[pdal] reader plugin for Leica PTX

[Howard Butler]

> On Mar 17, 2022, at 12:13 PM, Jed Frechette <jedfrechette at gmail.com> wrote:
> 
> On  Thu, 17 Mar 2022 08:38:00 +0000 Daniel Brookes
> <dbrookes at micromine.com> wrote
>> Curious if there is any interest in supporting Leica PTX files in pdal.
> 
> PTX files are still used pretty commonly by people working with tripod
> scanner data so I think supporting them does offer some value.
> 
> That being said, the main reason for a user to choose PTX over PTS
> would be to store structured data and to preserve scan level
> transforms. Therefore, as a user, a PTX reader that simply converts
> the scan to an unstructured point cloud and bakes in the transform is
> much less useful than one that preserves that information. Pretty much
> any software that supports exporting PTX will also support exporting
> PTS, since they were basically intended as the structured and
> unstructured variants of an ascii exchange format.

I could see how it would be useful for data formats with transforms built-in to push that information into stage metadata in a common way such that filters and writers can pick them up and use them. That could be obvious uses like filters.transformation. Multiplexing of transforms and positions from something like a single E57 file would seem out of scope for PDAL pipelines themselves, however.

> 
> e57 has a similar dichotomy, even though in that case you can store
> either structured or unstructured data inside the same file. One core
> PDAL feature that would make both PTX and e57 support a lot more
> useful for structured data would be to simply add rowIndex and
> columnIndex dimensions.

Please make a PR to implement these. 

> As a user being able to load structured data
> into PDAL, do some stuff to it, then save out structured data would be
> really useful. Even if PDAL filters continue to only operate on
> unstructured data and simply pass through the array indexes so that
> the arrays can be reassembled by the writers that would open up a lot
> of potential workflows.

As always, pull requests or funding can make these desires happen.