Thanks Nicolas and Rittri for very good support . <br><br>I already understand more detail about transformation and input parameters and the way to get them .<br><br>Thanks you very much !<br><br>Doanh<br><br><div class="gmail_quote">
On 5 October 2012 00:50, Mikael Rittri <span dir="ltr"><<a href="mailto:Mikael.Rittri@carmenta.com" target="_blank">Mikael.Rittri@carmenta.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF"><div>I think you must add a final slash after 4326 to make that link work.</div><div><br></div><div>Another site you could look at is <a href="http://www.epsg-registry.org" target="_blank"></a><a href="http://www.epsg-registry.org" target="_blank">http://www.epsg-registry.org</a></div>
<div><br></div><div>The +init usually works, but when the underlying datum isn't</div><div>WGS84, you<span> will not always get the best possible accuracy. </span></div><div>I believe the default implementation of OSGB36 isn't</div>
<div>very good, for example (it may have improved since</div><div>the last time I looked, though).</div><div><br></div><div>For ED50, I don't know any implementation that is good in</div><div>all of Europe/Middle East. The default has about 10 - 15 m</div>
<div>accuracy. If one needs higher accuracy, one must</div><div>choose an implementation that is tailor-made for a</div><div>smaller area, say Spain or some part of the North Sea. </div><div><br></div><div>Regards,</div><div>
<br></div><div>Mikael Rittri</div><div>Carmenta</div><div>Sweden</div><div><a href="http://www.carmenta.com" target="_blank">http://www.carmenta.com</a><br></div><div><br>4 okt 2012 kl. 19:07 skrev "Doanh Hoang" <<a href="mailto:doanh.hoang@mud-maps.com" target="_blank">doanh.hoang@mud-maps.com</a>>:<br>
<br></div><div><div class="h5"><div></div><blockquote type="cite"><div>Hi David. <br><br>Thank you for quick support !<br><br>Is it right that for another datums (for example : NAD27, NAD83, <span>OSGB, ED 50, etc,...) we can do transformation with only just simple initialization <br>
like projPJ src= pj_init_plus( "+init=epsg:4326"); (I mean that we use only +init parameter)<br>
<br></span>Clicking on <a href="http://spatialreference.org/ref/epsg/4326" target="_blank"></a><a href="http://spatialreference.org/ref/epsg/4326" target="_blank">http://spatialreference.org/ref/epsg/4326</a> I get : " Not found, /ref/epsg/4326.
"<span><br><br>Doanh<br></span><br><div class="gmail_quote">On 4 October 2012 23:48, nicolas david <span dir="ltr"><<a href="mailto:ericnico.david@gmail.com" target="_blank"></a><a href="mailto:ericnico.david@gmail.com" target="_blank">ericnico.david@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi<br><br>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 <br>
<br> projPJ src= pj_init_plus( "+init=epsg:4326"); <br><br>see <a href="http://spatialreference.org/ref/epsg/4326" target="_blank"></a><a href="http://spatialreference.org/ref/epsg/4326" target="_blank">http://spatialreference.org/ref/epsg/4326</a> for searching your projection code.<br>
Take care of setting the PROJ_LIB environnement variable to the correct path for your projection directory.<br>
<br>Nicolas<br><br><br><div class="gmail_quote">2012/10/4 Doanh Hoang <span dir="ltr"><<a href="mailto:doanh.hoang@mud-maps.com" target="_blank"></a><a href="mailto:doanh.hoang@mud-maps.com" target="_blank">doanh.hoang@mud-maps.com</a>></span><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div><div>
Hi all <br><br>Im developer and this is the first time I touch PROJ.4 . And I have following problem , please anyone can give me an advice:<br><br>In my project I need to do <b>transformation from datums (US, North America, UK, South Africa, New Zealand) to WGS84. </b><br>
<br>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.<br> <br>For example : following code that I found in internet : <br>
------------------------------------------------------------------------------------------------------<br> 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");<br>
projPJ dst= pj_init_plus("+proj=latlong +datum=WGS84 +ellps=WGS84");<br> double x,y,z;<br> x=100;<br> y=100;<br> z=100;<br> pj_transform(src,dst,1,1,&x,&y,NULL);<br>------------------------------------------------------------------------------------------------------<br>
<table style="border-collapse:collapse;width:640pt" border="0" cellpadding="0" cellspacing="0" width="640">
<colgroup><col style="width:640pt" width="640">
</colgroup><tbody><tr style="min-height:15.0pt" height="15">
<td style="min-height:15.0pt;width:640pt" height="15" width="640">params for initionlization of datums<br>+proj=merc
+ellps=clrk66 +lat_ts=33</td>
</tr>
<tr style="min-height:15.0pt" height="15">
<td style="min-height:15.0pt" height="15">+proj=latlong +ellps=clrk66</td>
</tr>
</tbody></table>
------------------------------------------------------------------------------------------------------<br>There are so many geospatial knowledge neccessary to understand these parameter. <br>Im developer and I know just only the simple name of datums(WGS84, NAD27, NAD83, etc,..) and coordinates of points, <br>
<br>With them how I can make transformation between different datums ? <b>Where I can get input parameters and define correct geospatial input parameters.</b><br><br>I very need your help. Thanks a lot. <br><span><font color="#888888"><br>
Hoang Doanh<br>
<br>
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