[Proj] Transformation pipelines - your opinion?

[Thomas Knudsen]

All,

I have recently opened a new pull request over at
https://github.com/OSGeo/proj.4/pull/388 ...

It introduces projection pipelines (i.e. multi-step transformations),
and, at the end-user facing side of things, a new 3D transformation
program called “tran”, which directly supports transformation
pipelines.

While the pull request expands the capabilities of proj.4
dramatically, the code is not very intrusive: Technically, the
pipeline driver is just a new projection, and hence a transformation
pipeline is introduced with the incantation “+proj=pipeline”.

I agree that at first, this may seem a bit odd, so I hope to initiate
a discussion here about e.g. the syntax, and aboult potentially useful
pipeline primitives: The code is still in its infancy, so a lot will
happen before it is ready for merging into the proj.4 master branch
(although I hope it can be done in time for version 4.10)

You can contribute to the discussion here and/or over at the github
page already mentioned. Also, you can read more about syntactic
details at my proj.4 page http://thomasknudsen.net/proj4.html, where
you can also find instructions for downloading a recent Windows build
of the “tran” tool.

/thomas