Opened 13 years ago

Last modified 13 years ago

#3788 new bug

Problem Datum Transformation

Reported by: ImPreZa Owned by: nobody
Priority: major: does not work as expected Milestone: Version 1.7.0
Component: Projection Support Version: 1.6.0
Keywords: datum transformation SAD69 SIRGAS2000 problem displacement shift brazilian ntv2 Cc:
Must Fix for Release: No Platform: Windows
Platform Version: Win7 Awaiting user input: no

Description (last modified by jef)

Hey!!

I've tried to transform a shapefile from EPGS:4618 (SAD69) to EPGS:4674 (SIRGAS2000), but the product of this transformation doesn't shifts. It seems that QGIS export a shapefile with the new projection, but it is unable to apply (in fact) the values of the new ellipsoid.

Here are the official parameters for transformation between the both datums:

DX = -67,35
DY = +3,88
DZ = -38,22

Unfortunately, I couldn't upload the .gsb files (NTV2 transformation, 800kb) used by the department of the brazilian government, IBGE, which is responsible for cartography etc. But you can download it here (ProGRID IBGE). You'll find the .gsb files here (C:\Program Files\Progrid\GridFiles).

SAD69 Original (SAD69_003.GSB)
SAD69 reviewed in 1996 (SAD96_003.GSB)

If I open in QGIS a shapefile originally created in ArcGIS in SAD69 and other in SIRGAS2000, also transformed from SAD69 to SIRGAS in ArcGIS, without activate OTF, I can see the displacement between them. But when I transform the ArcGIS-shapefile-SAD69 to SIRGAS2000 in QGIS, the QGIS is unable to show their displacement, even with OTF activated. Why does this happens with shapes transformed in QGIS?

And the last problem: The QGIS doesn't create properly the .prj file, both for SAD69 and SIRGAS2000, as exposed here:

SIRGAS2000

GEOGCS["GRS 1980(IUGG, 1980)",DATUM'''["D_unknown"''',SPHEROID["GRS80",6378137,298.257222101]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]]

And the correct one, from ArcGIS is:

GEOGCS["GCS_SIRGAS_2000",DATUM["D_SIRGAS_2000",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]]

SAD69:

GEOGCS["Australian Natl & S. Amer. 1969",DATUM["D_unknown",SPHEROID["aust_SA",6378160,298.25]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]]

And the correct one, from ArcGIS is:

GEOGCS["GCS_South_American_1969",DATUM["D_South_American_1969",SPHEROID["GRS_1967_Truncated",6378160.0,298.25]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],VERTCS["WGS_1984_Geoid",VDATUM["WGS_1984_Geoid"],PARAMETER["Vertical_Shift",0.0],PARAMETER["Direction",1.0],UNIT["Meter",1.0]]

Here are the original data that I'm working with. These data are mineral rights from Rio Grande do Sul State, south Brazil: Shapefiles in SAD69 Shapefiles in SIRGAS

I asked for help at the QGIS Forum. They've found the same problem and couldn't solve it. Thanks!!

Change History (2)

comment:1 by jef, 13 years ago

Description: modified (diff)

comment:2 by pcav, 13 years ago

Must Fix for Release: YesNo
Note: See TracTickets for help on using tickets.