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Is there a way to create a custom geographic transformation with specifics parameters in QGIS like in ArcGIS?

Okay, I want to tranform SAD69 system into WGS84. Well, I'm in doubt because in ArcGIS you have to enter both systems and then specify the method of the transformation - wich is the Molodensky method - and its three parameters - defined by the brazilian government. 

a1 = 6.378.160 m
f1 = 1/298,25
a2 = 6.378.137 m
f2 = 1/298,257222101 ΔX = − 67,35 m
ΔY = + 3,88 m
ΔZ = − 38,22 m

Thanks in advance,

underdark
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Daniel Montenegro
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1 Answers1

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Yes, it's possible to create custom coordinate reference systems (CRSs) in QGIS. Settings -> Custom CRS...

What parameters do you have?

Added later: Is this SAD69 lat/lon? You could try a custom CRS made with this parameter string:

+proj=longlat +ellps=aust_SA +towgs84=-67.35,3.88,-38.22,0,0,0,0 +no_defs

See here How to define new custom projections in QGIS?

Community
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nhopton
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  • Okay, I want to tranform SAD69 system into WGS84. Well, I'm in doubt because in ArcGIS you have to enter both systems and then specify the method of the transformation - wich is the Molodensky method - and its three parameters - defined by the brazilian government. a1 = 6.378.160 m f1 = 1/298,25 a2 = 6.378.137 m f2 = 1/298,257222101 ΔX = − 67,35 m ΔY = + 3,88 m ΔZ = − 38,22 m – Daniel Montenegro Jul 15 '12 at 16:24
  • I've added a suggestion to my answer above. Nick. – nhopton Jul 15 '12 at 18:15
  • No, actually SAD69 is projected (X/Y)! – Daniel Montenegro Jul 15 '12 at 21:23
  • Some are geographic and some are projected. See http://spatialreference.org/ref/?search=SAD69 – nhopton Jul 16 '12 at 07:17
  • Could you please explain how I enter the parameter string in the CRS window? – Daniel Montenegro Jul 16 '12 at 16:36