<div dir="ltr"><div><div><div>Adam<br><br></div>I think you have to change the order of your coordinates. The default input for PROJ is (lon,lat) and the default output is (Easting,Northing).<br>I used PROJ in the command line to check.<br>
<br>You have done:<br><span style="font-family:courier new,monospace">echo 51.5072 0.1275 | proj +proj=merc +a=6378137 +b=6378137<br>5733755.28      14193.25</span><br><br></div><div>and it should have been:<br><span style="font-family:courier new,monospace">echo 0.1275 51.5072 <span class="skype_c2c_container" dir="ltr" tabindex="-1" onmouseover="SkypeClick2Call.MenuInjectionHandler.showMenu(this, event)" onmouseout="SkypeClick2Call.MenuInjectionHandler.hideMenu(event)"><span class="skype_c2c_highlighting_inactive_common" dir="ltr"><span class="skype_c2c_textarea_span"><span style="font-family:courier new,monospace"><span class="skype_c2c_text_span"></span></span><span class="skype_c2c_free_text_span"></span></span></span></span> | proj +proj=merc +a=6378137 +b=6378137<br>
</span></div><div><span style="font-family:courier new,monospace">14193.24        6711506.71<br></span><br></div><div>The local deformation of lengths at latitude LAT is approximately 1/COS(LAT)<br><br>Regards<br></div><br>
</div>José Gonçalves<br><br><div><div><br><br></div></div><div onmouseout="SkypeClick2Call.MenuInjectionHandler.hideMenu(event)" onmouseover="SkypeClick2Call.MenuInjectionHandler.showMenu(this, event)" style id="skype_c2c_menu_container" class="skype_c2c_menu_container">
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</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">2014-02-24 13:30 GMT+00:00 AdamDynamic <span dir="ltr"><<a href="mailto:helloadamdynamic+proj4@gmail.com" target="_blank">helloadamdynamic+proj4@gmail.com</a>></span>:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Ah ok, thanks for that. Reading your answer, the notation makes a bit more<br>
sense (a risk of using something you find on the internet without actually<br>
understanding it)<br>
<div class=""><br>
<br>
> To output the map onto 900x1100 rectangle you have to scale the length<br>
> and width of your projected map coordinates to 900 and 1100. And then<br>
> you have to apply shift of origin of course.<br>
<br>
</div>Am I correct in thinking that as I have the latitude of true scale as the<br>
Equator, then no shift of origin is required?<br>
<br>
In terms of scaling the output, my understanding is that the 'corners' of a<br>
projection based on latitude and longitude should be -180,-90 and 180,90 -<br>
when I convert these values using the PyProj library I get values of 1E30<br>
for each value (which seems to me clearly wrong). What is the best way to<br>
scale the output in terms of min/max values (in 'pseudo-meters') for each<br>
corner of my 900x1100 rectangle?<br>
<br>
Thanks again for the help!<br>
<br>
Adam<br>
<br>
<br>
<br>
<br>
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