How to make a logical mask using a shape file?

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Devendra on 26 Mar 2024

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Commented: Image Analyst on 28 Mar 2024

I am using following MATLAB code to create logical mask.

 % Create a logical mask
    [Z,R] = readgeoraster(img_file.name);
    disp(R);
    [lat,lon] = geographicGrid(R);
    [Lon, Lat] = meshgrid(lon, lat);
    logical_mask = reshape(isinterior(polygon, Lon(:), Lat(:)), size(Lon));

It is giving following erros

Incorrect number or types of inputs or outputs for function geographicGrid.

Error in ds_indices_caf (line 57)

[lat,lon] = geographicGrid(R);

I request to kindly suggest me how to do it correctly.

Dava

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Answers (1)

Image Analyst on 26 Mar 2024

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https://se.mathworks.com/matlabcentral/answers/2099311-how-to-make-a-logical-mask-using-a-shape-file#answer_1431561

You have to define lat and lon as vectors before you use them in meshgrid to get the full matrices Lat and Lon as outputs.

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Image Analyst on 27 Mar 2024

Open in MATLAB Online

It looks like it probably requires the Mapping Toolbox, which I do not have. Does it?

help geographicGrid
--- help for map.rasterref.GeographicCellsReference/geographicGrid ---

  geographicGrid - Geographic coordinates of raster elements
 
    [LAT,LON] = geographicGrid(R) returns the locations of
    raster elements in geographic coordinates as 2-D arrays,
    LAT and LON. When R is a GeographicCellsReference object,
    the locations are cell centers. When R is a
    GeographicPostingsReference object, the locations are
    posting points. The location of raster element (i,j) is
    (LAT(i,j), LON(i,j)). The values of size(LAT) and size(LON)
    both equal the RasterSize property of R.
 
    [LAT,LON] = geographicGrid(R,gridOption), where gridOption
    is 'gridvectors', returns LAT and LON as row vectors. The
    location of raster element (i,j) is (LAT(i), LON(j)). The
    value of [length(LAT) length(LON)] equals the RasterSize
    property of R. The default for gridOption is 'fullgrid'.
    geographicGrid(R,'fullgrid') is equivalent to
    geographicGrid(R).
  
    Example
    -------
    R = georefpostings([0 30],[-20 20],[4 5])
    [lat,lon] = geographicGrid(R)
    [lat,lon] = geographicGrid(R,"gridvectors")

    Documentation for map.rasterref.GeographicCellsReference/geographicGrid
       doc map.rasterref.GeographicCellsReference/geographicGrid

Devendra on 27 Mar 2024

I have installed trial version of Matlab 2024a.

Deva

Image Analyst on 28 Mar 2024

I believe during the trial period you get free telephone help. Call them and work through it with an actual live person. I can't help you because I do not have that toolbox.

Products

Image Processing Toolbox

Release

R2024a

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