Creating a GeoTIFF with 3 large matrices (Latitude, Longitude, Data) [satellite images]

Dear all,

I am trying to create a GeoTIFF from 3 matrices, each of 2000x2048. Let's call them:

Lat = 2000x2048

Lon = 2000x2048

Data = 2000x2048

Now, being the coordinates not equally spaced accross the scene, I cannot use the approach where xmin xmax ymin ymax define the 4 corners.

I can do that, but when I export the file to a GeoTIFF, this is wrongly georeferenced, resulting in something "flat" like this (assuming x and y axis had coordinates):

What I am after is exactly what geoshow does. For example I can obtain the image below from:

geoshow(Lat,Lon,Data,'DisplayType', 'surface') 
colormap jet, clim([250 320]), colorbar;

And this is what I get:

Now, how can I create something like this, that can be exported as a GeoTIFF?

*Please note, I tried to create meshgrids but unsurprisingsly I get the following error:

Requested 4096000x4096000 (125000.0GB) array exceeds maximum array size preference (13.9GB). This might cause MATLAB to become
unresponsive.

Any help would be much appreciated!

Answer 1

[Ashutosh Thakur]

Hi Simone,

I can understand that you want to export a GeoTIFF file, You can follow the below suggestions in achieving this objective:

• Create a Spatial Referencing Object using "georasterref" or "georefcells" based on latitude and longitude matrices.
• Also determine the geographic extent of your data based on the minimum and maximum latitude and longitude values.
• Now write the data to a GeoTIFF file using "geotiffwrite" function.

You can take reference from the below mentioned pseudocode:

% Example dataincluding latitude and longitude
Lat = ...; 
Lon = ...; 
Data = ...; 
% georastreff
R = georasterref('RasterSize', size(Data), ...
    'LatitudeLimits', [min(Lat(:)), max(Lat(:))], ...
    'LongitudeLimits', [min(Lon(:)), max(Lon(:))]);

% Define geographic extent
extent = [min(Lon(:)), max(Lon(:)), min(Lat(:)), max(Lat(:))];

% Write data to GeoTIFF
geotiffwrite('output_file.tif', Data, R, 'GeoKeyDirectoryTag', extent);

Also kindly refer to the following documentation links regarding "georasterref" or "geotiffwrite" operations:

• https://www.mathworks.com/help/map/ref/georasterref.html
• https://www.mathworks.com/help/map/ref/georefcells.html
• https://www.mathworks.com/help/map/ref/geotiffwrite.html

I hope this helps.

Thanks.