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

Thu Apr 7 10:47:32 PDT 2022

Dear Even, 

Thanks for your quick response. Very fruitful assistance! 

Concerning to EPSG 6316, as I understood, the only way is to create new-separate CRS for North Macedonia with same parameters of 6316, in order to solve our problem. This means that we should go back to EPSG with new request for new CRS! 

Do you have any other idea? 

Thanks in advance. 

Bashkim. 

From: Even Rouault <even.rouault at spatialys.com> 
Sent: Wednesday, April 6, 2022 5:55 PM
To: Bashkim IDRIZI <bashkim.idrizi at yahoo.com>; proj at lists.osgeo.org
Subject: Re: [PROJ] Need for New CRS's with default datum transformation in PROJ with EPSG 6206 for North Macedonian three CRSs'

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 18th, 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. 

==================================================

 <https://bashkim-idrizi.blogspot.com/> Prof.Dr. Bashkim IDRIZI

----------------------------------------------------------------------------------

 <http://www.uni-pr.edu/> University of Prishtina, Cartography & GIS lecturer 

 <http://www.unt.edu.mk/> University "Mother Teresa" Skopje, Cartography lecturer 

 <http://www.geo-see.org/> Geo-SEE Institute, President   

 <http://www.unite.edu.mk/> State University of Tetova, Past cartography & GIS lecturer 

 <http://www.karl-gega.org/> Karl Gega Association, 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 <mailto:bashkim.idrizi at yahoo.com> )

==================================================

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