[PROJ] Use of EPSG codes in proj_create()

[Kristian Evers]

To be honest I am leaning towards killing the migration guide. It was an attempt at making
it easier to move from proj_api.h to proj.h but since it was written a lot have happened
and the premise has changed. Instead I would rather write a couple of proper pages
demonstrating the use of the current API. If done properly it should be sufficient help
for those migrating old code to use the new API and will be better suited for newcomers.

But it raises the question: What sort of things will be useful to demonstrate on doc pages
like that? 

/Kristian

> On 2 Apr 2019, at 20:59, Oliver Eichler <oliver.eichler at dspsolutions.de> wrote:
> 
>> PROJ master (future 6.1.0) has a new proj_normalize_for_visualization()
>> function that takes a pedantic-axis-order compliant PJ object (returned by
>> proj_create_crs_to_crs()) and add the needed axis swapping to get the
>> traditional GIS friendly order.
> 
> sounds promising. Will there be an example in the migration guide? Right now this guide is pretty frustrating. It gives you a rough example of something that does not even match the old behavior and the rest is "find out yourself". No documentation in the headers. No obvious link to API documentation on the web page. Yes, I found it by chance using Google. I don't want to complain too much, but so far the migration is more a PITA than anything else.
> 
> It would really help to have example code to restore the old complex functions like pj_transform(). Keep in mind that you introduced quite some pitfalls that will break the software using PROJ silently. The moment a user uses a CRS that does it different the software will fail leading to a bug report, a lot of investigation why it breaks, the realization that new PROJ introduced inconsistencies (from the user's point of view) and finally patching the software that uses PROJ over and over again. This will be a very frustrating experience for every party involved.
> 
> Would that be possible?
> 
> Oliver
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