Really Easy Coordinate Transformation

4 Jan, 2009 geospatial, open source, technology, web

One of the most frequent questions I get from clients is how to transform lat/long to LCC coordinates in a very lightweight fashion, in their webapps. There are many solutions and approaches under the MetaCRS umbrella to choose from, depending on your requirements.

Here’s a super lightweight way to do it with proj4js:

<script src="http://svn.osgeo.org/metacrs/proj4js/trunk/lib/proj4js-compressed.js"></script>
<script src="http://svn.osgeo.org/metacrs/proj4js/trunk/lib/defs/EPSG42304.js"></script>

...

var x = -75.0;
var y = 45.0;
var p = new Proj4js.Point(x,y);
Proj4js.transform(new Proj4js.Proj("EPSG:4326"), new Proj4js.Proj("EPSG:42304"), p);
alert(p.x + " " + p.y);

Done! Kudos to Mike Adair et. al.!

2 Comments so far »

Howard Butler said,

Wrote on January 4, 2009 @ 19:59:27

Mozilla Firefox 3.0.5 Mac OS X 10
Do people normally link out of OSGeo’s SVN for doing Proj4js stuff rather than caching their own local copy?
Posted from United States
Mozilla Firefox 3.0.5 Mac OS X 10
tomkralidis said,

Wrote on January 4, 2009 @ 20:23:32

Mozilla Firefox 3.0.4 Mac OS X 10
Some people (those of us who live off proof of concepts/demos) live on the edge 🙂

Yes, good point. Folks would want to fetch a local copy (latest stable for that matter) for performance and stable codebase.
Posted from Canada
Mozilla Firefox 3.0.4 Mac OS X 10