[Qgis-user] How to add custom system reference transformation data

[Dario]

Hi,
Probably my request will not be clear for not Italian people.

Premise:
I often use data in both 7791 and 3003.
I have converted base cartography from 7791 to 3003 using a proper software (ConveRgo by IGM). In this way I can add other layer from online library in 3003.

If I use 7701 base cartography and qgis’ native transformation data it means I could have 4meter approximation error. In the reality, in my case, I have around 70 cm from the one converted by Qgis and the one converted with the official converter from IGM.

Question:
As I have also several official .src file for conversion,
I’d prefer to add these file into Qgis and work directly with 7791 and 3003 file, having the same level of precision of real conversion using ConveRgo.

I tried reading some post and video, but without success.

Thank you 

Cheers 

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