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

[G. Allegri]

Roma 1940 Gauss Boaga is different in that it as a different central
meridian.
The other two are different definitions of the same datum, but in 3003
there re the average transformation parameters. That's why it works better
then 102094.
In the previous email I inverted the two.

giovanni


2013/11/7 Paolo <e-paul at tiscali.it>

>  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> 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>
>>
>>> 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
>>> Qgis-user at lists.osgeo.org
>>> http://lists.osgeo.org/mailman/listinfo/qgis-user
>>>
>>
>>
>>
>>  --
>> Giovanni Allegri
>> http://about.me/giovanniallegri
>> blog: http://blog.spaziogis.it
>> GEO+ geomatica in Italia http://bit.ly/GEOplus
>>
>>
>>
>


-- 
Giovanni Allegri
http://about.me/giovanniallegri
blog: http://blog.spaziogis.it
GEO+ geomatica in Italia http://bit.ly/GEOplus
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