[GRASS-user] point reprojection: v.proj vs cs2cs results

[ivan marchesini]

Dear Users,

I need to reproject a point (280799|4802457) from location A to location
B

these are the PROJ_INFO files:
_______________________
LOCATION A (UTM ED50)

name: UTM
datum: eur50
towgs84: -87.000,-98.000,-121.000
proj: utm
ellps: international
a: 6378388.0000000000
es: 0.0067226700
f: 297.0000000000
zone: 33
______________________

and
______________________
Location B (Gauss-Boaga EST Rome40)

name: Transverse Mercator
datum: rome40
towgs84: -104.1,-49.1,-9.9,0.971,-2.917,0.714,-11.68
proj: tmerc
ellps: international
a: 6378388.0000000000
es: 0.0067226700
f: 297.0000000000
lat_0: 0.0000000000
lon_0: 15.0000000000
k_0: 0.9996000000
x_0: 2520000.0000000000
y_0: 0.0000000000
__________________


if I try to use v.proj for the point, from location A to Location B,
I obtain this coordinate (into location B):
2300732.60711273|4802279.27423501

--------------------------------------

Instead, if I use cs2cs:

echo "280799 4802457 263" | cs2cs -v +init=epsg:23033 +to +proj=latlong
+datum=WGS84 |cs2cs -v +proj=latlong +datum=WGS84 +to +init=epsg:3004
+towgs84=-104.1,-49.1,-9.9,0.971,-2.917,0.714,-11.68

(where:

cat /usr/share/proj/epsg | grep Italy -A1 | grep "zone 2" -A1
# Monte Mario / Italy zone 2
<3004> +proj=tmerc +lat_0=0 +lon_0=15 +k=0.999600 +x_0=2520000 +y_0=0
+ellps=intl +units=m +no_defs  <>

and 

cat /usr/share/proj/epsg | grep UTM -A1 | grep ED50 -A1 |grep 33 -A1
# ED50 / UTM zone 33N
<23033> +proj=utm +zone=33 +ellps=intl +units=m +no_defs  <>
)

I obtain this output:

# ---- From Coordinate System ----
#Lat/long (Geodetic)
#
# +proj=latlong +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0
# ---- To Coordinate System ----
#Transverse Mercator
#       Cyl, Sph&Ell
# +init=epsg:3004 +towgs84=-104.1,-49.1,-9.9,0.971,-2.917,0.714,-11.68
# +proj=tmerc +lat_0=0 +lon_0=15 +k=0.999600 +x_0=2520000 +y_0=0
+ellps=intl
# +units=m +no_defs
# ---- From Coordinate System ----
#Universal Transverse Mercator (UTM)
#       Cyl, Sph
#       zone= south
# +init=epsg:23033 +proj=utm +zone=33 +ellps=intl +units=m +no_defs
# ---- To Coordinate System ----
#Lat/long (Geodetic)
#
# +proj=latlong +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0
2300810.30      4802292.11 425.44

As you can see the resulted coordinate is quite different from the
previous one...

can someone explain me this strange result???
surely it is my fault, but I can't understand where I'm wrong

Thanks

Ivan



-- 
Ivan Marchesini
Department of Civil and Environmental Engineering
University of Perugia
Via G. Duranti 93/a 
06125
Perugia (Italy)
e-mail: marchesini at unipg.it
        ivan.marchesini at gmail.com
tel: +39(0)755853760
fax: +39(0)755853756
jabber: geoivan73 at jabber.org