[PROJ] Need for New CRS's with default datum transformation in PROJ with EPSG 6206 for North Macedonian three CRSs'

Even Rouault even.rouault at spatialys.com
Wed Apr 6 08:54:34 PDT 2022 

Bashkim,

 From some tests, PROJ master with the latest EPSG update (and thus QGIS 
for versions that will use it) should use the EPSG:6206 transformation 
by default for CRS 6204 and 9945. I've also just queued an improvement 
in https://github.com/OSGeo/PROJ/pull/3158 for the generation of PROJ.4 
string for those CRSs, but that should not really impact QGIS use

EPSG:6316 is a more difficult case because this CRS has 2 usages/extents:

     USAGE[
         SCOPE["Cadastre, engineering survey, topographic mapping (large 
and medium scale)."],
         AREA["Bosnia and Herzegovina - east of 19°30'E; Kosovo; 
Montenegro - east of 19°30'E; Serbia - between 19°30'E and 22°30'E."],
         BBOX[41.85,19.5,46.18,22.5]],
     USAGE[
         SCOPE["Cadastre."],
         AREA["North Macedonia."],
         BBOX[40.85,20.45,42.36,23.04]],

PROJ internals (especially the part that "computes" transformation 
pipeline) only use one single usage/extent in part of logics that are 
extent base, and this must be the first one listed, hence not North 
Macedonia. And even if both would be considered, selecting EPSG:6206 as 
a default transformation wouldn't be appropriate for the non-North 
Macedonia usage.

