(1)) / R.CellExtentInWorldY) + 1;
col = floor((x - R.XWorldLimits(1)) / R.CellExtentInWorldX) + 1;
% Create a mask from the polygon
logical_mask = poly2mask(col, row, size(Z, 1), size(Z, 2));
% Initialize extracted data array
extracted_data = zeros([sum(logical_mask(:)), size(Z, 3)]);
% Extract data from each band
for band = 1:size(Z, 3)
band_data = Z(:,:,band);
extracted_data(:, band) = band_data(logical_mask);
end
disp(size(extracted_data));
disp(extracted_data);
For more information about “poly2mask” , you can refer the following documentation:
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