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Add towgs84 parameters to some CRS for Portugal #17618
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Author Name: Giovanni Manghi (@gioman) EPSG 27493/20790 use those parameters.
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Author Name: Antonio Sobral Almeida (Antonio Sobral Almeida) Hello Giovanni
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Author Name: Giovanni Manghi (@gioman) Antonio Sobral Almeida wrote:
Hi Antonio, Just to let me understand better: I remember that ESRI sofware was not saving vectors with towgs84 parameters in their Portuguese CRSs definitions (102160/1/4/5). Are you saying that they do now? If the answer is "yes" then you may want to consider that if the QGIS definitions will be updated, then all old the vectors that were been given the definitions without the towgs84 parameters will be given (on load) by QGIS an internal code (it starts from 100000), so then there will be a lot of people complaining that their shapes are given a "strange" CRS. Meanwhile you may want to consider manually giving to your vectors the 20790/27493 and then saving copies in the same CRS. Feel free to contact me privately: giovanni.manghi@faunalia.pt |
Author Name: Antonio Sobral Almeida (Antonio Sobral Almeida) Hello Giovanni, No, ESRI projection files do not have ToWGS84 parameters. This and the fact that the above mentioned ESRI-based projection files are widely used in Portugal, makes any migration intention to QGis rather improbable, due to the reasons stated above. |
Author Name: Giovanni Manghi (@gioman) Antonio Sobral Almeida wrote:
Hi Antonio, I would not say that migrating to QGIS in Portugal is "rather improbable", considered the many (many) persons and entities that have happily migrated. The issue you are raising is easily solved, I just lack the time to answer extensively right now. It is possible that things can be improved but certainly is not a blocker issue. Write to you soon. |
Author Name: Antonio Sobral Almeida (Antonio Sobral Almeida) Hi Giovanni,
That is a VERY GOOD reason for QGis developers to correct this bug! Regards |
Author Name: Giovanni Manghi (@gioman)
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Author Name: Giovanni Manghi (@gioman) Antonio Sobral Almeida wrote:
Dear Antonio, the suggestion to add the towgs84 parameters to the ESRI CRSs makes sense, anyway this cannot be seen strictly as a bug. Until the CRS will be modified you can easily workaround the problem in many ways: +) when adding the vectors manualy change their CRS to the equivalent EPSG code (20790/20791/27493) +) remove the .prj/qpj files of your layers and configure qgis (in the general options) to give them (on load) a specific CRS (20790/20791/27493) +) create copies of your layers giving them the EPSG CRSs (20790/20791/27493): it is not necessary to make this operation one by one, you can batch process your layers using the processing toolbox (aka Sextante) and the tools "reproject layer" (for vectors) and "warp" (for rasters). |
Author Name: Giovanni Manghi (@gioman)
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Author Name: Nyall Dawson (@nyalldawson) With QGIS 3.8 and the release of proj 6 library, any remaining projection definition related issues now should be filed with the proj project.
introduction: The CRSs with code 102160/102161/102164/102165 (originally from ESRI) are widely used in Portugal (even if now superseded by 3763). 102161 is identical to EPSG 27493 102164/102165 are the same as EPSG 20790/20791 even if the definitions is slightly different. 102160 does not seems to have an equivalent EPSG CRS. 27493/20790/20791 are shipped in QGIS with TOWGS84 parameters, this is very good because they allow to transform/reproject layers with a much needed precision. The suggestion is to modify the 102160/102161/102164/102165 CRSs by adding the very same TOWGS84 parameters: for 102160/1 +towgs84=-223.237,110.193,36.649,0,0,0,0 and for 102164/102165 +towgs84=-304.046,-60.576,103.64,0,0,0,0 Old Description: The following ESRI-based CRSs are lacking DATUM transformation parameters (ToWGS84): The trnasformation parameters for these CRSs can be found, for example, in ArcPAD 7 system files, as the one attached. to New description: introduction: The CRSs with code 102160/102161/102164/102165 (originally from ESRI) are widely used in Portugal (even if now superseded by 3763). 102161 is identical to EPSG 27493 102164/102165 are the same as EPSG 20790/20791 even if the definitions is slightly different. 102160 does not seems to have an equivalent EPSG CRS. 27493/20790/20791 are shipped in QGIS with TOWGS84 parameters, this is very good because they allow to transform/reproject layers with a much needed precision. The suggestion is to modify the 102160/102161/102164/102165 CRSs by adding the very same TOWGS84 parameters: for 102160/1 +towgs84=-223.237,110.193,36.649,0,0,0,0 and for 102164/102165 +towgs84=-304.046,-60.576,103.64,0,0,0,0 Old Description: The following ESRI-based CRSs are lacking DATUM transformation parameters (ToWGS84): The trnasformation parameters for these CRSs can be found, for example, in ArcPAD 7 system files, as the one attached. |
Author Name: Antonio Sobral Almeida (Antonio Sobral Almeida)
Original Redmine Issue: 8954
Redmine category:projection_support
New description:
introduction:
The CRSs with code 102160/102161/102164/102165 (originally from ESRI) are widely used in Portugal (even if now superseded by 3763).
102161 is identical to EPSG 27493
102164/102165 are the same as EPSG 20790/20791 even if the definitions is slightly different.
102160 does not seems to have an equivalent EPSG CRS.
27493/20790/20791 are shipped in QGIS with TOWGS84 parameters, this is very good because they allow to transform/reproject layers with a much needed precision.
The suggestion is to modify the 102160/102161/102164/102165 CRSs by adding the very same TOWGS84 parameters:
for 102160/1
+towgs84=-223.237,110.193,36.649,0,0,0,0
and for 102164/102165
+towgs84=-304.046,-60.576,103.64,0,0,0,0
Old Description:
The following ESRI-based CRSs are lacking DATUM transformation parameters (ToWGS84):
Lisboa_Hayford_Gauss_IGeoE
Lisboa_Hayford_Gauss_IPCC
Datum_73_Hayford_Gauss_IGeoE
Datum_73_Hayford_Gauss_IPCC
The trnasformation parameters for these CRSs can be found, for example, in ArcPAD 7 system files, as the one attached.
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