[Proj] PROJ.4: pj_transform parameters

[Doanh Hoang]

Hi David.

Thank you for quick support !

Is it right that for another datums (for example : NAD27, NAD83, OSGB, ED
50, etc,...) we can do transformation with only just simple initialization
like projPJ src= pj_init_plus( "+init=epsg:4326"); (I mean that we use only
+init parameter)

Clicking on http://spatialreference.org/ref/epsg/4326 I get :  " Not found,
/ref/epsg/4326. "

Doanh

On 4 October 2012 23:48, nicolas david <ericnico.david at gmail.com> wrote:

> Hi
>
> 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 code.
> Take care of setting the PROJ_LIB environnement variable to the correct
> path for your projection directory.
>
> Nicolas
>
>
> 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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>
>
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