[Proj] PROJ.4: pj_transform parameters

[Doanh Hoang]

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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