<div>Hi Hugo </div>
<div> </div>
<div>Thanx for your reply.</div>
<div> </div>
<div>So what should be the projection definition then .. to make it general..???</div>
<div> </div>
<div>I am trying to convert the geographical co-ordinates to screen co-ordinates ..</div>
<div>so i require to convert the lat/lon to some projection and the convert that X,Y to pixels...</div>
<div>hope this is correct ...</div>
<div> </div>
<div>or is there some function in proj4/or anywhere else which does this ....??</div>
<div> </div>
<div>Thanx again</div>
<div> </div>
<div>sandeep</div>
<div><br><br> </div>
<div><span class="gmail_quote">On 10/6/06, <b class="gmail_sendername">Hugo Tyson</b> <<a href="mailto:Hugo.Tyson@cpslocates.com">Hugo.Tyson@cpslocates.com</a>> wrote:</span>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid"><a href="mailto:proj-bounces@lists.maptools.org">proj-bounces@lists.maptools.org</a> <> wrote:<br>> I want to transform ... this lat/lon
39.739/-104.985...<br>> to world mercator project ..with the defintition<br>><br>> World Mercator <54004> +proj=merc +latts=0 +lon0=0<br>> +k=1.000000 +x0=0 +y0=0 +ellps=WGS84 +datum=WGS84 +units=m no_defs <>
<br>><br>> but the method gives an "error"....<br>><br>> this method works fine if i give lat/lon say 42.4182,-74.2643<br><br>I've not heard of "world mercator", but looking at the parameters
<br>it's projecting into a plane tangent to the sphere at lat 0, lon 0.<br>So it only works for longitudes from -90 to +90 (though these map<br>to infinities in the projected plane).<br><br>Your example of -104 longitude is around the back of the earth,
<br>on the "far side" from the projection plane. Therefore a<br>line from the origin through the point never intersects the<br>projection plane, so no result can be calculated. Hence your<br>error. Lon -74 is in range, so it's OK.
<br><br>HTH,<br> - Huge<br><br><br>--<br>Hugo Tyson, Cambridge Positioning Systems Ltd<br>=************************************************************<br>********************************************************************************
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