Hello, I'm building an application in which I need to obtain the magnetic latitude for use in another calculation. There are many website online that can calculate this for you, mostly point and click on a map, or enter your latitude and longitude into a form. But I'm wondering how they actually calculate this value? And if it's something difficult to implement into my program. If anyone knows how I could go about figuring out how to do this, or any resources that might help, it would be most appreciated.