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Read/write georeferenced image

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Massimo Zanetti
Massimo Zanetti on 28 Sep 2022
Answered: Yan Tong on 16 Aug 2023
Hi, here I am wondering why this simple operation of reading a georeferenced .tif image and writing some results in the same georeferenced framework is so difficult. Here is my example:
[A,R] = readgeoraster("input_image.tif");
O = f(A) %any operation you like
This gives the error:
Error using geotiffwrite
The input, R, is a map.rasterref.MapCellsReference object indicating that you are working in a projected coordinate system. If so, then specify a projected coordinate system by setting the appropriate values for the 'CoordRefSysCode' or 'GeoKeyDirectoryTag' optional parameters.
But the input image includes the Coordinate Reference System Code (which is EPSG:32632), and the geotiffinfo function confirms that, as I have among other values: PCS: WGS 84 / UTM Zone 32N, which is the same as EPSG:32632.
So, do we have two Matlab functions incompatible each other? How am I supposed to automatically save the result without manually input 'CoordRefSysCode',32632 to the geotiffwrite function?

Accepted Answer

Kevin Holly
Kevin Holly on 28 Sep 2022
Can you try this below?
[A,R] = readgeoraster('input_image.tif');
O = A*2; %any operation you like
info = geotiffinfo('input_image.tif');
key = info.GeoTIFFTags.GeoKeyDirectoryTag;
  1 Comment
Massimo Zanetti
Massimo Zanetti on 29 Sep 2022
Thank you Kevin, this works fine, of course. The same would be using 'CoordRefSysCode',info.GeoTIFFCodes.PCS
I find it strange that readgeoraster function is not able to handle it on its own. It is indeed supposed to read georeferenced data but it cannot resolve projections. Working with georeferenced images, having them projected is the most common situation. This probably requires a fix.
Thanks again,

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More Answers (1)

Yan Tong
Yan Tong on 16 Aug 2023
You can try this!
[A,R] = readgeoraster(infilename);
info = geotiffinfo('input_image.tif');
geoTags = info.GeoTIFFTags.GeoKeyDirectoryTag;
tiffTags = struct('TileLength',1024,'TileWidth',1024);
geotiffwrite(outfilename,your_outputtiff,R,'TiffType','bigtiff', ...
'GeoKeyDirectoryTag',geoTags, ...

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