I try to perform an interpolation on 3D scattered data (data that is gathered on a 3D irregular mesh grid) to a regular gridded sphere. This means that the data is periodic in two angles (elevation and azimuth). As I need smooth data, I prefer using the natural interpolation. For the interpolation, I use 'TriScatteredInterp' (Matlab 2012a). I do not only use two angles, but also the radius, as the scattered data also has a slight radial variation (which might be important for further processing). As a result, I get NaN's around the poles (elevation equals 0 and pi) and at zero azimuth. Are there any 'quick' workarounds to use the periodic behavior of the data or other tricks to avoid these NaN's and get a continuous result over the entire sphere, also at the poles and zero azimuth?