Thanks for the informations.
The two reference systems are often referred to as being identical, and
that lead me to believing so.
If I understand well, the datum shift parameters are required in order
to improve the accuracy of the conversion between 3004 and other RS as
ED50 UTM33, while they are not needed for conversion between 102092 and
e.g. WGS84?
Sorry if post was off topic as non strictly QGis related.
Regards
Paolo
Il 07/11/2013 13:54, G. Allegri ha scritto:
Exactly, that's what I was saying ;)
giovanni
Il 07/nov/2013 13:02 <b.j.kob...@utwente.nl
<mailto:b.j.kob...@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" <gioha...@gmail.com
<mailto:gioha...@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-p...@tiscali.it <mailto:e-p...@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-p...@tiscali.it
<mailto:e-p...@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-p...@tiscali.it <mailto:e-p...@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
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>
>
>
>
>
>
>--
>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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