[MetaCRS] RE: CS-Map: info about EUROP50-7P, a 7-parameter ED50-to-WGS84 datum shift?

[Melita Kennedy]

Mikael,

I received those parameters as part of set of Portugal transformations
from the ESRI distributor who had them from Eng. Jorge Teixeira Pinto
at the Portuguese Institute of Cartography (IPCC). This was around
2000. The current transformation from IGP for ED50/WGS84 is in EPSG
(and ESRI) as code 1989 (ED 1950 to WGS 1984 #34). At least using the
parameters listed in:

http://www.igeo.pt/produtos/Geodesia/Inf_tecnica/parametros_transformacao/ParamTransf_CONTINENTE.pdf

I don't have any accuracies for the data from 2000.I doubt this
transformation is supposed to cover any country but Portugal.

Sincerely,
Melita

-- 
Melita Kennedy
Product Engineer
ESRI, Inc.

> Date: Tue, 3 Feb 2009 11:53:20 -0800
> From: Norm Olsen <norm.olsen at autodesk.com>
> Subject: [MetaCRS] RE: CS-Map: info about EUROP50-7P, a 7-parameter
>        ED50-to-WGS84 datum shift?
> To: Mikael Rittri <Mikael.Rittri at carmenta.com>,
>        "metacrs at lists.osgeo.org"       <metacrs at lists.osgeo.org>
>
> Hello Mike . . .
>
> Yes, you got the correct list.
>
> The definition in question was added to the dictionaries by an employee who is no longer with us, so there is no resource to refer to other than the Portuguese authority or ESRI.  It sure looks like a simple typo by someone.
>
> I did find the following: http://www.asprs.org/resources/grids/04-2002-portugal.pdf
>
> May quick look did not find any 7 parameter definitions, but it did have an promising reference (although it appears to be seven years old):
>
> Thanks go entirely to Jorge Teixeira
> Pinto, director of Geodetic Services,
> Instituto Portugués de Cartografia e
> Cadastro.
>
> At ESRI, the person to contact is Melita Kennedy.  She might be able to provide a degree of confidence that the ESRI definition is correct.
>
> Norm
>
> -----Original Message-----
> From: metacrs-bounces at lists.osgeo.org [mailto:metacrs-bounces at lists.osgeo.org] On Behalf Of Mikael Rittri
> Sent: Tuesday, February 03, 2009 5:47 AM
> To: metacrs at lists.osgeo.org
> Subject: [MetaCRS] CS-Map: info about EUROP50-7P, a 7-parameter ED50-to-WGS84 datum shift?
>
> Hello,
> sorry if this is the wrong mailing list for my question.
>
> I found the following datum shift for ED50 to WGS84 in CS-Map\Dictionaries\datums.asc:
>
> DT_NAME: EUROP50-7P
>        DESC_NM: European 1950, mean Values (7 Parameter Transform)
> # aka ED50, ED 50
> # Used for Austria, Belgium, Denmark, Finland, France, W. Germany, Gibraltar, Greece
> # Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland
>        SOURCE: IPCC - Instituto Português de Cartografia e Cadastro
>        ELLIPSOID: INTNL
>     USE: 7PARAMETER
>        DELTA_X: -66.863
>        DELTA_Y: -134.888
>        DELTA_Z: -111.49
>        ROT_X: 0.53
>        ROT_Y: 0.14
>        ROT_Z: -0.57
>        BWSCALE: -3.4
>
> which looked interesting, since I couldn't find it in the EPSG's database.
> (The only EPSG shifts for ED50 over such a large area are 3-parameter
>  transforms taken from US DMA TR8350.2:
>  - "ED50 to WGS 84 (1)" with the same area of use, and accuracy 10 m,
>  - "ED50 to WGS 84 (2)", with a smaller area of use, and accuracy 6 m,
>  the accuracy here is the one-sigma error.)
>
> But I didn't find the accuracy of the 7-parameter transform in the CS-Map
> sources.  So I tried to find the Portuguese original source, without success.
>
> However, I did find a similar transform in ArcGIS, called ED_1950_To_WGS_1984_PT7,
> ( http://gis.sfsu.edu/helpdesk/arcmap/projections/Map_Projection_Tables.pdf ),
> which is identical to the CS-Map version, except that
>    dX = -68.863 (not -66.863 as in CS-Map).
>
> So, it seems that either ArcGIS or CS-Map has the wrong value for dX, but I don't
> know which one.
>   I realize that the result of using the wrong dX is probably less than the method
> accuracy, but I would still like to know which one is correct.
>   More important, I would really like to know the method accuracy (preferably
> both the one-sigma error and the maximal error, if the original source gives them).
>
> Best regards,
> --
> Mikael Rittri
> Carmenta AB
> SWEDEN
> www.carmenta.com
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