[Qgis-user] Difference: EPSG 3004 - EPSG 102092

[Paolo]

Yes, actuallyI am reprojecting rasters from Gauss Boaga Roma 40 Monte 
Mario zone 2 to ED50UTM33.
Errors are huge if I use 102092, but they are very small using 3004.

Further research lead me to discover even more, appearingly identical, 
reference systems:
- Monte Mario Italy 2.prj (codice EPSG 3004);
- Monte Mario (Rome) Italy 2.prj (codice EPSG 26592);
- Roma 1940 Gauss Boaga Est.prj (codice EPSG 102094),

This is even more confusing, and will require some more studying.

Regards,
Paolo

Il 07/11/2013 10:37, G. Allegri ha scritto:
>
> As you can see, 102092 has the average transformation parameters to 
> WGS84, which brings some more precision during datum transformation. I 
> suppose you're reprojecting the data to some different CRS.
>
> giovanni
>
> Il 07/nov/2013 08:33 "Paolo" <e-paul at tiscali.it 
> <mailto:e-paul at tiscali.it>> ha scritto:
>
>     Oops... I forgot the most important part in my first post. Here
>     are the edfinitions:
>
>     EPSG 3004 - Monte Mario / Italy zone 2:
>     +proj=tmerc +lat_0=0 +lon_0=15 +k=0.9996 +x_0=2520000 +y_0=0
>     +ellps=intl +towgs84=-104.1,-49.1,-9.9,0.971,-2.917,0.714,-11.68
>     +units=m +no_defs
>
>     EPSG 102092 - Monte_Mario_Italy_2:
>     +proj=tmerc +lat_0=0 +lon_0=15 +k=0.9996 +x_0=2520000 +y_0=0
>     +ellps=intl +units=m +no_defs
>
>     3004 works well with my data, while 102092 does not.
>     There appears to be a relatively large shift, in the order of tens
>     or hundreds meters,monstly along the north - south direction.
>
>     Thanks
>     Paolo
>
>
>
>     Il 07/11/2013 00:47, G. Allegri ha scritto:
>>     In QGIS they appear having the same definition, Could you paste
>>     the 102092 definition that you have?
>>
>>     giovanni
>>
>>
>>     2013/11/6 Paolo <e-paul at tiscali.it <mailto:e-paul at tiscali.it>>
>>
>>         Hello,
>>         I am a relatively recent QGIS user. I am at the moment using
>>         version 2.0 - Dufour.
>>         I would like to ask a simple question about two different
>>         datums I am experiencing problems with.
>>         They are: EPSG 102092 and EPSG 3004.
>>         Accordinf to my (short) research, they  are supposed to be
>>         exactly the same datum, but the definitions in QGIS are
>>         different.
>>         If I use 3004, the specific data set I'm using will overlap
>>         properly with the other datasets, but it will not if I use
>>         102092.
>>         Can anybody help me getting a better understanding of this
>>         behaviour?
>>         Thanks
>>         Paolo
>>         _______________________________________________
>>         Qgis-user mailing list
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>>
>>
>>
>>
>>     -- 
>>     Giovanni Allegri
>>     http://about.me/giovanniallegri
>>     blog: http://blog.spaziogis.it
>>     GEO+ geomatica in Italia http://bit.ly/GEOplus
>

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