[Proj] PROJ.4: pj_transform parameters

nicolas david ericnico.david at gmail.com
Thu Oct 4 11:48:49 EST 2012


On our proj4 installation you should have a directory call "nad". This
directory have some dictionnary of projection that could be used to define
projection parameters. For exemple with the lat/long wgs84 projection you
could use

projPJ src= pj_init_plus( "+init=epsg:4326");

see http://spatialreference.org/ref/epsg/4326 for searching your projection
Take care of setting the PROJ_LIB environnement variable to the correct
path for your projection directory.


2012/10/4 Doanh Hoang <doanh.hoang at mud-maps.com>

> Hi all
> Im developer and this is the first time I touch PROJ.4 . And I have
> following problem , please anyone can give me an advice:
> In my project I need to do *transformation from datums  (US, North
> America, UK, South Africa, New Zealand) to WGS84. *
> After having a look at defintion of pj_transform  (function to do datums
> transformation on PROJ.4). I have seen that there are so many input
> parameters.
> For example : following code that I found in internet :
> ------------------------------------------------------------------------------------------------------
>     projPJ src= pj_init_plus("+proj=tmerc +lat_0=38N +lon_0=128E
> +ellps=bessel +x_0=400000 +y_0=600000 +k=0.9999
> +towgs84=-146.43,507.89,681.46");
>     projPJ dst= pj_init_plus("+proj=latlong +datum=WGS84 +ellps=WGS84");
>     double x,y,z;
>     x=100;
>     y=100;
>     z=100;
>     pj_transform(src,dst,1,1,&x,&y,NULL);
> ------------------------------------------------------------------------------------------------------
>   params for initionlization of datums
> +proj=merc +ellps=clrk66 +lat_ts=33  +proj=latlong +ellps=clrk66 ------------------------------------------------------------------------------------------------------
> There are so many geospatial knowledge neccessary to understand these
> parameter.
> Im developer and I know just only the simple name of datums(WGS84, NAD27,
> NAD83, etc,..) and coordinates of points,
> With them how I can make transformation between different datums ? *Where
> I can get input parameters and define correct geospatial input parameters.
> *
> I very need your help. Thanks a lot.
> Hoang Doanh
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