[Proj] PROJ 5.0.0RC6
Kristian Evers
kreve at sdfe.dk
Wed Feb 28 03:58:15 EST 2018
Hi Matthias,
I just tried reproducing your problem:
echo 12 50 306 0 | cct.exe +proj=pipeline +step +inv +proj=lonlat +datum=WGS84 +ellps=WGS84 +step +proj=utm +zone=33 | cct.exe +proj=pipeline +step +inv +proj=utm +zone=33 +step +proj=lonlat +datum=WGS84 +ellps=WGS84
12.0000000005 49.9999999996 306.0000 0.0000
Without any luck. This is on Windows, so I am not sure what is causing your problem.
Really though, what you are trying to do is not really recommended. Instead of writing a long explanation, I'll just link to what
Thomas wrote the other day about using cs2cs modifiers such as +datum in pipelines:
http://lists.maptools.org/pipermail/proj/2018-February/008055.html
TL;DR: Don't do that, unless invoked from a init-file.
In your specific case there's a much simpler solution:
+proj=utm +zone=33
The reason being that "+proj=lonlat +datum=WGS84 +ellps=WGS84" in the context of pipelines is just a no operation that
passes through whatever comes in unchanged. See for yourself:
λ echo 12 55 0 0|cct.exe +proj=lonlat +datum=WGS84 +ellps=WGS84
12.0000000000 55.0000000000 0.0000 0.0000
Hope that clears things up a bit.
/Kristian
PS. You don't need +ellps=WGS84 when setting +datum=WGS84
-----Oprindelig meddelelse-----
Fra: proj-bounces at lists.maptools.org [mailto:proj-bounces at lists.maptools.org] På vegne af Matthias Gabriel
Sendt: 28. februar 2018 09:13
Til: proj at lists.maptools.org
Emne: Re: [Proj] PROJ 5.0.0RC6
Hi,
I still have a problem using proj4 RC6 on Windows... I try to calculate
the "round-trip" from WGS84 -> UTM -> WGS84 using the following two
pipelines in a unit-test:
+proj=pipeline +step +inv
+proj=lonlat +datum=WGS84 +ellps=WGS84
+step
+proj=utm +zone=33
and its inverse:
+proj=pipeline +step +inv
+proj=utm +zone=33
+step
+proj=lonlat +datum=WGS84 +ellps=WGS84
My test-values are 12.0° 50.0° 306m - of course they are converted into
radians before. I apply the first projection, get an intermediate (UTM)
result and then immediately apply the second pipeline and get again
lonlat in WGS84. Then I compare both WGS84.
On Linux x64 and aarch64 that unit-test succeeds and the result of
applying both pipelines is again 12° and 50°. On Windows VS 15 2017
amd64 its not the case. It seems that the second a application of the
pipeline has no effect, the PJ_COORD still contains the UTM coordinates.
Not even an error is raised (proj_errno equals 0 for the projection ptr)
and of course my unittest fails.
I'm not an expert on projections but as this test succeeds on linux I
find it rather strange...
Regards,
Matthias
On 27/02/18 16:49, Bas Couwenberg wrote:
> On 2018-02-27 15:11, Greg Troxel wrote:
>> Kristian Evers <kreve at sdfe.dk> writes:
>>
>>> Thanks for you feedback, Greg. It is very appreciated.
>>>
>>> I think Bas has commented on most issues already so I'll skip that. I
>>> have updated
>>> the NEWS and README files to take your comments into account:
>>>
>>> https://github.com/OSGeo/proj.4/pull/828
>>>
>>> Let me know if I've missed something or described things in an unclear
>>> way.
>> Thanks - that almost entirely addresses things.
>>
>>
>> A further comment, and I don't mean to suggest that the release be held
>> up:
>>
>> The text talks about how the regional ones are not essential but could
>> be useful. That seems fair. But, as a user, how do I find out what is
>> in them, or what I need, other than by downloading them and inspecting
>> them?
> Use the source, Luke. :-)
>
> https://github.com/OSGeo/proj-datumgrid
>
> Specific subdirectories for the regional packages:
>
> https://github.com/OSGeo/proj-datumgrid/tree/master/europe
> https://github.com/OSGeo/proj-datumgrid/tree/master/north-america
> https://github.com/OSGeo/proj-datumgrid/tree/master/oceania
>
>> As a packager, what should I do? For now, I will include the main file
>> in the package, following tradition, and not worry about the new ones.
>> I am guessing that this means the grids for the important datums are
>> still in the main file, even if they are a North American Datum, and
>> the
>> north-america file contains only more obscure datums that were not
>> previously available. I originally had the impression that all North
>> American grids were demoted from the main file to the regional file.
> proj-datumgrid-north-america includes grids for Greenland.
>
> The "old" NAD grids for North America are still included in the core
> proj-datumgrid package as they have been since pretty much forever.
>
> The filename and content of the proj-datumgrid was explicitly kept the
> same to not require any changes from packagers other than the version
> number.
>
> That is also why the .zip format was kept, and in addition a .tar.gz is
> available as well.
>
>> I updated my draft 5.0.0 package to use proj-datumgrids-1.7RC2, and I
>> see that this added two files compared to 1.5 (which I should have
>> updated but didn't), and did not withdraw any.
>>
>> So I have convinced myself that using the main file for the package,
>> and
>> deferring thinking about the new files is a good approach.
>>
>>
>> So it might help to add
>>
>> All grids that were in proj-datumgrids-1.6 remain in
>> proj-datumgrids-1.7; the regional datumgrid files contain grids for
>> datums not previously supported.
> Where do you suggest to add this?
>
> Kind Regards,
>
> Bas
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--
M.Sc. Matthias Gabriel
Fakultät für Elektrotechnik und Informationstechnik
Technische Universität Chemnitz
Reichenhainer Straße 70 | R. W440
09126 Chemnitz
Germany
Tel: +49 371 531-34458
Fax: +49 371 531-834458
matthias.gabriel at etit.tu-chemnitz.de
www.tu-chemnitz.de
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