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<p>Hello Floris</p>
<p>If a choice is possible, I would encourage to use one of the
approaches recognized by international standards:</p>
<ul>
<li>Authority codes with axis order and units as defined by
authority (e.g. "EPSG:4326" is <i>latitude</i>, <i>longitude</i>;
if the reverse order is wanted then "CRS:84" can be used
instead).</li>
<li>Well Known Text version 2 (a.k.a. ISO 19162).</li>
<li>Possibly the JSON format cited by Even in the future.</li>
</ul>
<p>PROJ 6 and later support all the above. I think they are
preferable to PROJ strings for at least 2 reasons:</p>
<ul>
<li>They are portable, with WKT 2 possibly the safest bet for
now since it is an existing OGC and ISO standard. While PROJ
is the most popular, it is nevertheless not the only map
projection engine available, with each engine having their
advantage and inconvenient. Other map projection engines are
more likely to understand a CRS defined by international
standards than by PROJ-specific strings. Even if R uses only
PROJ, a R script may want to fetch data from a distant server
backed by a different map projection engine.</li>
<li>For educational reason: the PROJ string syntax evolved from
a system initially designed for map projections only, not for
the more general context of transformations between arbitrary
pairs of CRS. If users educate themselves by learning from
PROJ strings, there is a risk that they confuse CRS with
operations, that they believe that "+towgs84" is good
practice, etc.<br>
</li>
</ul>
<p>Regards,<br>
</p>
<p> Martin</p>
<p><br>
</p>
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