[Proj] ACT Standard Grid (AGD66)

[Richard Greenwood]

On Mon, Apr 13, 2015 at 11:39 AM, Hermann Peifer <peifer at gmx.eu> wrote:

>
> About +towgs84=-129.19,-41.21,130.73,-.25,-.37,-.33,-2.96
>
> The EPSG database has pretty similar values for coordinate operations
> 1458 and 1665, see e.g. at
>
> http://epsg-registry.org/export.htm?wkt=urn:ogc:def:coordinateOperation:EPSG::1665
>
> These values are however given according to METHOD: Coordinate Frame
> Rotation. You'd need to revert the sign of the rotation values, as
> explained in
>
> https://trac.osgeo.org/proj/wiki/GenParms#towgs84-DatumtransformationtoWGS84
> ,
> so you should use
>
> +towgs84=-129.19,-41.21,130.73,.25,.37,.33,-2.96
>

If you reverse the sign then shouldn't it be:

+towgs84=129.19,41.21,-130.73,-.25,-.37,-.33,2.96

or am I missing what you are suggesting?

Rich



I am however not so sure if this will help you to get rid of a 200m offset.
>
> Hermann
>
> On 2015-04-13 17:31, Michel.Dastous at bentley.com wrote:
> > Hi,
> >
> > I’m currently trying to publish an Oracle dataset marked as SRID 82474
> > and cannot determine the proper proj4 init string corresponding to it.
> > I was able to extract the WKT definition from Oracle:
> >
> > /PROJCS["ACT Standard Grid (AGD66)", GEOGCS [ "Australian Geodetic 1966
> > ACT", DATUM ["AGD 66 ACT", SPHEROID ["Australian", 6378160,
> > 298.25],-129.19,-41.21,130.73,-.25,-.37,-.33,-2.96], PRIMEM [
> > "Greenwich", 0.000000 ], UNIT ["Decimal Degree", 0.01745329251994330]],
> > PROJECTION ["Transverse Mercator"], PARAMETER ["Scale_Factor",
> > 1.000086], PARAMETER ["Central_Meridian", 149.0092948333], PARAMETER
> > ["False_Easting", 200000.000000], PARAMETER ["False_Northing",
> > 4510193.4939], UNIT ["Meter", 1.000000000000]]/
> >
> > The best we have is:
> >
> > /+proj=tmerc +lon_0=149.0092948333 +k=1.000086 +x_0=200000
> > +y_0=4510193.4939 +ellps=aust_SA
> > +towgs84=-129.19,-41.21,130.73,-.25,-.37,-.33,-2.96 +units=m +no_defs
> <>/
> >
> > Unfortunately this produce a displacement of around 200 meters when
> >   reprojected to Bing coordinate system.
> >
> > Can anyone help?
> >
> > Thanks,
> >
> > Michel
> >
> >
> >
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> >
>
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-- 
Richard W. Greenwood, PLS
www.greenwoodmap.com
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