Unneccessarily inaccurate transformation Gauß-Krüger to UTM

[qgib]

Author Name: Rudi Uhl (@RudiU)
Original Redmine Issue: 11347

Redmine category:projection_support

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Hello,

Some months ago I reported what I believed to be a bug in transforming East German Krassovski coordinates to other projections like UTM. I was tought that due to limitations in Proj.4 there is only one transformation for each EPSG code, so there is no choice of transformation. Compared to ArcGIS that's a serious disadvantage. It can easily be overcome by the knowable, in case of the east German transformation you just have to edit the +towgs part (change to +towgs84=24,-123,-94,0.02,-0.25,-0.13,1.1).

However I doubt that it makes sense to get users into trouble like that if it can easily be prevented. There is a long-standing precise official transformation for Gauß-Krüger (Bessel) to UTM in Germany called Beta2007, but for reasons I don't (want to) understand it's not delivered with the QGIS package so far. We are in Germany in the middle of a process switching from Gauß-Krüger to UTM. But every time users use QGIS to reproject data they introduce shifts of up to 3 meters (indeed quite exactly 3 meters in the southwest of Germany). For my part, I can't use QGIS if I have to be afraid that the data I deliver have to be considered as faulty, if I (or others) need sub-meter precision.

Meanwhile I found the solution, which should be delivered as default:

1. Download BETA2007.gsb, official site: http://crs.bkg.bund.de/crseu/crs/descrtrans/BeTA/BETA2007.gsb
2. Save it to the \share\proj
3. Add custom CRSs (On the long run they should replace the existing EPSG declarations):

    Name: GK2 DHDN / Bessel (Beta2007) EPSG 31466
    Parameter: +proj=tmerc +lat_0=0 +lon_0=6 +k=1 +x_0=2500000 +y_0=0 +ellps=bessel  +units=m +nadgrids=BETA2007.gsb +no_defs
    Name: GK3 DHDN / Bessel (Beta2007) EPSG 31467
    Parameter: +proj=tmerc +lat_0=0 +lon_0=9 +k=1 +x_0=3500000 +y_0=0 +ellps=bessel  +units=m +nadgrids=BETA2007.gsb +no_defs
    Name: GK3 DHDN / Bessel (Beta2007) EPSG 31468
    Parameter: +proj=tmerc +lat_0=0 +lon_0=12 +k=1 +x_0=4500000 +y_0=0 +ellps=bessel  +units=m +nadgrids=BETA2007.gsb +no_defs

I think QGIS is a great achievement, and I'm grateful to everybody who takes part in the concerted efforts of developing it. It would be a pity if its usefulness is severly limited by such an issue.

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Related issue(s): #22547 (duplicates)
Redmine related issue(s): 14574

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[qgib]

Author Name: Jürgen Fischer (@jef-n)

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The grid references were meanwhile added, but the grid itself is not included. It's still unclear whether it's ok to redistribute the grid.

[qgib]

Author Name: Jürgen Fischer (@jef-n)

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I contacted Uwe (contact of the "grid":http://crs.bkg.bund.de/crseu/crs/descrtrans/BeTA/de_dhdn2etrs_beta.php) about the it's licensing.

[qgib]

Author Name: Jürgen Fischer (@jef-n)

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Pull Request "PROJ.4 !#10430":OSGeo/PROJ#371 to add BETA2007.gsb to proj.4 submitted

[qgib]

Author Name: Jürgen Fischer (@jef-n)

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@proj-beta2007@ package added to osgeo4w

[qgib]

Author Name: Giovanni Manghi (@gioman)

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• easy_fix was configured as 0

[qgib]

Author Name: Nyall Dawson (@nyalldawson)

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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.

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• resolution was changed from to up/downstream
• description was changed from Hello,

Some months ago I reported what I believed to be a bug in transforming East German Krassovski coordinates to other projections like UTM. I was tought that due to limitations in Proj.4 there is only one transformation for each EPSG code, so there is no choice of transformation. Compared to ArcGIS that's a serious disadvantage. It can easily be overcome by the knowable, in case of the east German transformation you just have to edit the +towgs part (change to +towgs84=24,-123,-94,0.02,-0.25,-0.13,1.1).

