[PROJ] Syntax to change projection from UTM to TM

[Javier Jimenez Shaw]

On Sat, 7 Dec 2024, 01:10 Ulises Ibarra via PROJ, <proj at lists.osgeo.org>
wrote:

>
> El vie, 6 dic 2024 a las 17:59, Greg Troxel via PROJ (<
> proj at lists.osgeo.org>) escribió:
>
>> Ulises Ibarra via PROJ <proj at lists.osgeo.org> writes:
>>
>> > echo 480037.249 2143783.696 2271.294 | cct +proj=pipeline +step +inv
>> > +proj=utm +zone=14 +ellps=GRS80 +k=0.9996439573 +step +proj=tmerc
>> > +lat_0=19.388187333 +lon_0=-99.190762728 +x_0=479969.231
>> +y_0=2143791.499
>> > +ellps=GRS80 +k=1
>>
>> I am far from an expert here, but "UTM zone 14" defines everything about
>> the projection, so I don't understand why you are needing to specify the
>> k.  Also sort of the ellipse, but people use UTM with both NAD83 and
>> WGS84, and you are using it with ITRF2008.
>>
>
> * I need to specify in detail because I think I have no idea what I'm
> doing :P
>
If you explain all the inputs in detail, including those k and why you
expect that output, I can try to guess it.
The PROJ pipeline I think is correct, except for the values themselves (k,
false easting and northing)

> .
> * So I understand that the k is not necessary to use in the command. Is
> this correct?
> * I don't understand what you said about there being people who use both
> NAD83 and WGS84 and I am using  ITRF2008, could you explain it better?
> Maybe I shouldn't specify the ellipsoid?
>
>>
>> https://www.oc.nps.edu/oc2902w/maps/utmups.pdf
>>
>> may be useful
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