[Proj] Differences across v4.8 and v4.9

[Joaquim Luis]

Thanks Kristian,

The differences in A1/B1 are, like Even found, due to missing grids in the  
nad directory.

Regarding this and the others, I'm implementing proj.4 in GMT and so want  
to be sure that the discrepancies that I find meanwhile are not due to  
errors of mine.

Joaquim


> Hi Joaquin,
>
> For specifics about changes between versions you should consult the NEWS  
> file in the source distribution [0],
> or even better, the git commit log [1].
>
> I tried recreating your findings with the following script:
>
> -----------------------------------------------------------------------------------------------------------------------------------------------
> #!/bin/sh
>
> proj
>
> echo A1
> echo 45.25919444444 -111.5 | cs2cs +proj=latlong +datum=NAD83 +to  
> +proj=utm +zone=10  +datum=NAD27 -r
> echo "1402285.99      5076292.42 -0.00"
> echo
> echo A2
> echo 4.897 52.371 | proj +proj=aeqd +ellps=WGS84 +units=m
> echo "384923.72       5809986.50"
> echo
> echo A3
> echo 4.897 52.371 | proj +proj=robin +ellps=WGS84 +units=m
> echo "394576.51       5571243.64"
> -----------------------------------------------------------------------------------------------------------------------------------------------
>
> And got the following output:
>
> -----------------------------------------------------------------------------------------------------------------------------------------------
> $ ./test_proj4.9.3.sh
> Rel. 4.9.3, 15 August 2016
> usage: proj [ -bCeEfiIlormsStTvVwW [args] ] [ +opts[=arg] ] [ files ]
> A1
> 1402285.98	5076292.42 -0.00
> 1402285.99      5076292.42 -0.00
>
> A2
> 384537.46	5809944.81
> 384923.72       5809986.50
>
> A3
> 394576.53	5570940.84
> 394576.51       5571243.64
> -----------------------------------------------------------------------------------------------------------------------------------------------
>
> So, I am not able to reproduce the output you get in B1, although I do  
> get an answer very similar to A1.
> This discrepancy can most likely be explained by the fact that the  
> default UTM implementation was changed
> to etmerc with version 4.9.3.
>
> For the second example I get the same difference as you. I believe this  
> can be explained by the improved
> geodesic code that was introduced 4.9.0. The aeqd code was updated when  
> GeographicLib [2].
>
> Your third example I can also recreate. I believe it might be caused by  
> a change in coefficients in the
> source code [3].
>
> For all of the three examples you've found, I would say that the reason  
> for them is that the algorithms
> have been improved (although documented poorly). The examples in the doc  
> pages should obviously be
> updated to reflect the current behaviour of PROJ.4.
>
> /Kristian
>
> [0] https://github.com/OSGeo/proj.4/blob/master/NEWS
> [1] https://github.com/OSGeo/proj.4/commits/master
> [2]  
> https://github.com/OSGeo/proj.4/commit/de8d6779aaabe0c46c06b9047bc6a6a978cc0758
> [3]  
> https://github.com/OSGeo/proj.4/commit/d856016ca1a178cc81c4474c0a6bbe78d106d012
>
> ________________________________________
> Fra: proj-bounces at lists.maptools.org [proj-bounces at lists.maptools.org]  
> på vegne af Joaquim Luis [jmfluis at gmail.com]
> Sendt: 28. august 2017 18:46
> Til: PROJ.4 and general Projections Discussions
> Emne: [Proj] Differences across v4.8 and v4.9
>
> Hi,
>
> I have found these differences between proj.4 versions that I don't find
> any documentation referring them. There is one FAQ
> http://proj4.org/faq.html#why-do-i-get-different-results-with-4-5-0-and-4-6-0
> entry but is about differences between 4.5.0 and 4.6.0, whilst this is
> between 4.8 and 4.9.
>
> The first one (between A1 and B1) is specially more troublesome because  
> is
> the example provide in the cs2cs doc page
> (http://proj4.org/apps/cs2cs.html) that agrees with 4.8.0 and not with
> 4.9.2
>
> Joaquim
>
> proj
> Rel. 4.8.0, 6 March 2012
>
> A1
> echo 45.25919444444 -111.5 | cs2cs +proj=latlong +datum=NAD83 +to
> +proj=utm +zone=10  +datum=NAD27 -r
> 1402285.99      5076292.42 -0.00
>
> A2
> echo 4.897 52.371 | proj +proj=aeqd +ellps=WGS84 +units=m
> 384923.72       5809986.50
>
> A3
> echo 4.897 52.371 | proj +proj=robin +ellps=WGS84 +units=m
> 394576.51       5571243.64
>
> -------------------------------------------------------------------------------
> proj
> Rel. 4.9.3, dd Month yyyy
>
> B1
> echo 45.25919444444 -111.5 | cs2cs +proj=latlong +datum=NAD83 +to
> +proj=utm +zone=10  +datum=NAD27 -r
> 1402292.27      5076292.65 -0.00
>
> B2
> echo 4.897 52.371 | proj +proj=aeqd +ellps=WGS84 +units=m
> 384537.46       5809944.81
>
> B3
> echo 4.897 52.371 | proj +proj=robin +ellps=WGS84 +units=m
> 394576.53       5570940.84
> _______________________________________________
> Proj mailing list
> Proj at lists.maptools.org
> http://lists.maptools.org/mailman/listinfo/proj
> _______________________________________________
> Proj mailing list
> Proj at lists.maptools.org
> http://lists.maptools.org/mailman/listinfo/proj