However I doubt that it makes sense to get users into trouble like that if it can easily be prevented. There is a long-standing precise official transformation for Gauß-Krüger (Bessel) to UTM in Germany called Beta2007, but for reasons I don't (want to) understand it's not delivered with the QGIS package so far. We are in Germany in the middle of a process switching from Gauß-Krüger to UTM. But every time users use QGIS to reproject data they introduce shifts of up to 3 meters (indeed quite exactly 3 meters in the southwest of Germany). For my part, I can't use QGIS if I have to be afraid that the data I deliver have to be considered as faulty, if I (or others) need sub-meter precision.

Meanwhile I found the solution, which should be delivered as default:

Download BETA2007.gsb, official site: http://crs.bkg.bund.de/crseu/crs/descrtrans/BeTA/BETA2007.gsb

Save it to the \share\proj

Add custom CRSs (On the long run they should replace the existing EPSG declarations):

    Name: GK2 DHDN / Bessel (Beta2007) EPSG 31466
    Parameter: +proj=tmerc +lat_0=0 +lon_0=6 +k=1 +x_0=2500000 +y_0=0 +ellps=bessel  +units=m +nadgrids=BETA2007.gsb +no_defs
    Name: GK3 DHDN / Bessel (Beta2007) EPSG 31467
    Parameter: +proj=tmerc +lat_0=0 +lon_0=9 +k=1 +x_0=3500000 +y_0=0 +ellps=bessel  +units=m +nadgrids=BETA2007.gsb +no_defs
    Name: GK3 DHDN / Bessel (Beta2007) EPSG 31468
    Parameter: +proj=tmerc +lat_0=0 +lon_0=12 +k=1 +x_0=4500000 +y_0=0 +ellps=bessel  +units=m +nadgrids=BETA2007.gsb +no_defs

I think QGIS is a great achievement, and I'm grateful to everybody who takes part in the concerted efforts of developing it. It would be a pity if its usefulness is severly limited by such an issue. to Hello,

Some months ago I reported what I believed to be a bug in transforming East German Krassovski coordinates to other projections like UTM. I was tought that due to limitations in Proj.4 there is only one transformation for each EPSG code, so there is no choice of transformation. Compared to ArcGIS that's a serious disadvantage. It can easily be overcome by the knowable, in case of the east German transformation you just have to edit the +towgs part (change to +towgs84=24,-123,-94,0.02,-0.25,-0.13,1.1).

However I doubt that it makes sense to get users into trouble like that if it can easily be prevented. There is a long-standing precise official transformation for Gauß-Krüger (Bessel) to UTM in Germany called Beta2007, but for reasons I don't (want to) understand it's not delivered with the QGIS package so far. We are in Germany in the middle of a process switching from Gauß-Krüger to UTM. But every time users use QGIS to reproject data they introduce shifts of up to 3 meters (indeed quite exactly 3 meters in the southwest of Germany). For my part, I can't use QGIS if I have to be afraid that the data I deliver have to be considered as faulty, if I (or others) need sub-meter precision.

Meanwhile I found the solution, which should be delivered as default:

Download BETA2007.gsb, official site: http://crs.bkg.bund.de/crseu/crs/descrtrans/BeTA/BETA2007.gsb

Save it to the \share\proj

Add custom CRSs (On the long run they should replace the existing EPSG declarations):

    Name: GK2 DHDN / Bessel (Beta2007) EPSG 31466
    Parameter: +proj=tmerc +lat_0=0 +lon_0=6 +k=1 +x_0=2500000 +y_0=0 +ellps=bessel  +units=m +nadgrids=BETA2007.gsb +no_defs
    Name: GK3 DHDN / Bessel (Beta2007) EPSG 31467
    Parameter: +proj=tmerc +lat_0=0 +lon_0=9 +k=1 +x_0=3500000 +y_0=0 +ellps=bessel  +units=m +nadgrids=BETA2007.gsb +no_defs
    Name: GK3 DHDN / Bessel (Beta2007) EPSG 31468
    Parameter: +proj=tmerc +lat_0=0 +lon_0=12 +k=1 +x_0=4500000 +y_0=0 +ellps=bessel  +units=m +nadgrids=BETA2007.gsb +no_defs

I think QGIS is a great achievement, and I'm grateful to everybody who takes part in the concerted efforts of developing it. It would be a pity if its usefulness is severly limited by such an issue.

• status_id was changed from Open to Closed