[Proj] UTM32N-GaussBoaga datum shift problems

[Giorgio Agugiaro]

Hi everybody!
First of all, happy 2007! ;-)

Before you "enjoy" this long mail, I summarise it here.
I have some troubles with datum-shift results using cs2cs.
I am using proj 4.50 compiled on a Mandriva 2007 box.

Am I doing something wrong? Could please someone help?
Thanks in advance for any help and/or suggestions!!

Giorgio Agugiaro
(giorgio.agugiaro at unipd.it)


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

So, to the topic:
I need to set up proj in order to use it for a datum shift from Grass GIS
via r.proj and v.proj.
I calculated (and checked the results with other programs) the 7 parameters
from the following test points:

WGS84-UTM32N
Northing    |   Easting | h_ell| Point_id
-----------------------------------------
5022649.211  718871.227  52.537  #1000
5022602.837  718852.690  52.096  #4000
5022584.125  718899.004  52.027  #5000
5022565.657  718945.481  51.732  #6000
5022519.163  718926.858  51.777  #8000
5022519.189  718872.883  51.556  #9000
5022500.582  718919.424  51.651  #10000

Roma40, Zone 1 (GaussBoaga)
Northing    |    Easting  | h_orto | Point_id
-------------------------------------------------------
5022670.5000  1718900.5000  12.00000 #1000
5022624.1156  1718881.9935  11.56889 #4000
5022605.4286  1718928.3421  11.50839 #5000
5022587.0136  1718974.8102  11.21289 #6000
5022540.5104  1718956.2347  11.26078 #8000
5022540.4791  1718902.2595  11.03863 #9000
5022521.9201  1718948.8186  11.13414 #10000

calculated 7 parameters are (deltax m, deltay m,deltaz m,rx sec,ry sec,rz
sec,scale_factor ppm):
-927.3934,-426.678,166.8859,-129.10138,-5.11282,-118.30878,65.7674

In order to check the transformation I do:

cs2cs -rsf %.4f +datum=WGS84 +proj=utm +zone=32 +north +unit=m +to
+ellps=intl
     +proj=tmerc +lat_0=0.0 +lon_0=9.0 +k=0.9996 +x_0=1500000 +y=0.0 +unit=m
     +towgs84=-927.3934,-426.678,166.8859,-129.10138,-5.11282,-118.30878,65.
7674 mg84grid.txt

(file mg84grid.txt contains the WGS84-UTM32N coordinates shown above)
Output is:
5022672.0592    1718901.5497 12.1290
5022625.6723    1718883.0528 11.6925
5022607.0004    1718929.3798 11.6276
5022588.5726    1718975.8696 11.3367
5022542.0656    1718957.2869 11.3862
5022542.0462    1718903.3151 11.1629
5022523.4795    1718949.8690 11.2620

As you can see, Delta_N is about 1.5 m and a Delta_E is about 1 m.
These parameters generally allow me to get datum-shifted values with (more
or less) cm delta_N and delta_E.

So, where am I doing something wrong?

On a side note, I used successfully cs2cs in a similar datum-shift with
these test points and parameters:

Points
AA   WGS84-UTM32N                 45 24 05.7680 N   11 52 02.5800 E   59.57
     Gauss Boaga Roma40           45 24 03.3760 N   11 52 03.3920 E
BB   WGS84-UTM32N                 45 16 25.1360 N   12 02 50.4560 E   48.58
     Gauss Boaga Roma40           45 16 22.7553 N   12 02 51.2230 E
CC   WGS84-UTM32N                 45 13 34.9090 N   11 32 03.5180 E   59.81
     Gauss Boaga Roma40           45 13 32.5269 N   11 32 04.3701 E
DD   WGS84-UTM32N                 45 30 37.6240 N   11 37 36.3980 E   74.00
     Gauss Boaga Roma40           45 30 35.2256 N   11 37 37.2298 E
EE   WGS84-UTM32N                 45 07 10.2550 N   11 35 25.8400 E   52.32
     Gauss Boaga Roma40           45 07 07.8739 N   11 35 26.6984 E

calculated 7 parameters were (units as above):
-135.9406,-28.3596,-10.6462,-0.24989,-2.48329,-1.57131,-15.6918

resulting transformed points differed about 20/30 cm.
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