scatteredInterpolant is not interpolating in all directions

Dear all,

I have data on an irregular grid that I want to interpolate to another irregular grid with a finer resolution using a (bi)linear method (the one I have found and using is scatteredInterpolant). I did a test where I interpolate my values in matrix A creating output B in 2D. Then I changed one grid point p in A to a very high value and did the same interpolation creating output C. Then I took C minus B and looked at the result. I was expecting a peak around p and then a symmetrical (square or circle) pattern around p. But what I found was an elongated blob as seen in attached image. Perhaps there is an easy answer to this but if needed I can include a test code for you later on.

Any comments?

Many thanks for your help,

Fredrik