[OSRS-PROJ] WGS84 to RT90 problems..

[Johan Björk]

Clifford J Mugnier wrote:

>
>
>Johan
>
>Try reversing the sign of the rotation angles.  Your parameters may have
>been computed with the left-handed European rotation convention.  (That's
>one of the "inside" jokes in the international geodetic community, and the
>responsible parties on the continent refuse to admit their error).
>
>Cliff Mugnier
>LOUISIANA STATE UNIVERSITY
>--------------------------------
>Hi everyone
>Sorry to bother with a very newbie question (I assume)
>I've seen people trying todo the same thing in the archives but I'm
>still not able to get it right :c.
>
>I'm trying to convert from WGS84 to RT90 2.5G W 0:-15
>
>Feels like i've tried a zillion things but nothing gets me the correct
>results.
>
>I have a 7 param conversion params, Do I Need anything more?
>I use :
>"towgs84=-414.0978567149,-41.3381489658,-603.0627177516,-0.8550434314,2.1413465,-7.0227209516,1"
>as I got from http://www.lm.se/geodesi/refsys/sweref-rt/sweref99-rt90.htm
>sweref99 is ~same as WGS84.
>
>Any example on how to convert coordinates using the 7param conversion
>would be really nice
>
>I'm using values fetched from my gps and transformed online to compare
>the results :
>http://www.lm.se/geodesi/program/gtransrv/gtransframe.htm
>
>I'm using pj_transform with something like this (I've been changing this
>back and forth so many times, it's probably all wrong now, hoping to get
>a better example to work from)
>
>
>TIA
>
>PS: mails to list seems to work for me now, sry for all the extra posting
>
>
>/Johan Björk
>
>
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I tried this also, but I think i'm approaching this totaly wrong, I get 
very small diffrence when changing those values.

Here is the params i'm using :

char * from[] = {
        "proj=latlong",
        "datum=WGS84"
};


char *to[] = {
        "proj=tmerc",
        "ellps=bessel",
//      "towgs84=-414.0978567149,-41.3381489658,-603.0627177516,-0.8550434314,2.1413465,-7.0227209516,1",
        "towgs84=414.0978567149,41.3381489658,603.0627177516,0.8550434314,-2.1413465,7.0227209516,1",
        "lon_0=15d48'29.8\"E",
        "k=1.00",
        "y_0=0",
        "x_0=1500000",
        "units=m"
};
then pj_transform..

I'm sure i'm missing something big here, I just don't know what...

/Johan



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