[Proj] Transformation pipelines - your opinion?

[Howard Butler]

> On Jun 4, 2016, at 10:46 PM, Thomas Knudsen <knudsen.thomas at gmail.com> wrote:
> 
> 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.

This looks like a really great addition! I've been watching the pull request with excitement that this approach will provide more avenues for these kinds of challenging problems. As a point cloud and LiDAR person, these capabilities will be very useful, and the momentum you and Kristian have been building to improve Proj.4 maintenance and feature set is greatly appreciated.

Carry on!

Howard