[PROJ] How to get started with CRS in WKT?

[Even Rouault]

Jochem,

Is "read the spec", the answer you expected ;-) ? I'm afraid that's the 
best I have: http://docs.opengeospatial.org/is/18-010r7/18-010r7.html

Regarding indentation, don't worry about that. Write your WKT as you can 
in a file and then use "projinfo @your.wkt", and it will return a nicely 
reformatted string. But you need to get brackets right, otherwise the 
parser will be lost.

You may also try the PROJJSON encoding as an input and feed it to 
"projinfo @your.json" and it will return a WKT, but I'm not sure it will 
help you, as it is more oriented to be machine friendly.

For CRS definitions themselves, it is unlikely you can use the 
transformation constructs if you intend to have your CRS in EPSG. 
ABRIDGEDTRANSFORMATION is only for BoundCRS, and they are none of them 
in EPSG. GEOGTRAN is a Esri WKT specific thing. COORDINATETRANSFORMATION 
is for a standalone CoordinateTransformation object

If your ultimate goal is to provide CRS and coordinate transformations 
to EPSG, then you don't need to create WKT. Go to 
https://epsg.org/dataset-change-requests.html and click on the "Template 
for data submission" link at the right of the page, and you'll get an 
Excel spreadsheet where you'll get a form with the decomposition of the 
objects.

Even

Le 05/12/2022 à 13:03, Lesparre, Jochem via PROJ a écrit :
>
> Dear PROJ maillist,
>
> At a the national mapping agency of the Netherlands we are responsible 
> for defining the CRS of European Netherlands and the 3 islands of the 
> Caribbean Netherlands. We are working on standardising the official 
> transformations so these can be added to EPSG and the transformations 
> become available in PROJ and other software. To perform 
> transformations ourself, we create cct pipelines. I love the power cct 
> pipelines. Unfortunately, other applications often expect a WKT 
> string. For the transformations we added to EPSG, I can copy-paste the 
> WKT from epsg.org. To experiment with a custom CRS, I sometimes try to 
> create my own WKT strings. However, these attempts are not very 
> successful for two reasons.
>
> Firstly, it takes an annoying lot of effort get the code indented to 
> make it readable (the indent plugin in notepad++ only works after 
> using search and replace to add line breaks) and to keep the brackets 
> right for valid WKT while editing, before I can even start to 
> experiment with the rest of the syntax. /Can you recommend a way to 
> make creating WKT easier?/
>
> Secondly, I am quite confused by the different WKT examples that I 
> find. Some seem to use different ways to define transformations in WKT 
> (e.g. ABRIDGEDTRANSFORMATION, GEOGTRAN, COORDINATEOPERATION). /Can you 
> recommend a way to get started with understanding WKT?/ As a 
> geodesist, I am familiar with transformation methods, so I only need 
> information on how to translate between this theory and WKT.
>
> Kind regards, Jochem
>
>
>
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