[PROJ] How to write LAS points in N-E CRS

[Javier Jimenez Shaw]

Thank you!
.___ ._ ..._ .. . ._.  .___ .. __ . _. . __..  ... .... ._ .__
Entre dos pensamientos racionales
hay infinitos pensamientos irracionales.



On Mon, 29 Jun 2020 at 16:37, Howard Butler <howard at hobu.co> wrote:

>
>
> > On Jun 29, 2020, at 8:26 AM, Javier Jimenez Shaw <j1 at jimenezshaw.com>
> wrote:
> >
> > Hi
> >
> > I am writing a LAS file using a Northing-Easting CRS (EPSG:2384 for
> instance).
> >
> > I am not sure in which order I should write the point coordinates:
> northing-easting-up or easting-northing-up.
> > * The first option (northing-easting-up) is "consistent" with the
> definition of the CRS. However it needs to understand the axes of the CRS
> (is this only possible in WKT2?), and operate the values to display them on
> the screen. Otherwise you will see a reflected image.
> > * The second option (easting-northing-up) is much easier to represent in
> the screen. And seems to be what many programs are doing/expecting.
> However, it is inconsistent with the CRS definition.
> >
>
> Javier,
>
> Unfortunately there are not many satisfactory answers for you. The 1.4 LAS
> specification is deficient in that it says nothing about allowing any
> future versions of WKT, and it should be assumed that clients are only
> going to be able to consume WKT1:GDAL when writing data. I have attempted
> to start the wheels in motion to spin up the committee for another revision
> of the LAS specification to address this issue [1]. LAS 1.4 is going to be
> especially challenging in situations where orthometric data are written
> into time-dependent coordinates because there will be no way to communicate
> it. With the NGS delaying their rollout in the US, the immediate pressure
> caused by this need may have lessened, however.
>
> I think the pragmatic answer to your question is to chose the latter
> approach, and then deal with the consequences once it is possible to more
> accurately model the axes in WKT2.
>
> Howard
>
> [1] https://github.com/orgs/ASPRSorg/teams/lwg/discussions/16/comments/1
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/proj/attachments/20200629/019a4746/attachment.html>