Interpolate using linear approximation
        Returns the same as interpolate(lons,lats,data,order=1)

def interpolate_linear(self, lons, lats, data):
        """
        Interpolate using linear approximation
        Returns the same as interpolate(lons,lats,data,order=1)
        """
        return self.interpolate(lons, lats, data, order=1)