Create new custom projections in QGIS 3.12?

Question

QGIS does not have the coordinate reference system I need, So I decide to define a new custom Geographic coordinate system. To define a CRS, I selected customProjection Custom CRS from the Settings menu. The Custom Coordinate Reference System Definition dialog requires only two parameters to define a user CRS: 1) A descriptive name 2) The cartographic parameters in PROJ.4 format

So I did that as you can see from the picture:

But when I click OK to add the projection within QGIS a pop up message with an error show up and with very different set of parameters in the parameter window. the error message says I have set up a proj string definition equivalent to esri:102218 which is not really the same. I don't really know if this a bug or something went wrong with my parameter setting.

Answer 1

Select the WKT Format (not the Proj String as shown in the question screenshot)

https://epsg.io/4919 copy text function

Then Validate

Answer 2

The problem is not with your new CRS, but with an old CRS defined before the upgrade to 3.12 version.

That CRS is a Generated CRS. In older versions, when you load a layer with an unknown CRS, a custom CRS was created.

Now, the ESRI authority was added to the PROJ database, custom CRSes are not automatically generated, and custom definitions that are equal to a known CRS are not allowed.

Just remove that old automatically generated CRS, you will not need it any more.