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

[G. Allegri]

Exactly, that's what I was saying ;)

giovanni
Il 07/nov/2013 13:02 <b.j.kobben at utwente.nl> ha scritto:

> FWIW, the two definitions (EPSG 3004 & EPSG 102092) are NOT the same. They
> do have the same projection parameters, but one has datum shift parameters
> too (+towgs84=-104.1,-49.1,-9.9,0.971,-2.917,0.714,-11.68) that the other
> is lacking. That means that when you use the one in re-projecting data, it
> will be able to take into account the necessary datum-shift, while the the
> other will not be able to do that. In many cases this can lead to severe
> shifts in coordinates (up to several 100's of meters).
>
> Yours,
>
> --
> Barend Köbben
> ITC - University of Twente
> PO Box 217, 7500AE Enschede (The Netherlands)
> +31-(0)53 4874 253
> @barendkobben
>
>
>
>
>
>
> On 07-11-13 13:48, "G. Allegri" <giohappy at gmail.com> wrote:
>
> >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
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20131107/26df3560/attachment.html>