# How is the error of FindGeometricTransform calculated? [duplicate]

How is the returned error calculated?

I cannot find any information about this in the documentation of FindGeometricTransform.

It is only indicated:

"FindGeometricTransform returns an expression of the form {err,trfun}, where err is an estimate of the average alignment error, and trfun is a transformation function."

## marked as duplicate by Michael E2, m_goldberg, Henrik Schumacher, kirma, bbgodfreyJan 15 at 5:23

It is the mean Euclidean distance of the points after transformation.

{err, transform} = FindGeometricTransform[data2, data1];
err


0.315546

Mean@MapThread[EuclideanDistance, {transform@data1, data2}]


0.315546

• This is great. Form where did you find the information? – mrz Jan 9 at 22:02
• I just worked it out. There were only so many ways it could be done, and mean euclidean distance seemed to make the most sense – Carl Lange Jan 9 at 22:19
• I would be happy to get an additional comment regarding EuclideanDistance : in my question mathematica.stackexchange.com/questions/189124/… is a comment from me below Cesareos answer. What is your opinion about that? – mrz Jan 10 at 15:38
• 4000 km??? Incredible. – mrz Jan 10 at 15:45
• I'll answer your EuclideanDistance question on that question. Also, thanks a lot, it's really been an amazing project! Do check out toughsoles.ie if you're interested :) – Carl Lange Jan 10 at 18:05