NTERPLATON(...,'fill'), if LAT and LON are matrices of the from output 
    by MESHGRID, will instead fill missing data points from the linear
    interpolation with the results of a bin-averaging.  
 
    This typically affects only a small number of points, but is useful in
    controlling exactly what constitutes missing data.  
 
    For example, when interpolating an ocean field from a finer grid to a 
    coaser grid, linear interpolation will result in somewhat degraded 
    continental boundaries. T