EGM96.java interpolation code is wrong

[samilkorkmaz]

In EGM96.java, method getOffset(), the interpolation portion has an error. To correct it, topRow and bottomRow indices have to be swapped when calling getPostOffset() function.

For details, see my blog post here: http://samilkorkmaz.blogspot.com/2016/03/error-in-nasa-code.html

[zglueck]

@samilkorkmaz Thanks for finding this one and the informative blog post! I just pushed commit 08e9201 which implements the fix you recommended and includes some unit testing to verify the getOffset method.