Interpolation is done with a simple bi-linear algorithm.
Unfortunately the routine does not average from finer to coarser grids
yet, but really interpolates. There are some heuristics to check
whether a grid wraps in longitude, otherwise the last two points are
sometimes extrapolated slightly.
- Finest: select the grid with the smallest distance between
latitude or longitude values and interpolate the other grid to this
- Coarsest: select the grid that does not have the smallest gaps
and interpolate the other field to this one.
- First: interpolate to the grid of the field that was selected first.
- Second: interpolate to the grid of the field that was selected
on this page.
Interpolation turned out to be a very non-trivial problem. Please
report problems to me