Is the error mapping done by an artificial neural network? Years ago in a book of Ritter, Schulten, and Martinez about Self Organizing Neural Maps there was an account to solve the Mapping of angles in a robot arm to the yielded x-y positions. At least I remember to have that book in my office. I will look it up.

ADDED: As I see, the master of Self Organizing Maps himself, Teuvo Kohonen, has written about it:

http://books.google.de/books?id=e4ig...page&q&f=false

This seems to be a more contemporary article:

http://mhrg.if.uidaho.edu/papers/201...ic_SOFAMAP.pdf