[PROJ] PROJ7 in JavaScript

[mista_pink at web.de]

Hi everyone,

If you want to Proj support in Node I would suggest looking at native
abstractions (https://github.com/nodejs/nan).
This way the underlying Proj can easily advance and use SQLite etc. It
would "only" need the wrapper/bridges.

This then of course cannot be used in a browser, but there WASM might be
an idea.

Best,
Paul

On 03.10.20 21:16, Lesparre, Jochem wrote:
> At the Dutch NMA, I have had questions on the possibilities to do the
> Dutch transformation including precise datum transformation using the
> horizontal and vertical grid shift files in Java or JavaScript. So, I
> agree with Howard that there would be demand for PROJ in JavaScript.
>
> Regards, Jochem
>
> *From:*PROJ <proj-bounces at lists.osgeo.org> *On Behalf Of *Howard Butler
> *Sent:* zaterdag 3 oktober 2020 15:19
> *To:* Richard Greenwood <richard.greenwood at gmail.com>
> *Cc:* proj <PROJ at lists.osgeo.org>
> *Subject:* Re: [PROJ] PROJ7 in JavaScript
>
>
>
>     On Oct 2, 2020, at 8:21 PM, Richard Greenwood
>     <richard.greenwood at gmail.com <mailto:richard.greenwood at gmail.com>>
>     wrote:
>
>     I am mistaken regarding web assembly support in Node.
>     https://www.joyent.com/blog/improved-wasm-support-coming-to-node
>
> Yes. Emscripten will also degrade to plain JavaScript as well, so that
> is an option for runtimes that can't consume wasm.
>
>
>
>     On Fri, Oct 2, 2020 at 1:43 PM Richard Greenwood
>     <richard.greenwood at gmail.com <mailto:richard.greenwood at gmail.com>>
>     wrote:
>
>         Proj 6 and 7 don't really add any new functionality. Proj does
>         forward in inverse projections and it does datum transformations
>         with 3 & 7 parameters transforms and grid shift transforms.
>         Proj4js supports most of the commonly used projections and the 3
>         & 4 param datum transforms.
>
> Proj4js doesn't support WKTv2 consumption or emission, and it doesn't
> support PROJJSON [1].  At the very least, interoperability suffers when
> crossing the proj4js boundary when trying to communicate coordinate
> system descriptions.
>
>
>
>         It doesn't support grid shift transforms and grid shift
>         transforms are what are "heavy" in terms of the size of the
>         required data. I thought a lot about adding grid shift support
>         and considered a server-side option like Javier mentions, but
>         it's a lot of moving parts for pretty limited use cases. Like
>         how many web mapping apps need the precision of a grid shift
>         transform? And for those that do, how do you build a generic
>         enough mechanism to cover the variations in scale, platform,
>         online/offline, etc.?
>
> I think the combination of COGs at cdn.proj.org
> <http://cdn.proj.org> and geotiff.js would allow for the construction of
> JavaScript support for high performance incremental grid access similar
> to the current PROJ runtime's incremental implementation. There would be
> no need to cache GBs of grid files, and the data is hosted today as web
> native as you can get as COGs in CloudFront.
>
> I think it is a mistake to see JavaScript support as only "web mapping
> apps". I think a WASM port of PROJ is a worthy goal for a number of
> reasons, but the community has to want it bad enough to invest to make
> it happen. To date, that hasn't been demonstrated.
>
> Howard
>
> [1] https://proj.org/specifications/projjson.html
>
>
>
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