Referring to your question, I understand that you're observing a discrepancy between the EPSG:3003 coordinate conversion results obtained using MATLAB's “projfwd” function and those from an online tool like EPSG.io.
Specifically, your MATLAB code yields:
posEPSG3003 = [1680827.953610798, 4851292.727994160];
whereas EPSG.io provides:
posEPSG3003 = [1680850, 4851220];
This discrepancy arises due to differences in the transformation parameters and methods used by MATLAB and EPSG.io. MATLAB's “projcrs” and “projfwd” functions rely on the PROJ library, which may use different default transformation paths or parameters compared to those employed by EPSG.io. These differences can lead to variations in the projected coordinates.
This documentation indicates that MATLAB is using PROJ library for conversion:
For more clarifications refer to following documentation links:
- projlist : https://www.mathworks.com/help/map/ref/projlist.html
- Projcrs : https://www.mathworks.com/help/map/ref/projcrs.html
- Projfwd: https://www.mathworks.com/help/map/ref/projcrs.projfwd.html
- PROJ: https://proj.org/en/stable/resource_files.html
For version specific MATLAB documentation links type following commands in MATLAB command window:
web(fullfile(docroot, '/map/ref/projlist.html'))
web(fullfile(docroot, '/map/ref/projcrs.html'))
web(fullfile(docroot, '/map/ref/projcrs.projfwd.html'))
Hope this helps you!