Even

Le 06/04/2022 à 16:48, Bashkim IDRIZI via PROJ a écrit :
>
> Dear All,
>
> First let me to introduce myself. I am Bashkim Idrizi from North 
> Macedonia. Lecturer of cartography and GIS in geodesy department.
>
> Recently on March 18, three changes have been made by our request in 
> EPSG registry database (epsg.org, 2022.009), concerning to CRS of 
> North Macedonia. Based on new updates, there are three CRSs’ for North 
> Macedonian CRS: 6204, 6316 and 9945.
>
> Next step toward elimination of problems with usage of CRS’s for North 
> Macedonian spatial data, is defining single default datum 
> transformation for three CRS’s (6204, 6316 and 9945), based on EPSG 
> 6206 for datum transformation between MGI 1901 and WGS84.
>
> This is very important for GIS users in our country, because at this 
> moment, overlapping with open data such google map etc., is with very 
> very low accuracy.
>
> My request is to create three proj strings as default for upper three 
> mentioned CRS’s, in order to be used by all GIS software users without 
> need for deep knowledge for coordinate systems:
>
> *CRS*
>
> 	
>
> *PROJ STRING *
>
> 	
>
> *Datim transformation EPSG code*
>
> EPSG 6204
>
> 	
>
> +proj=tmerc +lat_0=0 +lon_0=21 +k=0.9999 +x_0=500000 +y_0=0 
> +ellps=bessel 
> +towgs84=521.748,229.489,590.921,4.029,4.488,-15.521,-9.78 +units=m 
> +no_defs
>
> 	
>
> 6206
>
> EPSG
>
> 6316
>
> 	
>
> +proj=tmerc +lat_0=0 +lon_0=21 +k=0.9999 +x_0=7500000 +y_0=0 
> +ellps=bessel 
> +towgs84=521.748,229.489,590.921,4.029,4.488,-15.521,-9.78 +units=m 
> +no_defs
>
> 	
>
> 6206
>
> EPSG
>
> 9945
>
> 	
>
> +proj=tmerc +lat_0=0 +lon_0=21 +k=0.9999 +x_0=500000 +y_0=-4000000 
> +ellps=bessel 
> +towgs84=521.748,229.489,590.921,4.029,4.488,-15.521,-9.78 +units=m 
> +no_defs
>
> 	
>
> 6206
>
> This initiative I started with paper that have been published and 
> presented in ICA conference 2021 
> https://www.proc-int-cartogr-assoc.net/4/45/2021
>
> To be more clear, my intention is to make simple and easier usage of 
> CRS’s by users in North Macedonia in a case when they overlap official 
> data with data coming from other sources based on WGS84 datum.
>
> As example I will mention QGIS software, which use default datum 
> transformation parameters, and in parallel offers “ask” option if 
> several datum transformations are available. Second option can be used 
> by geodetic professionals, however most of GIS users are not able to 
> use this option and they have troubles in overlapping their data in 
> state CRS with global data such openstreetmap, google map, etc.
>
> Therefore I started this initiative to solve this problem step by 
> step. First was creating all EPSG codes for three type of spatial data 
> which was finished in March 18^th , and second is this/todays request 
> to you for defining in PROJ the EPSG 6206 as default datum 
> transformation for three CRS’s (6204, 6316 and 9945), which will 
> enable their usage by all GIS software users without deep knowledge in 
> coordinate systems.
>
> Maybe my explanation was not precise in above text, therefore I will 
> try to give some additional details on this issue. I order to be more 
> clear I will explain with concrete example by QGIS software:
>
>  1. In current version of EPSG 6316, in a case of usage in QGIS with
>     non-checked “ask option if several datum transformations are
>     available”, software doesn’t ask user for selecting of appropriate
>     transformation, and use bellow values as default transformation:
>     +proj=tmerc +lat_0=0 +lon_0=21 +k=0.9999 +x_0=7500000 +y_0=0
>     +ellps=bessel +towgs84=682,-203,480,0,0,0,0 +units=m +no_defs
>  2. More than 90% of users (except geodetic professionals) don’t know
>     what is datum transformation, and they uncheck the “ask option if
>     several datum transformations are available” option (from
>     setting/options/CRS/transformations), or never use if this box is
>     unchecked by installation.
>      1. In this case, QGIS software users in our country works with
>         totally wrong datum transformation, which results with large
>         difference between data in 6316 with global data developed in
>         WGS84.
>  3. In order to avoid such problems, my request is to change those
>     “default” datum transformation parameters
>     (+towgs84=682,-203,480,0,0,0,0) in a case when the box “ask option
>     if several datum transformations are available” is unchecked, with
>     the transformation parameters defined in 6202 (+proj=tmerc
>     +lat_0=0 +lon_0=21 +k=0.9999 +x_0=7500000 +y_0=0 +ellps=bessel
>     *+towgs84=521.748,229.489,590.921,4.029,4.488,-15.521,-9.78*
>     +units=m +no_defs).
>      1. Maybe “default datum transformation” is not appropriate term.
>         Now I hope that my request is more clear.
>  4. I am aware that QGIS will continue to propose all candidate
>     operations reported by PROJ in a case when CRS intersects with
>     several areas in a case when box “ask option if several datum
>     transformations are available” is checked. This is correct and it
>     very important for geodetic experts, that are able to use
>     appropriate transformation in a case of several transformation
>     parameters are available.
>  5. *_Main objective of my request is only in a case when user don’t
>     check/use the box “ask option if several datum transformations are
>     available” and software work with default transformation
>     parameters. _*
>      1. *_In this case, as datum transformation to WGS84 for three
>         CRS’s (EPSG 6316, EPSG 6204, and EPSG 9945) to be set EPSG
>         6206 as primary/default datum transformation from MGI 1901 to
>         WGS84 (see table in my previous email). _*
>
> If the request is not clear, please don’t hesitate to ask me for every 
> detail, as well as I am able to schedule online meeting with you.
>
> Sincerely yours,
>
> Bashkim Idrizi.
>
> ==================================================
>
> *Prof.Dr. Bashkim IDRIZI <https://bashkim-idrizi.blogspot.com/>*
>
> *----------------------------------------------------------------------------------*
>
> University of Prishtina <http://www.uni-pr.edu/>/, Cartography & GIS 
> lecturer/
>
> University "Mother Teresa" Skopje <http://www.unt.edu.mk/>/, 
> Cartography lecturer /
>
> Geo-SEE Institute <http://www.geo-see.org/>/, President /
>
> State University of Tetova <http://www.unite.edu.mk/>/, Past 
> cartography & GIS lecturer /
>
> _Karl Gega Association, <http://www.karl-gega.org/>_/ Past President /
>
> adress: str. Djon Kenedi, 25/4-20; 1010 Skopje, North Macedonia.
>
> gsm-mk: + 389 /75/ 712-998 (Viber & WhatsApp)
>
> gsm-ks: + 383 /45/ 341-098
>
> skype: bashkim.idrizi   (bashkim.idrizi at yahoo.com)
>
> ==================================================
>
>
> _______________________________________________
> PROJ mailing list
> PROJ at lists.osgeo.org
> https://lists.osgeo.org/mailman/listinfo/proj

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