extracting lat/lon from tif file using matlab

I have a tif file with a map of locations that has data. I want the lat/lon of that locations using matlab.

I ploted that in matlab using this code

[tifImage, R] = geotiffread('NA_CONUS_border.tif');

>> tifImageDouble = double(tifImage);

>> figure;

mapshow(tifImageDouble, R);

title('Georeferenced TIFF Image');

locations with data has [R,G,B]=[1 1 1].

I want to Convert pixel coordinates to geographic coordinates [lat lon].

does anyone have any idea how to do that?

[Dyuman Joshi]

It's not clear to me what you want to do.

Do you want the geographic coordinates for the pixels whose color is white? If yes, could you attach the tif file?

If not, then please clarify.

[Seyedeh Fardis]

Yes. I want the the geographic coordinates for the pixels whose color is white.

[Star Strider]

The geotiffread funciton is no longer recommended. It has been replaced by readgeoraster (introduced in R2020a) and that documentation illustrates how to get the latitude and longitude information from the file.

[Dyuman Joshi]

@Seyedeh Fardis Please attach the tif file (as asked earlier as well).

And mention which version of MATLAB you are using.

[Seyedeh Fardis]

I'm using R2020a .

Answer 1

[Cris LaPierre]

See this answer, which was updated in 2022.

https://www.mathworks.com/matlabcentral/answers/8865-geotiffread-getting-latlon-info

I will mention that I did have to set the 'OutputType' to get it to work.

unzip("NA_CONUS_border.tif")

% Read image file using readgeoraster
fname = "NA_CONUS_border.tif";
[A,R] = readgeoraster(fname,"OutputType","double");
mapshow(A,R)

% Create grid of X,Y values
[x,y] = worldGrid(R);

% Convert grid of X,Y values to latitude/longitude
[lat,lon] = projinv(R.ProjectedCRS,x,y);

% Extract lat/lon locations of white line
NA_lat = lat(A==1);
NA_lon = lon(A==1);

% Plot extracted latitude/longitude on geographic axes
figure
geoscatter(NA_lat,NA_lon,'.')
geobasemap satellite
title("geographic axes")

[Seyedeh Fardis]

Thank you for that! does tif file contain data as well? I have a dataset and I want to see which data is for which node. I'm not sure if that data is available is tif file as well. if yes, how I can load then in matlab in ordeer of lat/lon?

[Cris LaPierre]

You could check what information is available using geotiffinfo

Answer 2

[DGM]

I never really use mapping stuff, so take this with a grain of salt.

fname = 'NA_CONUS_border.tif';
[tifImage, R] = geotiffread(fname);
S = geotiffinfo(fname);

tifImage = double(tifImage); % contains unique values [0 1 2] (a label array??)
mapshow(tifImage, R);
title('Georeferenced TIFF Image');

% get pixels that are exactly 1
% this ignores the fact that pixels >1 will also be white.
% adjust the test accordingly
[row col] = find(tifImage == 1);

% convert to lat/lon
[x y] = pix2map(S.RefMatrix,row,col);
[lat lon] = projinv(S,x,y);

[Seyedeh Fardis]

Thank you for that! does tif file contain data as well? I have a dataset and I want to see which data is for which node. I'm not sure if that data is available is tif file as well. if yes, how I can load then in matlab in ordeer of lat/lon?