[PROJ] Latitude of natural origin in Transverse Mercator

[Paul Harwood]

Whilst I have nothing like the mathematical knowledge or expertise of those
who have already answered, I have some experience of playing around with
this for an app that puts geographic entities into a VR space that needs
locally accurate cartesian coordinates using an engineering projection that
is TM with a local, arbitrary origin.

I would totally agree with Janne. If you want to avoid confusing yourself
and everyone around you and making hard-to-diagnose bugs - keep the input
coords of the origin in the input CRS.

Just thinking about the BNG case, although the False Northing is
mathematically the same as the Latitude of origin, the False Easting is not
the same the Central Longitude (since I would understand that the former is
already projected) and you would need to clearly understand if the units of
the False Northing are subject to the local scaling factors. All totally
mathematically possible, of course, but from a design, coding and
especially from a maintenance perspective a total nightmare.

Paul

On Sat, 14 Jan 2023 at 13:35, <support at mnspoint.com> wrote:

> Hello,
>
> You have angular latitudes on the globe and eastings and northings on
> the resulting map plane. One should not mix them to stay out of trouble.
>
> Janne.
>
> -----------------------------------------------
> Javier Jimenez Shaw kirjoitti 2023-01-13 16:28:
> > Hi
> >
> > I have a question about Transverse Mercator.
> > What is the impact of the parameter "Latitude of natural origin",
> > compared with the "False Northing"? (apart from the fact that one is
> > in degrees and the other in meters)
> >
> > Is there any difference on using a Latitude of natural origin of,
> > let's say, 40 degrees, or compute the equivalent False Northing?
> >
> _______________________________________________
> PROJ mailing list
> PROJ at lists.osgeo.org
> https://lists.osgeo.org/mailman/listinfo/proj
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/proj/attachments/20230121/a49e0a8c/attachment.htm>