Comments on: Introduction to Mercator Projections, Latitude and Longitude http://flashlabs.wordpress.com/2011/03/05/introduction-to-mercator-projections-latitude-and-longitude/ Swingpant's Code Nurdlings Thu, 08 Nov 2012 04:03:00 +0000 hourly 1 http://wordpress.com/ By: Alex Nino http://flashlabs.wordpress.com/2011/03/05/introduction-to-mercator-projections-latitude-and-longitude/#comment-497 Mon, 05 Sep 2011 10:18:45 +0000 http://swingpants.com/?p=360#comment-497 Hi! this is quite interesting, a while ago I’ve been working in a project (PeopleMundi for playbook and android) and I was facing a situation similar to this, I found similar approaches like convertLatLonTo3DPos, and unfortunatelly they are very slow in term of performance… instead I end up using a provisional stencil buffer which works about 10x times faster by making the reverse 3d projection equation. have a look on it in action http://www.yoambulante.com/en/labs/FixPlanetEarth/ the playbook and android version runs at solid 30fps using this technique, I hope it helps, looking forward to have a beer at FOTB11, cheers!

]]> By: dotNetFollower http://flashlabs.wordpress.com/2011/03/05/introduction-to-mercator-projections-latitude-and-longitude/#comment-447 Sat, 30 Jul 2011 19:53:56 +0000 http://swingpants.com/?p=360#comment-447 Hello!

I use the pure mathematical method to convert Mercator Sphere coordinates to latitude and longitude.

I needed it in JavaScript and implemented it in the following way:
function MercatorToLatLon(mercX, mercY) {

var rMajor = 6378137; //Equatorial Radius, WGS84
var shift = Math.PI * rMajor;
var lon = mercX / shift * 180.0;
var lat = mercY / shift * 180.0;
lat = 180 / Math.PI * (2 * Math.atan(Math.exp(lat * Math.PI / 180.0)) – Math.PI / 2.0);

return { ‘Lon’: lon, ‘Lat’: lat };
}
You can read it up in my blog (http://dotnetfollower.com/wordpress/2011/07/javascript-how-to-convert-mercator-sphere-coordinates-to-latitude-and-longitude/) at greater length.

Thanks!

]]> By: swingpants http://flashlabs.wordpress.com/2011/03/05/introduction-to-mercator-projections-latitude-and-longitude/#comment-347 Sat, 05 Mar 2011 21:30:19 +0000 http://swingpants.com/?p=360#comment-347 I shall be expanding on MP in future posts.

For expediency here is a raw projection:

new Point(point.x, Math.log(Math.tan(0.25 * Math.PI + 0.5 * point.y)));

and the raw un-projection:

new Point(point.x, 2 * Math.atan(Math.pow(Math.E, point.y)) – 0.5 * Math.PI);

For more mathematical detail see: http://mathworld.wolfram.com/MercatorProjection.html

]]> By: makc http://flashlabs.wordpress.com/2011/03/05/introduction-to-mercator-projections-latitude-and-longitude/#comment-346 Sat, 05 Mar 2011 15:07:39 +0000 http://swingpants.com/?p=360#comment-346 Due to limited bandwidth we had to omit Mercator projection itself from the post. Management.

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