[OSRS-PROJ] Re:

[Bart Adriaanse]

Eugene,

The exact projection definition in MapInfo is quite obscure, by checking
mapinfo.prj and looking at the definitions, i find that MapInfo (6.5) uses
NAD27 datum by default for mercator as opposed of WGS84 you specified to
Proj. You would have to modify mapinfo.prj to change this to WGS84

Unfortunately the documentation for the MapInfo datum definition codes has
become pretty obscure too, here's the only place where i can find it, is
suppose MapBasic documentation might help too.

http://testdrive.mapinfo.com/mapxhelp/map00772.htm
http://testdrive.mapinfo.com/mapxhelp/map00035.htm

Maybe you can check if this solves the puzzle ?

Good luck,

Bart Adriaanse


----- Original Message -----
From: "Eugene Shebeko" <shebeko at mail.ru>
To: <osrs-proj at remotesensing.org>
Sent: Tuesday, August 20, 2002 6:19 PM


> Hi.
> Why conversion from Lat\Long to mercator are some different in proj4 and
> mapinfo.
>
> int fwd(double &x,double &y)
> {
>     projUV d;
>     d.u=x*DEG_TO_RAD;
>     d.v=y*DEG_TO_RAD;
>     d=pj_fwd(d,handle);
>     if(d.u==HUGE_VAL)
>       return -1;
>     x=d.u;
>     y=d.v;
>     return 0;
> }
>
> char* v[]={"proj=merc","ellps=WGS84","lon_0=0E"};
> int c=sizeof(v)/sizeof(char*);
>
> handle=pj_init(c,v);
>
> x=30.524608;y=50.412181;
> fwd(x,y);
>
> I get
> x=3397983.8192243
> y=6485018.0866892
> but in MapInfo I get
> x=3397798.14
> y=6485002.45
> so difference between conversion is
> dx=185.67
> dy=15.63
> How can I fix it?
>
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